PHD-Chemistry

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    Fabrication of Rapid Diagnostic Kit Casing Using Modified Biodegradable Paper Materials as an Alternative to Plastic
    (Kenyatta University, 2019-07) Mwangi. James Njogu
    The high population growth rate, emerging diseases and high cost of health care in developing countries has led to the high demand of rapid diagnostic test (RDT) kits. Rapid diagnostic test kits are medical devices used in early detection of diseases among the population living in areas with limited medical facilities. The portability and reliability of kits reduces medical cost incurred by inaccurate disease diagnosis. To meet this demand plastics are enormously produced as basic raw material in production of the kits. Plastics are often preferred because they are cheaper than their corresponding biopolymer. The most devastating menace from plastic is its high solid waste accumulation due to slow biodegradation. The study sought to modify selected paper materials and tree barks to mimic plastic properties to replace plastic in rapid diagnostic test kits. The selected papers were purchased from Nairobi County (Kenya) shops while selected tree barks were collected from farms within Kiambu County (Kenya). On modification with trichloro (lH, IH, 2H, 2H perfluorooctyl) silane at different reaction times insitu, the paper and polished tree barks surfaces displayed water contact angles between 90.14° to 144.60°, which indicated they were hydrophobic. The tree barks were however discontinued for further analysis due the limitation of cutting tools available. The modified paper did not attain superhydrophobicity since the water droplets placed on its tilted surface remained sticky rather than rolling as expected with superhydrophobic surfaces. The surface energy of modified paper materials displayed low critical surface energy values ranging from 27.9 to 40.0 dynes/em. The tensile strength of the unmodified and modified selected paper did not show any significant difference at P
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    Identification and Mechanisms of Allelochemicals Regulating Root-Knot Nematode Parasitism
    (Kenyatta University, 2023-10) Kihika, Ruth Muthoni; Margaret M. Ng'ang'a; David P. Tchouassi; Baldwyn Torto
    Global crop production is hampered by numerous pests and parasites including plant parasitic nematodes (PPNs). Root-knot nematodes (RKNs; Meloidogyne spp.) are among the most pervasive economically important PPNs accounting for crop losses of over USD 100 billion globally, thus posing a severe risk to food security. Despite the current measures deployed in the management of RKNs, their damage still persists, necessitating more effective approaches. Recent studies identified constitutive plant compounds that influence the host seeking behavior of RKNs. The current study sought to elucidate the chemical dialogue between host plants and RKNs during parasitism and investigate the chemical mechanisms of non-host plants in reducing nematode infestation. The influence of the infective stage juveniles (J2) of RKNs in inducing tomato (Solanum lycopersicum) root and leaf volatiles, and chemotactic effects on conspecifics was investigated. The hypothesis that the non-host Asteraceae plant vegetable black-jack (Bidens pilosa) suppresses infection of the PPN Meloidogyne incognita, in two susceptible Solanaceae host plants; tomato (Solanum lycopersicum) and black nightshade (S. nigrum) was also tested. In behavioral olfactometer assays, J2 avoided roots of 2-day infected plants but preferred 7-day infected tomato compared to healthy plants. Coupled gas chromatography-mass spectrometry (GC/MS) was used to identify root and leaf volatiles from healthy and RKN-infected tomato at two and seven-days post infection. Chemical analysis showed a two- to seven-fold increase in the amounts of monoterpenes emitted from tomato roots infected with M. javanica relative to healthy roots. Additionally, infected plants released ~4 to 225-fold quantitatively more leaf volatiles, and were compositionally richer than the healthy plants. Analysis of similarities (ANOSIM) and non-metric multidimensional scaling (NMDS) of the leaf volatile organic compounds (VOCs) showed that five terpenes, 2-δ-carene (25), β-phellandrene (29), δ- caryophyllene (13), elemene (58), and α- humulene (66) contributed to the dissimilarity trends between healthy and infected tomato irrespective of the nematode species. In further bioassays, the monoterpenes β-pinene (24), 2-δ-carene (25), α-phellandrene (26), and β-phellandrene (29) differentially attracted (51-87%) J2 relative to control. Concurrent reduction and increase in the levels of methyl salicylate (3) and (Z)-methyl dihydrojasmonate (45), respectively, in the root volatiles reduced J2 responses. Screenhouse pot experiments combined with laboratory in vitro hatching and mortality assays and chemical analysis to test the effect of non-host plant in growth and development of RKNs in susceptible host plants were used. In intercrop and drip pot experiments, blackjack significantly reduced the number of galls and egg masses in RKN- susceptible host plants by 3-9-fold compared to controls (susceptible plants). LC-QQQ-MS analysis of the most bioactive fraction from the root exudates of blackjack identified several classes of compounds, including aromatic acids, a dicarboxylic acid, vitamins, amino acids, and a flavonoid. In in vitro assays, the vitamins, ascorbic acid (86) and nicotinic acid (88) and the aromatic acids, p-coumaric acid (92) and 2-hydroxybenzoic acid (13) caused the highest inhibition in egg hatching, whereas ascorbic acid (86) (vitamin) and 2-hydroxybenzoic acid (13) (aromatic acid) elicited strong nematicidal activity against M. incognita, with LC50/48 h values of 12 and 300 ng µl-1, respectively. These results demonstrate that RKN infection induces chemical changes both locally and systemically in the host plant. Additionally, the host plant can alter its root volatile composition to inhibit PPN attack. The observed plant-produced inhibition of J2 warrants further investigation as a potential management tool for growers. The findings also provide insights into how certain non-host plants can be used as companion crops to disrupt PPN infestation.
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    Effect of Selected Bacterial Biocementation, Biodeterioration, Bioremediation on Selected Properties and Microstructure of Hydrated Cement Mortar
    (Kenyatta University, 2023) Ngari, Reginah Wangui; Joseph Karanja wa- Thiong'o; Jackson Wachira Muthengia
    Cement-made structures encounter durability and sustainability challenges. This is due to degradation by aggressive agents such as Cl-, SO42- and CO2. The presence of micro-organisms, such as Sulphur reducing bacteria (SRB) and Sulphur oxidizing bacteria (SOB), have been found to lead to production of cement degrading agents. On the contrary, there are micro-organisms that may benefit the mortar. Bacteria, for example that precipitate CaCO3, have found use in improving the performance or remediation of degraded concrete / mortar. In this study, the effect of Bacillus flexus, Bacillus cohnii and Thiobacillus thioparus on selected physico-chemical, mechanical properties and bioremediation of mortars was investigated. Growth of bacteria was done in a laboratory set-up. Bacteria concentration of 1.0 x 107 cells per mL of mix media was used. Mortar prisms were prepared using distilled water or bacteria solution as mix water and cured diistilled water or in bacteria solution. Control experiments had mortar prisms prepared using distilled water as mix and curing water. Pastes for setting time and soundness tests were similarly prepared using the above mix waters. Compressive strength, soundness, water absorption, setting time tests analyses were carried out for each category of mortars. Compressive strength test analyses were carried out on the 2nd, 7th, 14th, 28th, 56th and 90th day of curing of the mortars. Microstructural analyses of the hydrated mortars were conducted using Scanning Electron Microscopy (SEM). 28-day cured control and microbial mortars were subjected to water absorption analyses, chloride and sulphate ion ingress tests. From the results, the incorporated bacteria did not affect the soundness of cement significantly though setting time was significantly affected. Compressive strength was observed to increase with curing period for the Bacillus flexus and Bacillus cohnii with the highest gain observed at 90 days as 31.60 % for w/c of 0.4. On the contrary, there was a significant decline in compressive strength for all mortar where Thiobacillus thioparus was incorporated across all the curing regimes. The lowest percentage loss was observed as 44.38 % at 90 days for w/c of 0.6. Diffusivity of Cl- ions was highest for mortars subjected to Thiobacillus thioparus and lowest for Bacillus flexus. The same mortars exhibited Dapp of 2.5479 x 10-10 m2/s and 3.2977 x 10-10 m2 /s respectively. Dapp for SO42- showed a similar trend as Cl- ion. From the SEM images, microstructural analysis indicated presences of calcite (CaCO3), calcium silicate hydrate (CSH), ettringite, portlandite (Calcium hydroxide, CH) with the microbial mortars. A denser and a more refined microstructure with Bacillus flexus and Bacillus cohnii was observed as opposed to massive presence of voids, micro cracks and pores with Thiobacillus thioparus mortars. Generally, Bacillus flexus was a better CaCO3 precipitating bacteria than Bacillus cohnii. The results show that MICP was an effective method of remediating mortar that has been degraded by bacteria.
