Browsing by Author "Cheruiyot, Dennis Kipngenoh"

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    Isolation and Characterization of L-Asparaginase Producing Endophytic Fungi Inhabiting Prunus africana and Periploca linearifolia
    (Kenyatta University, 2025-09) Cheruiyot, Dennis Kipngenoh
    The clinical use of L-Asparaginase derived from bacterial sources has been hindered by various challenges, including toxicity and repression. This has prompted the exploration of alternative sources, particularly eukaryotic microorganisms like fungi, in an effort to enhance the safety and effectiveness of therapeutic ASNase. In this study, endophytic fungi isolated from medicinal plants, Periploca linearifolia (Apocynacease family) and Prunus africana (Rosaceae family), were investigated for their potential as a source of novel ASNase for therapeutic applications. These isolates were screened for L-Asparaginase production using the plate assay method on modified Czapex dots agar medium. L-Asparaginase activity of the fungal endophytes was determined using the nesslerization method. Identification of the fungal endophytes was performed using morphological characteristics and DNA barcoding with ITS sequencing, followed by BLAST analysis. Additionally, a phylogenetic tree was constructed using MEGA version X software. Twenty-four percent of the fungal endophytes exhibited positive reaction for L-ASNase activity and were identified as Penicillium ubiquetum, Penicillium pancosmium, Phoma sp, Penicillium. crustosum, Fusarium sporotrichioides, Cercospora canescens, Penicillium commune, septoria sp, Fusarium solani, and Colletotrichum sydowii. The fungal endophytes exhibited significant variation in production of L-asparaginase under the inflence of time of incubation and pH. It was observed that the fungal endophytes showed L-asparaginase activity at different day of incubation with Penicillium ubiquetum (2.63±0.47UI/mL), Penicillium pancosmium (1.44±0.1UI/mL), Phoma sp (2.6±0.47UI/mL), Penicillium crustosum (3.80±0.37 UI/mL), Penicillium commune (2.52±0.29 UI/mL), Fusarium sporotrichioides (3.47±0.24 UI/mL), Cercospora canescen (2.24±0.12 UI/mL) showed highest enzyme activity on the 6th day of incubation. Septoria sp and Colletotrichum sydowii exhibited best L-asparaginase activity of 12.6±0.81UI/mL and 4.06±0.23 UI/mL on the 9th day of incubation, respectively. While Fusarium solani showed atmost L-asparaginase activity of 12.4±1.12 UI/mL on the 12th day of incubation. In addition, the ten identified fungal endophytes records the highest activity at pH range 5.0-6.0 with Fusarium solani recording the highest enzyme activity of (6.14±0.01 UI/mL) at pH 6.0. The study revealed that fungal endophytes inhabiting plants with medicinal properties are potential source of L-Asparaginase. Among the fungal isolates, Fusarium solani and Septoria sp. showed the highest ASNase activity under optimized conditions (pH 5-6, incubation 9-12 days), indicating their potential as safer alternative to bacterial L-Asparaginase for anticancer therapy.
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    Optimization of Cellulase Production by Nigrospora Oryzae (Berk and Br.) Petch and Its Application in Biomass Saccharification and Ethanol Production
    (elsevier, 2026-01-10) Dukuzimana Olivier; Omwenga, George Isanda; Cheruiyot, Dennis Kipngenoh; Ngugi, Mathew Piero
    The increasing demand for sustainable biofuel alternatives has intensified the search for new microbial sources of cellulolytic enzymes. This study aim to evaluate the cellulolytic potential of Nigrospora oryzae and to optimize its cellulase enzyme production using low-cost lignocellulosic substrates, specifically maize cobs and sugarcane bagasse, under solid-state fermentation. Additionally, the study assess the efficiency of crude cellulase enzymes in biomass saccharification and bioethanol production. Molecular identification confirmed the isolate as N. oryzae through ITS sequencing and phylogenetic analysis. N. oryzae exhibited significant cellulolytic activity on carboxymethylcellulose-Congo red agar. Maize cobs and sugarcane bagasse were used as primary substrates for enzyme production. The cultural parameters were optimized using a one-variableat-a-time (OVAT) approach. The peak filter paperase (FPase) activity reached 11.3 ± 0.94 IU/ml for maize cobs and 8.9 ± 0.47 IU/ml for bagasse on day 9. Additionally, maximum endoglucanase activity was recorded at 19.7 ± 1.74 IU/ml and 15.5 ± 0.76 IU/ml on day 12, respectively. Exoglucanase activity peaked at 3.46 ± 0.25 IU/ml for maize cobs and 2.06 ± 0.11 IU/ml for bagasse. The optimal pH for enzyme secretion ranged from 5 to 6. Nitrogen supplementation with ammonium nitrate, urea, and peptone significantly enhanced enzyme yields. Among the carbon sources tested, fructose, mannitol, and sucrose markedly improved enzyme production compared to glucose, suggesting a partial relief from carbon catabolite repression. An enzyme loading of 5% optimized saccharification efficiency. Simultaneous saccharification and fermentation (SSF) using Saccharomyces cerevisiae achieved maximum ethanol concentrations at substrate levels between 5% and 15%, demonstrating the bio-conversion potential of this system. These findings position Nigrospora oryzae as a promising non-conventional cellulase producer for lignocellulosic bioconversion, with significant implications for sustainable ethanol production
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    Toxicity Evaluation, Phytochemical Characterization and Pharmacological Effects of Aqueous Extracts of Combretum Collinum Leaves: Analgesic, Antipyretic, and Anti-Inflammatory Activities in Animal Models
    (Scientific African, 2025-09) Kefa, Bunei Kipngetich; Chumba, Careen Ihazano