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    Synthesis of Super Absorbent Hydrogels Derived from Cross-Linking Activated Charcoal and Citric Acid for Sustainable Agriculture in Semi-Arid Regions
    (Kenyatta University, 2022) Kasimu, Titus Munyao; Harun M Mbuvi; Francis M Maingi
    Superabsorbent hydrogels represent a set of polymeric materials with three-dimensional structure. They are capable of holding huge amounts of water and due to the hydrophilic nature in the structure. Their applications in industries and environment are of prime importance. Currently application of polyacrylic and polyacrylamide super absorbers hydrogel in irrigation farming has been reported in western countries making farming economically viable. However, these hydrogels are non-biodegradable, toxic and expensive. Therefore, the pursuit of cheap and biodegradable hydrogels is desirable. Hence this study reports the synthesis and characterization of super absorbent hydrogels derived from activated charcoal (AC) and citric acid from lemon juice (LJ) which are locally available. This involved crosslinking activated charcoal (AC) and lemon juice (LJ) with ethylenediamine (EDA) or glycerol (G) in the absence and presence of maleic acid as a cross linker. Effects of hydrogels dosage on growth and yield parameters were investigated on DH 02 maize crop grown in semi- arid region of Mwala Machakos County during the April - July 2020 rains. Characterization of the hydrogels was done using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). The synthesis conditions that produced optimal swelling conditions were determined by varying contact time and dosage of activated carbon, lemon juice and maleic acid respectively. The FT-IR results showed absorption peaks at 1591.34, 1079.83, 1590.99, 1639.48 cm-1 for crosslinked superabsorbent hydrogel of Citric acid Glycerol (HLG-2), Citric acid Ethylenediamine (HLE-2), Activated carbon Ethylenediamine (HCE-2) and Activated carbon Glycerol (HCG-2). The peaks were associated with –COO- stretching vibration, -COO- strong symmetric stretching, C-N- stretching vibration, and -COO- bending in non-conjugated ester respectively which were a proof of successful ester crosslink upon addition of maleic acid during the synthesis process. XRD analysis showed that upon crosslinking the phase polymer network changed from amorphous to crystalline form. SEM analysis showed clear pores with large surface area in cross linked hydrogels compared with rigid and constricted surface of uncross linked hydrogels. Superabsorbent hydrogels for maximum swelling capacity were prepared using the following ratios. Swelling capacity of hydrogels prepared at optimum conditions of volume ratio CA: G: MA (5.4: 3.75: 3.75) HLG-2, CA: EDA: MA (144: 90: 75) HLE-2 while a mass ratio of AC: G: MA (6: 5:1) HCG-2 and AC: EA: MA (6:5:2) HCE-2 show that activated carbon functionalized with glycerol and cross linked with maleic acid has higher swelling percentage of 1255.80±0.70 % when subjected to a contact time of 12 hours. The application of 60 kg/ha of Activated carbon Glycerol showed highest mean growth and yield parameters compared to other superabsorbent hydrogels. This indicates that the prepared hydrogels have potential of reducing moisture stress in maize crops grown in semi-arid region. Super absorbent hydrogels synthesized from Activated charcoal and citric acid have potential application in agriculture owing to their high swelling capacities.
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    Microbial Effects on Physico-Mechanical and Microstructural Properties of Commercial Portland Cements
    (Kenyatta university, 2022-07) Munyao, Onesmus Mulwa; Joseph Karanja wa-Thiong’o; Jackson Wachira Muthengia
    Structures made using cement are prone to deterioration over time. Majority of structural failures have been attributed to inappropriate concrete mix designs, poor engineering designs, substandard aggregates, mixing water and sand. While many studies have focused on use of alternative cementitious materials to improve on the durability of existing Ordinary Portland cement (OPC), little attention has been given to microbial influence on concrete durability. This study investigated the influence of Thiobacillus intermedius, Starkeya novella and Acidithiobacillus thiooxidans bacteria on physico-mechanical and microstructural properties of selected Kenyan made cements. Commercial Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC) were used to cast the mortar prisms. The control mortar prisms were prepared using distilled water whereas the bacteria solutions were utilized as mix water, curing medium or a combination of two. The test cements were further subjected to 1.5 % sulphuric acid solution as a curing media. Physical characterization of both control and bacterial test cement pastes was carried out to determine normal consistency, setting time and soundness. Compressive strength was determined at 2nd, 7th, 28th, 56th and 90th day of curing. XRD and FTIR were used to characterize the hydration products of the test mortars after curing for 28 days. Scanning Electron Microscopy (SEM) was carried out to study the surface morphology of the hydrated cement mortars after curing for 28 days. Both control and bacterial mortar prisms were subjected to accelerated chloride and sulphate ingress test after curing for 28 days. Apparent Diffusion Coefficients (Dapp) were estimated from the solutions to Fick’s Second Law of Diffusion. Results showed conformity of physical characteristics of control and microbial cement pastes to Kenya cement standards. The compressive strength however decreased significantly for all the bacterial prepared mortar prisms. OPC exhibited the highest strength decrease of 33.5% at 90th day of curing when mixed and cured in Starkeya novella bacteria solution. SEM analysis showed extreme erosion of hydration products with formation of deleterious expansive ettringite crystals for the bacterial prepared mortars in the pore matrices. Control mortar prisms exhibited systematic formation of hydration products within the pore system. Mortars prepared with bacteria solutions as mixing water exhibited pronounced ingress of chloride and sulphate ions. OPC SK-SK mortars exhibited chloride and sulphate apparent diffusion coefficients (Dapp) of 8.2995 x 10-10 m2/s and 1.3562 x 10-9 m2/s respectively. There was increased water absorptivity in the microbial mortars. OPC SK-SK registered the highest water absorptivity of 72.75%. The exposed mortar prisms in 1.5% sulphuric acid solution exhibited low compressive strength at all curing ages with OPC demonstrating the highest decrease in compressive strength of 73.56% at 90th day of curing. Results from this study show that the selected bacteria commonly present in sewer systems play a vital role in deteriorating cement- based materials. This reduces the service life and the durability of the exposed cement structures with time. The work recommends development of remedial methods to prevent the bacteria attack on concrete and mortar structures placed in sewer and other aggressive environments.
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    Synthesis and Spectrophotometric Activity of Phthalocyanine Conjugated to Metal Nanoparticles and Evaluation of their Antibacterial Properties
    (Kenyatta University, 2021) Nyamu, N. Samuel; Eric Masika; Margaret Ng‘ang‘a; Lucy Ombaka
    In recent times, microbial pathogens have increasingly shown multi-drug resistance leading to a growing concern. Analysis of 624 isolates from Kenya revealed 88% of isolates tested were multi-drug resistant. It is estimated that about 4,150,000 deaths will be attributed to antimicrobial resistance (AMR) in Africa by 2050. Therefore, current research is increasingly focusing on antimicrobial photodynamic therapy that utilizes non-toxic photosensitizer exhibiting visible light activity towards the generation of free radicals and singlet oxygen which kill pathogens. The photo-sensitizer may be conjugated to visible-light responsive nanoparticles to further increase their photochemical activities. Phthalocyanine (Pc) is one of the promising dyes that have shown notable photochemical stability, a high degree of aromaticity and ease of structural modification resulting in increased activities. Despite these attractive properties, its antibacterial properties remain under researched. Therefore, this study aimed to tuning the photodynamic antibacterial activity of Pc by using electron withdrawing and electron donating group, conjugating the obtained compounds to silver nanoparticles (AgNps) and zinc oxide nanoparticles (ZnO-Nps) and evaluating the activity of the resulting composites against drug resistant strains Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Salmonella typhi. 2,9,16,23-tetra-iodo- 3,10,17,24-tetra-(3-methoxyprop-1-nyl) Pc (6) and 2,9,16,23-tetra-iodo-3,10,17,24-tetra ethylsulfonyl Pc (10) were synthesized respectively. The Pc derivatives were synthesized upon exposure to microwave radiation under solvent-free conditions. Both Pc 6 and 10 were β-form in nature with monoclinic structure confirmed by powder XRD. Pc (6) had two absorption bands between 345-364 nm for B-band and 660-680 nm for Q-band while Pc (10) indicated two major absorption bands between 354-360 nm for B-band and 685- 689 nm bands for Q-band of UV-Vis absorption in different solvents. FTIR confirmed the presence of attached substituent groups to the Pcs. Pc 6 and 10 showed singlet oxygen quantum yield (ΦΔ) values of 0.53 and 0.63 and fluorescence quantum yield (ΦF) value of 0.14 and 0.13 respectively. The Pc 10 exhibited zone of inhibition >23±0.12 μg/ml for all the strains, making it more effective as compared to Pc 6. In addition, all strains of tested bacteria were susceptible to Pc 10 at a concentration > 31.25 μg/ml. This implies that substituting Pc with electron withdrawing allows it to release more singlet oxygen in presence of light and which results to oxidation of the bacterial wall. AgNp and ZnO-Np were synthesized by microwave assisted extraction. The UV-Vis was used to confirm the formation of nanoparticles and also characterization done using FTIR, TEM and SEM. AgNps were of diameters ˂ 58.5 nm that easily conjugated to Pc while ZnO-Nps were of large grain size ˃ 95, the particles aggregated making it difficult to conjugate with Pcs. Conjugation of Pc 10 with AgNp ˂ 10 nm resulted to a more superior antibacterial as compared to unconjugated Pc 10. There was no significant different for zone of inhibition for Pc 10 conjugated to AgNp when compared to positive control ciprofloxacin at 500 μg/ml for all the strains except for B. subtilis. It had minimum inhibitory concentration (MIC) values of 3.91, 1.96, 1.96 and 15.63 μg/ml, for E. coli, S aureus, B. subtilis and S. typhi respectively. Both Pc showed no toxicity on Vero cells at concentration of 600 μg/ml. In overall, this work reports the successful tuning of the photo-chemical and antibacterial photodynamic properties of Pc using electron withdrawing and donating substituent. The Pc 10 with electron withdrawing group exhibit superior antibacterial activity which is further enhanced by conjugation with AgNp of ˂ 10 nm.
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    Simulated Bioaccessibility Studies of Beta-Carotene and Vitamin B Series in Selected Leafy African Indigenous Vegetables in Kisii County, Kenya
    (Kenyatta University, 2021) Moraa, Onyambu Zipporah; Mildred P. Nawiri; Hudson Nyambaka
    Over two billion people worldwide are affected by various vitamin deficiencies resulting in poor health, low gross domestic product and high mortality rates. Deficiency of vitamins remain a public health problem in the developing countries affecting mostly expectant and lactating mothers as well as children under five years of age. Despite a number of approaches taken in managing these deficiencies, the nutritional approach is still most preferred and especially employing leafy African indigenous vegetables (LAIVs), which can be consumed either fresh or processed. In Kenya, LAIVs are locally available and inexpensive. Although they are good sources of vitamins and other nutrients, the LAIVs are underutilized and face postharvest losses in seasons of high availability. Sun drying and oven drying are among the methods employed to address postharvest losses. The research gap presented is on the in vitro bioaccessibility of beta-carotene (BC) and vitamin B series to support promotion of LAIVs when consumed as individual fresh, processed or as recipes of mixtures and formulations, among the forms in which they can be consumed. This would inform on the amount of the same nutrients that are potentially available for absorption in the gastrointestinal tract once ingested. In vitro methods are preferred for being accurate, reproducible and have no ethical constrains among others. The general objective was to investigate the bioaccessibility of beta-carotene (BC) and vitamin B series in LAIVs, recipes and formulations using an in vitro method. Levels of vitamins were determined in the fresh and processed LAIVs; Cleome gynandra, Vigna unguiculata, Amaranthus viridis, Basella alba and Cucurbita maxima by UV-Vis spectrophotometry for BC and high performance liquid chromatography (HPLC) for vitamin B series. Gastrointestinal digestion was performed for the gastric and intestinal phases. The data obtained was analyzed by SPSS employing ANOVA to compare the mean levels and percentage bioaccessibilities of the vitamins. The mean (n=3) levels (mg/100g DW) of BC and the vitamin B series were sufficient to meet the recommended dietary allowances (RDAs) and provided the mean range of % bioaccessibility of BC of 61.36±1.87 to 97.23±0.06 (fresh), 65.67±5.53 to 84.31±0.27 (boiled) and 16.97±0.02 to 48.19±0.82 (boiled-fried) and for vitamin B ranged from 5.17±0.93 to 100.00±0.01 (fresh), 5.18±0.87 to 100.00±0.01 (boiled) and 14.23±3.69 to 100.00±0.01 (boiled-fried). In recipes the range of the mean % bioaccessibility of BC was 69.09±1.29 to 88.97±0.22 (RCP1) and 17.45±6.47 to 25.30±1.05 (RCP2) while that of vitamin B was 19.97±3.57 to 100.00±0.00 (RCP1) and 5.57±1.18 to 92.57±0.62 (RCP2). In formulations the range of the mean % bioaccessibility of BC ranged from 48.28±3.66 to 70.45±0.78 while that of vitamin B was 6.28±0.21 to 97.20±2.01. Statistical differences (p<0.05) were observed between processes, recipes and formulations. Both the fresh and processed vegetables were found to contain levels of BC and vitamin B series that meet the RDAs as set by the World Health Organization (WHO). The findings show there is sufficient in vitro bioaccessible levels of BC and vitamin B series with processing of LAIVs therefore promoting their consumption would play a significant role in addressing malnutrition and food security.
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    Microwave Synthesis of Super-Absorbent Hydrogels from Rice Husks Cellulose for Sustainable Agriculture
    (Kenyatta University, 2021) Abdulhameed, Adamu; Harun Mbatha Mbuvi; Evans Changamu Ogwagwa
    The phenomenon of climate change coupled with increased demand for water all over the world calls for innovations in water conservation and use. Moreover, rainfall variability and the corresponding implications are expected to continue worsening owing to the anticipated effect of global warming. Currently, inadequate water is considered as the key factor affecting crop growth and productivity in arid and semi-arid regions of Africa. Hence, there is need to explore and develop innovative ways to reserve and conserve water and nutrients and reduce moisture stress in food crops during mid-season drought. The use of superabsorbent hydrogels in crop growing as a means of ensuring sustained water supply to growing of plants has shown promising results. The superabsorbent hydrogels are capable of absorbing and retaining high amounts of water and releasing it under appropriate conditions. However, majority of the superabsorbent hydrogels are known to be expensive, non-degradable and environmentally unfriendly and are therefore unsuitable for use in agriculture. Hence, there is need for the development and optimization of non-toxic and environmentally friendly alternatives for use in agriculture. The objective of this study was to synthesize and characterize cellulose-based superabsorbent hydrogels from rice husks (Oryza sativa) cellulose under microwave heating and to evaluate their efficacy in the growing of maize in a green house. The cellulose used in this study was extracted from rice husks using acetic acid-nitric acid mixture. Some of the extracted cellulose was modified to carboxymethylcellulose by alkalization followed by reaction with monochloroacetic acid (MCA) under microwave heating. One half of the carboxymethylcellulose obtained was cross-linked using ethane-1,2-diol and the other with ethane-1,2-diamine, under microwave heating to form two different hydrogels. The unmodified cellulose was converted to hydrogels by crosslinking with phosphoric and boric acid, respectively. Separately, optimum synthesis conditions, that is, microwave power out-put, time (minutes), and amount of cross-linkers required were determined by measuring the percentage swelling of the hydrogels produced under different synthesis conditions in water. All hydrogels produced were characterized by Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The ethane-1,2-diamine superabsorbent hydrogel from carboxymethylcellulose showed the highest percentage swelling of 1175 %. The efficacy of the hydrogels in maize growing was determined by planting maize in pots in a greenhouse under different hydrogels and varied hydrogel dose treatments and measuring growth parameters over a period of twelve weeks. Yield parameters were determined at harvesting after 12 weeks allowing for complete drying. The values of plant growth and yield parameters were found to increase with hydrogel dose with the best results being observed among maize plants grown under the hydrogel dose of 5 g per pot for all the superabsorbent hydrogels. It was observed that the maize plants in pots without any hydrogel dried off without any yield as expected when rains fail. These results are significant in that they demonstrate that rice husks cellulose-based hydrogels are efficacious in maize growing in a greenhouse. Furthermore, the use of the agricultural waste, rice husks as a source of the cellulose means the rice husks now becomes a resource rather than an agricultural waste.
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    Mycotoxin Levels in Chicken Feeds and Products and Effects of Exposing Associated Fungi to Selected Plant Essential Oils in Kenya
    (Kenyatta University, 2020) Mueni, Githinji Irene; Margaret Mwihaki Ng’ang’a; Ethel O. Monda; Ahmed Hassanali
    Mycotoxins are secondary metabolites produced by fungi. The most toxic mycotoxins are particular secondary metabolites of Penicillium, Aspergillus and Fusarium fungi species that infect a variety of human food and animal feeds. Poultry farming has become one of the most profitable businesses in Kenya because of the growing demand of chicken and their eggs by households, hotels and restaurants. Besides creating employment, poultry meat and eggs are an alternative source of proteins for many people in both urban and rural areas. However, there is increased risk that poultry feeds may contain potential microbiological and toxicological contaminants that may compromise their safety and nutritional value. This study sought to quantify the levels of ochratoxin A (OTA), fumonisin B1 (FB1) and aflatoxin B1 (AFB1) in poultry feeds and chicken products using the Liquid chromatography-mass spectrometry technique, and to screen essential oils of selected ethnobotanical plants, individually and in different blends as potential inhibitors of fungi produced by Fusarium and Aspergillus species. Chicken feeds and chicken products were sampled from different agro-ecological zones in Kenya, where poultry farming is widely practiced. From the sampled chicken products and poultry feeds, 13.3 % and 46.9 % respectively were found to be OTA contaminated. All the poultry feed samples were found to be FB1 contaminated, while all the chicken products showed no detectable FB1 levels. AFB1 contamination occurred in 43.3% and 59.3 % of the sampled chicken products and poultry feeds, respectively. Contamination levels of OTA, AFB1 and FB1 differed significantly within the study regions and in different chicken feeds and products. Chicken feed and products from Kakamega County had the highest levels of OTA and AFB1 contamination. The mean levels of OTA in samples from Kakamega were 165.33±0.42 and 7.12±1.25 ng/g for chicken feeds and chicken products respectively. Kakamega had average levels of AFB1 of 32.44±1.54 ng/g in chicken feed and 4.10±1.33 ng/g in chicken products. Makueni County had the highest level of FB1 contamination in chicken feed (27700.00 ng/g). FB1 was not detected in all the chicken products. The mycelial diameter of A. niger, A. flavus and F. verticillioides decreased with increase in the concentration of each of the three plant essential oils, Lippia javanica, Ocimum gratissimum and Toddalia asiatica, from 1 μL/mL to 32 μL/mL. Essential oil of T. asiatica were most effective, followed by that of O. gratissimum, and lastly that of L. javanica. Of the blends of two essential oils, that of O. gratissimum and T. asiatica resulted in the least mycelia diameter, thus the best inhibitory activity against the growth of A. niger, A. flavus and F. verticillioides. On the other hand, the blend of O. gratissimum and L. javanica showed the least inhibition activity. A blend of all the three essential oils gave the highest growth inhibitory activity against the fungi, showing synergistic effects of various constituents of the three oils. Thus, this blend of L. javanica, O. gratissimum and T. asiatica at 32 μL/mL shows potential for use in the preparation of an efficient fungi inhibitor. Essential oils of L. javanica, O. gratissimum and T. asiatica contain phytochemicals that can be explored for mycotoxin causing fungi growth inhibition. However, further studies on the duration of efficacy, its toxicity, and constituents associated with the synergistc effect needs to be carried out.
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    Diammonium Phosphate Fertilizer from Bone–Phosphate Enriched Phosphoric Acid and Ammonia from Lithium Nitride and its Efficacy in Tomato Growing
    (Kenyatta University, 2021) Makhanu, Mutenyo Maxmilla; Evans Changamu Ogwagwa; Dickson Andala
    obtained from finite rock phosphate is one of the essential elements for food production and modern agriculture. Therefore, for sustainability of food supply and development in agriculture, management of phosphorus is key. The estimated periods within which the finite rocks might be depleted range from 30 to 300 years. There is a general agreement that there is a decrease in accessible reserves of phosphorus. Among the alternatives to rock phosphorus are animal bones disposed as waste from abattoirs in large cities and towns. Animal bones have a high concentration of phosphate that can be harvested and used in fertilizer production but they take many years to decompose and release the phosphate. The objective of this was to prepare bone-phosphate enriched phosphoric acid from discarded animal bones and use it to prepare DAP fertilizer and determine its efficacy in tomato growing in a greenhouse. Animal bones (predominantly cattle bones) were collected from Kachok Municipal dump site, Kisumu West District, Kenya. They were washed, dried and crashed to smaller particles using a hammer after which they were ground in a mill. The ground bones were extracted with 0.275M H3PO4 to give a 4.58 M bone phosphate-enriched phosphoric acid solution. Nitrogen was extracted from air by passing the air over heated copper filings and reacted with lithium to form lithium nitride. The lithium nitride was later hydrolysed to form ammonia which was reacted with the bone-phosphate enriched phosphoric acid to generate the diammonium phosphate (NH4)2HPO4) fertilizer. Lithum metal was recycled by electrolysis of LiCl using electricity generated by a hybrid solar – wind system in a cell fabricated at Kenyatta University‟s Engineering Workshop. The percent composition of nitrogen (Kjeldahl) in the diammonium phosphate was found to be 17.14 % N while that of the phosphate was found to be 44.58 % P2O5. The process realized 98.87 % N2 separation from air, 94.74 % lithium conversion to lithium nitride and 94.75% lithium nitride conversion to ammonia. The percentage yield of (NH4)2HPO4) obtained from the reaction of ammonia with 4.58 M H3PO4 was 48.06 %. The efficacy of diammonium phosphate in the growing of tomatoes in a greenhouse was determined with the commercially obtained diammonium phosphate as the positive control and no fertilizer as the negative control. Growth parameters of the tomatoes including plant heights, leaf length, leaf width and root length were obtained over a period of twelve weeks. The results showed that the growth parameters recorded for tomato plants grown with synthesized fertilizer were not significantly different from those recorded for tomato plants grown with commercial fertilizer (p-values = 0.000 <0.05). However, growth parameters of tomato plants grown without any fertilizer were significantly different (lower in value) from those grown with fertilizer. Based on the results obtained, it can be concluded that the bone phosphate based fertilizer prepared in this study was as efficacious as the commercial fertilizer.this is a significant finding in that it shows that it shows that animal bones can be converted into readily available phosphatic fertilizer. A pilot study on production of the same is recommended
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    Synthesis, Characterization, Bioassay and Density Functional Theory Studies of Cationic Iron Half Sandwich Complexes of Selected Heterofunctional Active Pharmaceutical Agents
    (Kenyatta University, 2020-02) Chengo, Katana
    The molecular modification of purely organic drugs by the incorporation of a metal atom is an active area of research. However, there is paucity of data in the use of half sandwich organometallic fragments and in particular the cationic iron half sandwich, [ɳ5-C5H5(CO)2Fe]+, in structural modification of drug molecules. The cationic iron half sandwich organometallic fragment provides a metal centre that could participate in biochemical reactions with potentially the desirable benefit of conferring new or modified modes of action of the drug molecules. Therefore, the objective of this study was to modify the molecular structures of the active pharmaceutical agents (APAs); 3-aminosalicylic acid (3-ASA), 4-aminosalicylic acid (4-ASA), 5-aminosalicylic acid (5-ASA), terizidone (TZD), ethionamide (ETH), prothionamide (PTH) and linezolid (LZD) by the incorporation of the cationic iron half sandwich organometallic fragment. A two pronged approach involving molecular modelling and organometallic synthesis was employed. In molecular modelling, the molecular geometries of the seven selected drug molecules were optimized and their local and global reactivity indices calculated in order to predict their ligation behaviours towards the iron half sandwich. The most stable molecular geometries and spectroscopic properties of the seven active pharmaceutical agents and their organometallic complex salts were predicted computationally using the DFT functionals; B3LYP, CAM-B3LYP and PBEPBE and 6-311g(d,p), 6-311g(2d,p) and LANL2DZ basis sets in Gaussian 09 and 16. Experimentally, the iron half sandwich organometallic salts of the APAs were synthesized, purified and characterized by FT-IR spectroscopy, 1H and 13C NMR spectroscopy, and elemental analysis. Antibacterial susceptibility tests of the new compounds against selected gram-positive and gram-negative bacteria showed that the LZD and TZD complexes had good abilities to inhibit the growth of the tested bacteria with comparable or better growth inhibition ability than their corresponding free ligands. Furthermore, the incorporation of the cationic iron half sandwich organometallic moiety to 3-ASA, 4-ASA, 5-ASA, ETH and PTH conferred antibacterial activity against the selected bacterial strains hence broadening the drugs spectra of activity. Therefore, the structural modification of APAs by the incorporation of the iron half sandwich can be pursued as a means of enhancing the usefulness of drugs.
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    Synthesis of (R)-1-Methyl-4-(1-Methylethenyl) Cyclohexene Multifunctional Derivatives and their Effects on Jatropha Curcas and Algae Biofuel Blends
    (Kenyatta University, 2020-10) Kahindo, John M.
    There is a growing increase in biofuel consumption around the world. Currently there is a desire to enhance biodiesel and biodiesel blends properties by use of multifunctional additives. This project sought to evaluate the miscibility of fatty acid ethyl ester blends from algae and Jatropha curcas L. oils and also synthesise hydrogenated and oxygenated derivatives of d-limonene as potential additives. Sampling of citrus peels was done from Milly Fruit Processors and Kongowea Mombasa. Algae were from Shimoni in Kwale, Shelly beach Mombasa, Jamvi la Wageni Mtongwe Likoni, English point Mombasa. J. curcas seeds were from contracted farmers in Shimba hills, Kwale County. Extraction of citrus oil containing d-limonene was done by use of hexane and liquid / Sc CO2. Catalytic synthesis of hydrogenated and oxygenated limonene derivatives was done using palladium on alumina Pd/Al2O3 and palladium on hydrotalcite Pd/HT respectively. Algae and jatropha seeds were dried, blended and extracted using hexane. The algae and citrus biomass were saccharified then fermented to obtain bioethanol.The algae and jatropha oils were transesterified using bioethanol, blended to form JAB then 2 – 10 % limonene and derivatives added to 20% JAB to form JABLA. GC-MS and FTIR spectrophotometers were used for characterisation. Determination of physicochemical and fuel properties was done using standard methods. Antimicrobial assay of JAB20 and JABLA was done using paper disc diffusion method. The properties of JAB and JABLA were then compared with those of diesel fuel and standard B100 biodiesel. The yield of orange oil was 5.748±0.719 %w/w using hexane. Pd composition of Pd/Al2O3 and Pd/HT was confirmed using XRF spectrometry to be 5% and 4.74% respectively. Characterisation showed that the oxidation products were mainly endo- and exo-epoxides, dihydrocarveol, carveol and carvone and hydrogenated products p-menthene, cis-p-menthane, trans-p-menthane, (S)-1-methylene-4-(1-methylethyl)cyclohexane and (R)-1-methylene-4-(1-methylethyl)cyclohexane. Bioethanol from citrus biomass was 9.42±1.031 % v/w. Algae oil produced 57-62% FAEE and J. curcas oil 63-70% FAEE. Characterisation of the ethyl esters showed mainly dodecanoic acid, tetradecanoic acid, pentadecanoic acid and hexadecanoic acid ethyl esters from algae oil and hexadecanoic acid, octadecanoic acid and 9z-octadecenoic acid ethyl esters from jatropha oil. JAB 5-20% was miscible, physicochemical and fuel characteristics showed that there was significant effect on the J. curcas FAEE calorific value, kinematic viscosity, pour point and cloud point with p < 0.05. The 2-8 % d-limonene additive showed effect on properties of JAB20 density, calorific value, kinematic viscosity, flash point, cetane index, pour point and cloud point with p< 0.05 except for CFPP with a p = 0.215. For 2-8 % hydrogenated d-limonene additive showed effect on density, calorific value, kinematic viscosity, flash point, cetane index, pour point and cloud point p< 0.05. The 2-8 % oxygenated d-limonene additive had effect on density, cetane index and pour point p < 0.05 according to data obtained using STATA/SE 13.0 and Xlstat at 95% confidence level two -tailed. JABLA showed no significant difference in fuel properties with petroleum diesel and standard B100 biodiesel p=0.110. The 8% oxygenated d-limonene also showed Pseudomonas aeroginosa growth inhibition of 23.20 ± 0.80 mm and Candida albicans growth inhibition of 25.30± 0.30 mm. From the findings the additives have beneficial effect on physicochemical and fuel properties of J. curcas and R. grande biofuel blend for increased sustainability and longer shelf life hence potential additives to the biofuels.
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    Bioprospecting for Anti-Mosquito Phytochemicals Associated With Olfaction and Larvicidal Activities From Selected Kenyan Plants
    (Kenyatta University, 2020) Ochola, John Bwire
    Mosquitoes are of high public health concern since they are significant disease vectors of different tropical and subtropical life-threatening diseases like malaria, dengue, yellow fever, chikungunya, zika virus and encephalitis. Use of synthetic insecticides for control of mosquitoes causes development of resistance in vector species and have negative effects to the environment and human. This study aimed to find alternative, effective tools against these vectors from plant essential oils. Plant-based products are promising alternatives of lowtoxicity, eco-friendly and low-cost. Oils from air-dried aerial parts of Satureja biflora, Satureja abbysinica, Conyza newii and Plectranthus marrubioides from Aberdare and Ocimum kilimandscharicum from Kakamega in Kenya were extracted using Clevenger apparatus. Oil yields were determined and analyzed by Gas Chromatography/Mass Spectrometry. Repellency of the oils was assessed on adult mosquitoes in ‘WHO arm in the cage’ method, while 3rd instar larvae were used to assess larvicidal activities based on WHO protocol. Oil with better larvicidal activity was formulated into a water-miscible solution for laboratory and semi-field testing. GC linked to EAG detector was used to determine the constituents that elicited chemosensory responses from the antenna of An. gambiae. Individual constituent contribution to mosquito repellence was established through a subtractive-combination bioassay. From the results, oils from different habitats and seasons showed qualitative and quantitative differences. Thirty three (33) compounds were identified in S. biflora oil with 3 chemotypes based on location: geranial(31%)/neral (24%)/linalool (12%) of Kinale, linalool (28%)/neridol (21%)/β- pinene (7.4%) of Nyahururu, and geranial (27%) neridol (Z) (21%)/linalool (16%) of KieniGakoe. S. abyssinica had also 33 compounds comprising majorly menthone (44.1%) and pulegone (33.3%). C. newii had 19 components forming 2 chemotypes p-mentha-1,8-dien-7-yl acetate (24%)/limonene (23%)/5-methyl-2-phenyl-2-hexenal (21%) associated with Nyahururu, and p-mentha-1,8-dien-7-yl acetate (27%)/ limonene (38%). P. marruboides and O. kilimandscharicum had 35 and 41 components respectively. The major compounds in P. marrubioides were carene-2-δ (18.7%) and camphor (17.9%), whereas for O. kilimandscharicum was camphor (36.6%) and limonene (18.6%). C. newii (Nayahururu) S. biflora (Kieni) and S. biflora (Nyahururu) gave a high repellence of ED50 at < 1.95 ppm, whereas S. biflora (Kinale) had ED50 at < 2.35 ppm against Ae. aegyptei and An. gambiae. Besides, C. newii had strong repellence with ED50= 0.5 ppm against An. gambiae. Comparatively DEET gave the highest protection time of 389 min against An. gambiae, followed by C. newii (cream) against the 3 mosquito species; 241, 206 and 60 minutes for An. gambiae, Cx. quinquefasciatus and Ae. aegyptei respectively. S. biflora cream gave 208, 180 and 56 minutes against An. gambiae, Cx. quinquefasciatus and Ae. aegypti respectively. Addition of vanillin to the cream formulation resulted in a longer protection time of 382 min against An. gambiae. Nine EAG-active constituents were identified. Perillyl alcohol and α- pinene increased repellency, while neral, geraniol, perill aldehyde and cinnamaldehyde-α- pentyl reduced the repellency of the respective blends. Limonene and linalool interchangeably increased or decreased the repellence based on the resulting blend. O. kilimandscharicum oil showed the highest larvicidal effect against 4 mosquito species, with LD50 of 0.292 and 0.41ppm at 24 and 48 hrs respectively against An. gambiae larvae. The O. kilimandscharicum water miscible formulation recorded a LC50 of 0.13, 0.14, 0.16 and 0.13ppm against larvae of An. gambiae, Ae. aegypti, Cx. quinquefasciatus and An. arabiensis respectively. In a semi-field setup, the larvicidal formulation at 0.5ppm on day 8 attained 100% larval reduction when B.ti had 96.5%. The larvicidal and repellent results of the plant formulations generated in this study have demonstrated high potential for practical application in control of mosquito vector borne diseases and need to be deployed for large scale field trials and registered with the relevant bodies for adoption for control of mosquitoes.
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    Biomass-Based Fertilizer Formulation Using Chemically Decomposed Agricultural Wastes and Evaluation of Its Efficacy in Growing Maize
    (Kenyatta University, 2020) Echessa, A.C. Peter
    Utilization of the conventional fertilizers such as NPK, DAP, CAN and Urea by smallholder farmers in developing countries like Kenya has remained dismal due to high retail prices as well as environmental and soil related concerns such as P-fixation, leaching and volatilization. Organic fertilizers generated using traditional composting methods come in handy despite own challenges of long composting periods, imbalanced nutrients and environmental impacts of pathogens. The long composting period can be shortened through chemical decomposition of selected farm wastes that can provide balanced nutrients. The objective of this study was to utilize chemically decomposed agricultural wastes to formulate a biomass-based fertilizer and evaluate its efficacy in growing maize. Selected agricultural waste (maize cobs, maize stalks, sugar cane bagasse, sisal leaf pulp and cattle horns/hoofs) were analyzed for nutrients N, P, K and Ca to determine their suitability for formulating a Biomass-Based Fertilizer (BBF). Results indicated that the agricultural wastes had varied levels of macronutrients sufficient to support use in fertilizer formulation. The acidic sisal leaf pulp required basic conditions to decompose. The lye from burned maize cobs was used to digest sisal leaf pulp to give a basic cobs ash sisal digest (CASD) product while cattle horns and hoofs soaked in peracetic acid gave an acidic horns and hooves digest (HD) product. HD (acidic) was mixed with CASD (basic), (HD: CASB) in varying ratios to give different fertilizer formulations namely, BBF0 (0:1), BBF1 (1:1), BBF2 (2: 1), BBF3 (3:1), BBF4 (1:2) and BBF5 (1:0). The formulations had pH varying from 6.82±0.15 to 8.41±0.27 and would provide macronutrients in the ranges of 1.0-3.9 g (N), 0.002-0.17 g (P), 0.001-6.30 g (K) and 0.08-9.20 g (Ca) per plant environment. Fertilizer formulation BBF1, with pH above 7.5 and macronutrients 2.31% N, 0.08% P, 2.5% K and 3.46% Ca, was used in efficacy study carried out in Lugari, Kakamega county because of the acidic nature (pH<7.0) of the field soils. Plant height and yield of maize under the BBF1/BBF1 and that under the DAP/CAN schedules were comparable, but differed significantly from those of maize in the plots without fertilizer schedule. Side dressing maize whose leaves developed purple coloration (phosphorus deficiency) with freshly prepared BBF1 cleared P-deficiency symptoms in ≤ 7 days. Chemical decomposition of agricultural wastes produces digests that blend into a BBF formulation that is effective in promoting growth and yield of maize crops.
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    Structure-Activity Studies and On-Host Evaluation of Controlled-Release Formulations of Optimised Potent Repellents Against Rhipicephalus Appendiculatus
    (Kenyatta University, 2020-08) Kariuki, Margaret Wangechi
    East Coast Fever (ECF), commonly known as theileriosis, is a tick-borne disease caused by a protozoan organism known as Theileria parva. It has been a major limitation in livestock production and food security in several developing countries. ECF is transmitted predominantly by the brown ear tick, Rhipicephalus appendiculatus. In Africa, it is estimated that about 1.1 million cattle suffer from ECF resulting to losses of about US dollars 168 million. In Kenya, approximately 50-80% of the national cattle population of about 10 million animals is vulnerable to tick infestations, and out of this number, 1% die of ECF each year. Use of semiochemicals represents a prospective eco-friendly strategy for the control and management of the vector. Previously, on-host behavioral observations showed preference of R. appendiculatus adults to feed primarily inside and around the ear of their hosts. Combination of a repulsive blend from the anal region and an attractive blend at the ear was revealed to play natural “push” and “pull” roles, respectively, to guide the ticks to their predilection feeding sites. In a preliminary study, use of a crude repulsive blend obtained from the anal region at the ears was found to confuse the ticks, most of which dropped off the cattle. In a follow up study, 4-methylguaiacol was found to be the major component of cattle anal odour, and also most repellent to R. appendiculatus. Three sets of studies were then carried out. First, structure-activity of 10 analogues of 4-methylguaiacol and that of selected blends was performed at different doses in a dual-choice climbing assay set up. Each analogue showed either higher or lower repellency compared with 4-methylguaiacol. The structural feature that was associated with the highest repellency was 4-propyl moiety in the guaiacol unit (RD75 = 0.031 for 4-propylguaiacol; that of 4-methylguaiacol, RD75 = 0.564). However, blending selected analogues with high repellency showed no incremental increases in repellency compared with that of 4-propyl-2-methoxyphenol. Second, encapsulation of 4-propylguaiacol in β-cyclodextrin, ethyl cellulose and PVP, respectively, was carried out, and the inclusion of 4-propylguaiacol in the resulting complexes was confirmed by FT-IR, XRD and SEM. The rates and duration of release of the repellent from 0.2 g of each inclusion complex were then compared at 38-40 0C every 3 hours for 24 hrs. The β-cyclodextrin complex was found to last longer than the others with a release rate of 0.396 mg per hr. Third, on-host behavior effects of individual ticks (male or female) placed at one of six different body locations (i.e. forehead, shoulders, dewlap, escutcheon, hind leg and front leg) of Friesian steers, with no prior exposure to ticks, and tagged with β-cyclodextrin, ethyl cellulose or PVP inclusion complexes at one or both ears, were monitored. Tagging the treatment on one ear and both ears showed that β-cyclodextrin complex gave the best repellency with Mean ± SE of 0.64 ± 0.05 for tagging the treatment on one ear and Mean ± SE 0.35 ± 0.05 for tagging on both ears for ten days. Tagging the treatment on both ears gave 100% protection for seven days. This makes the complex a superior means of delivering the repellent and on-host use than the other complexes. The tagging on both ears was more effective than tagging on one ear. The most appropriate dosage was 0.5 mg with Mean ± SE 0.35 ± 0.05 when the treatment was on both ears. The β-cyclodextrin complex was found to repel the ticks for a longer time. This push approach exhibited by the β-cyclodextrin complex in small doses for a long time provides a potential tool to protect the cattle against the brown ear tick.
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    Optimization of Nutrients Release Parameters in Synthesized Hydrogel Minerals Anchored Material for Growth of Selected Plants in Embu County, Kenya
    (Kenyatta University, 2020-12) Kiriro, Grace Nduta
    Soil is the natural basis for plants growth as it not only provides support, water and minerals, but also helps to aerate the roots for proper development. However, due to the ever-growing population, available land is becoming a challenge. Urbanization also leads to insufficient surface for food production, as the arable land is used for settlement. This has further been exacerbated by erratic climatic conditions. Due to such limitations, this has compelled other options to be considered. Such options are growing of plants in soilless media that include hydroponic crop production and growing plants in sand, gravel or other liquids where the requisite nutrients are added. These methods allow a more efficient use of water and fertilizers, as well as better control of climate and pest factors. Despite the success in hydroponic production, there are challenges in that there is need for air circulation in the nutrient rich solution, plant support mechanism and disposal of the high concentrated nutrient solution into the environment after use putting a stress to the already stressed natural resource. Due to such limitations, there is a need therefore to come up with a method that will address such challenges. However, growth and propagation of plants for food crop can be made possible in soilless media if suitable conditions are provided. The objective of the study was to synthesize a solid phase nutrient anchored substrate material for growth of selected plants watered by hydrogels of bio origin. The substrate material was synthesized and then characterized using Fourier Transform Infra-Red (FTIR) and Nuclear Magnetic Resonance (NMR) to confirm the modification. Suitable minerals were then anchored by complexation in the substrate material and this was confirmed by X-ray Photoelectronic Spectroscopy (XPS). The release parameter and concentrations of the minerals was investigated using Differential Pulse Anodic Stripping Voltammetry (DPASV) and Flame Atomic Absorption Spectroscopy (FAAS) respectively. The substrate material was watered using hydrogels synthesized by modification of biomass. The modified biomaterials were characterized using Thermo Gravimetric Analysis (TGA), UV –Vis and FTIR spectroscopy. It was observed that mineral released increased with decrease in pH and at a pH value of 5.5, 90% of the nutrients were available for plant uptake. It was found that complexation of Fe2+ had a stability constant of 1.99×1014M-1. This implies that the non-biodegradable material has a potential application as a media for plants growth. The swelling ability of the hydrogels was investigated. It was found that the modified biomaterials had superabsorbent properties as the some had a capable of holding 30 times by mass content of water within 5 minutes of exposure. The plant growth media plus each respective hydrogels were then used for the growth of some selected plants (Spinacia oleracea L., Solanum tuberosam L. and Carica papaya). The modified biomaterials had a retention capacity of 90 % for the first 4 weeks of application. It was also observed that growth analysis using the leaf area index were higher on plants grown in 10 g plant growth substrate media watered by 50 g of the cellulose-urea and cow dung-urea gels which were found to have an average growth rate of 0.045/wk. This growth was made possible by adequate aeration provided by volume variations of the gel and support provided by the solid particles of the soilless media. The hydrogel watered substrate was done in potted plants as well as in artificial gardens to grow vegetables rich in nutrients and the findings extrapolated for growth of some selected plants in an arid area. Therefore the synthesized materials have a potential application for the growth of crops in arid areas.
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    Nutrition-Sensitive Intervention with Selected African Indigenous Leafy Vegetables Among School-Going Children in Machakos County, Kenya
    (Kenyatta University, 2020-11) Wakhanu, John Akello
    The 2014 Kenya Demographic Health Survey (KDHS) and Micronutrient Survey report showed malnutrition among children aged 5-11 years in Kenya. In particular, malnutrition in Machakos County manifested as stunting (26.3 %), wasting (6.3 %), underweight (12.7 %), marginal vitamin A deficiency (VAD) (33.9 %), anemia (16.5 %), zinc deficiency (82.5 %) and iron deficiency (9.4 %). African Indigenous Leafy Vegetables (AILVs) such as Vigna unguiculata and Amaranthus cruentus can be used to fight malnutrition in school-going children, based on their high micronutrient levels, but they need to be made more available to these children. The cultivation of AILVs as well as their consumption can be optimized through school garden establishments and the effect of the AILVs’ consumption on the children’s nutrition status accurately determined. This is to generate data to support the recommendation by 2014 KDHS that food based intervention through garden establishment can fight malnutrition. However, empirical data to support this recommendation employs determining body mass index, a limited technique as compared to deuterium dilution isotope (DDI) method that measures fat free mass (FFM) and fat mass (FM). The objective of the study was to determine the effect of consuming school garden-sourced vegetables on nutritional status of school children in Machakos County, Kenya. This was an experimental cross over design study with 4 weeks in between phases, phase I (13 weeks) and II (12 weeks). In phase I study subjects (children aged 6-10 years) who met the inclusion criteria were grouped as experimental (Kangundo, N=66) and control (Kilalani, N=46). The experimental group fed on a recipe of Vigna unguiculata and Amaranthus cruentus grown in school gardens of Kangundo and Kilalani primary, Machakos, with an accompaniment of a mixture of maize grains and beans once a day, 5 days a week per phase while the control group had only the accompaniment. The baseline information on dietary practices, morbidity, socio-demographic, economic factors and anthropometry of children were collected using a structured questionnaire. Hemoglobin (HB) was measured by a hemoglobinometer, while levels of Fe and Zn in raw and cooked recipe and in blood samples were determined using AAS procedure. The body FFM and FM was determined by DDI method and saliva analyzed by Fourier Transform Infrared (FTIR) spectroscopy, while serum retinol and BC were analyzed by HPLC. Baseline results showed poor consumption of indigenous vegetable (< 20 %), high morbidity (> 40 %), low socio-economic status of the parents/guardians (> 95.6 % who earned
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    Modified Bio-Sorbents for Pre-Concentration of Essential Trace Elements from Raw and Fermented Selected Foods
    (Kenyatta University, 2020-03) Tonui, Mathew Kipngetich
    This study reports a new method of pre-concentrating Zn2+, Fe2+, Mn2+, Mo6+ and I- ions present in food stuffs using modified bio-sorbents. These elements are in low levels in many food stuffs commonly consumed and some are way below the recommended daily intake (RDI). Examples of mitigating such situations include the addition of iodine to table salt in minute portions. However, table salt in foods increases sodium levels causing problems to consumers with high blood pressure. Dietary iron supplements have been used by people with iron deficiency in their bodies. Stomach upsets and pain, constipation, nausea and vomiting have been reported as some of the side effects of taking iron supplements. There is need therefore to find a way of increasing their levels in food intake. A possible route for this is to pre-concentrate these elements from common foodstuffs using readily available bio-sorbents. Maize cobs (Zea mays L.), common beans husks (Phaseolus vulgaris L.) and millet tassels (Eleusine coracana L.) which have traditionally been used either to make animal feeds or manure were used as pre-concentrating agents through adsorption. Another route is through fermentation followed by pre-concentration. The bio-sorbents were separately chemically modified and characterized to confirm the presence of the anchored functional groups using Fourier Transform Infrared (FT-IR) spectroscopy. Sorption capacities of essential trace elements by chemically modified and unmodified biomaterials were investigated separately using batch sorption experiments. Sorption parameters such as pH, concentration, contact time and dosage of both modified and unmodified forms of adsorbent were investigated. Essential trace elements present in black nightshade (Solanum nigrum L.) leaves, spinach (Spinacia oleracia L.) leaves and pumpkin (Cucurbita maxima L.) flesh aqueous extracts were determined without pre-concentration, after pre-concentration, and in fermented samples followed by pre-concentration. Best adsorption pH values ranged between 5.0 to 6.0 for Zn2+, 4.0 to 4.5 for Fe2+, 6.0 to 6.5 for Mn2+, 4.0 to 6.0 for Mo6+ and 5.0 to 5.5 for I-. The optimum concentration for all ions was found to be best below 50.0 mg/L while adsorption dose was best below 60.0 mg. The results show adsorption fitted more to the Langmuir model which had R2 values in the range 0.9957 to 0.9999 than Freundlich model with R2 values in the range 0.6710 to 0.9632 for all adsorbents. Sorption kinetics indicates pseudo second order model can be used to explain the rate determining step. The results show that fermentation increased the concentration of the essential trace elements in the solution. The elements were then pre-concentrated with pre-concentration ratios of up to 5.0 being achieved. The bio-sorbents are re-generable up to ten times. The results from this study have a potential application in the preparation of dietary supplements for human consumption. The study therefore recommends that this new method of preconcentration be adopted in large scale production of dietary supplements.
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    Facile Remediation of Fluoride in Aquatic Media Using Modified Polyethylene Container
    (Kenyatta University, 2020-07) Mbugua, Wachira Gerald
    Development of environmentally friendly and economically viable water treatmet techniques for remediation of fluoride ions in drinking water has gained a huge research interest. Floridated water is associated with dental and skeletal disorders. Previously used water treatment methods encountered several limitations such as operational problems and are not regeneratable. Adsorption technique is easy to use and is regeneratable. Adsorbents used include activated carbon and bone char. However, activated carbon is expensive while bone char is not acceptable to some religions. Therefore there is need to search for cheaper and widely acceptable adsorbents. This research studied the use of polyethylene wastes from the enivironment `as a green water treatment technique. Polyethylene wastes were separately dispersed in 1, 2-dichloroethane or liquid vegetable oil. The dispersed wastes were each divided into two where one portion was chemically modified with ethylamine, diethylamine and triethylamine separately. Both modified and unmodified adsorbents were characterized using fourier trasnsform infra red spectroscopy (FTIR), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The characterized materials were subjected to removal of fluoride ions and optimal parameters were applied. Liquid vegetable oil dispersed and activated with triethylamine adsorbent gave an adsorption capacity of 10.30 mg/g at pH 7. 0 fitting well in Langmuir model (R2 = 0.864) and was a pseudo first order (R2 = 0.726). When 1, 2 dicholoroethane dispersed and activated with triethylamine adsorbent was used, removal capacity of 0.17 mg/g at pH 4.0 was recorded. Using fabricated container, Lake Baringo water sample having a fluoride ion concentration of 2.5 mg/L had its fluoride concentration reduced to 1.5 mg/L. Thermodynamic parameter proved that fluoride ions removal was a spontaneous and exothermic process. This study presents an ecofriendly and cheaper method for water treatment and helps to curb polyethylene waste menace in the environment.
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    Bioprospecting for Anti-Mosquito Phytochemicals Associated with Olfaction and Larvicidal Activities from Selected Kenyan Plants
    (Kenyatta University, 2020-01) Ochola, John Bwire
    Mosquitoes are of high public health concern since they are significant disease vectors of different tropical and subtropical life-threatening diseases like malaria, dengue, yellow fever, chikungunya, zika virus and encephalitis. Use of synthetic insecticides for control of mosquitoes causes development of resistance in vector species and have negative effects to the environment and human. This study aimed to find alternative, effective tools against these vectors from plant essential oils. Plant-based products are promising alternatives of low-toxicity, eco-friendly and low-cost. Oils from air-dried aerial parts of Satureja biflora, Satureja abbysinica, Conyza newii and Plectranthus marrubioides from Aberdare and Ocimum kilimandscharicum from Kakamega in Kenya were extracted using Clevenger apparatus. Oil yields were determined and analyzed by Gas Chromatography/Mass Spectrometry. Repellency of the oils was assessed on adult mosquitoes in ‘WHO arm in the cage’ method, while 3rd instar larvae were used to assess larvicidal activities based on WHO protocol. Oil with better larvicidal activity was formulated into a water-miscible solution for laboratory and semi-field testing. GC linked to EAG detector was used to determine the constituents that elicited chemosensory responses from the antenna of An. gambiae. Individual constituent contribution to mosquito repellence was established through a subtractive-combination bioassay. From the results, oils from different habitats and seasons showed qualitative and quantitative differences. Thirty three (33) compounds were identified in S. biflora oil with 3 chemotypes based on location: geranial(31%)/neral (24%)/linalool (12%) of Kinale, linalool (28%)/neridol (21%)/β-pinene (7.4%) of Nyahururu, and geranial (27%) neridol (Z) (21%)/linalool (16%) of Kieni-Gakoe. S. abyssinica had also 33 compounds comprising majorly menthone (44.1%) and pulegone (33.3%). C. newii had 19 components forming 2 chemotypes p-mentha-1,8-dien-7-yl acetate (24%)/limonene (23%)/5-methyl-2-phenyl-2-hexenal (21%) associated with Nyahururu, and p-mentha-1,8-dien-7-yl acetate (27%)/ limonene (38%). P. marruboides and O. kilimandscharicum had 35 and 41 components respectively. The major compounds in P. marrubioides were carene-2-δ (18.7%) and camphor (17.9%), whereas for O. kilimandscharicum was camphor (36.6%) and limonene (18.6%). C. newii (Nayahururu) S. biflora (Kieni) and S. biflora (Nyahururu) gave a high repellence of ED50 at < 1.95 ppm, whereas S. biflora (Kinale) had ED50 at < 2.35 ppm against Ae. aegyptei and An. gambiae. Besides, C. newii had strong repellence with ED50= 0.5 ppm against An. gambiae. Comparatively DEET gave the highest protection time of 389 min against An. gambiae, followed by C. newii (cream) against the 3 mosquito species; 241, 206 and 60 minutes for An. gambiae, Cx. quinquefasciatus and Ae. aegyptei respectively . S. biflora cream gave 208, 180 and 56 minutes against An. gambiae, Cx. quinquefasciatus and Ae. aegypti respectively. Addition of vanillin to the cream formulation resulted in a longer protection time of 382 min against An. gambiae. Nine EAG-active constituents were identified. Perillyl alcohol and α-pinene increased repellency, while neral, geraniol, perill aldehyde and cinnamaldehyde-α-pentyl reduced the repellency of the respective blends. Limonene and linalool interchangeably increased or decreased the repellence based on the resulting blend. O. kilimandscharicum oil showed the highest larvicidal effect against 4 mosquito species, with LD50 of 0.292 and 0.41ppm at 24 and 48 hrs respectively against An. gambiae larvae. The O. kilimandscharicum water miscible formulation recorded a LC50 of 0.13, 0.14, 0.16 and 0.13ppm against larvae of An. gambiae, Ae. aegypti, Cx. quinquefasciatus and An. arabiensis respectively. In a semi-field setup, the larvicidal formulation at 0.5ppm on day 8 attained 100% larval reduction when B.ti had 96.5%. The larvicidal and repellent results of the plant formulations generated in this study have demonstrated high potential for practical application in control of mosquito vector borne diseases and need to be deployed for large scale field trials and registered with the relevant bodies for adoption for control of mosquitoes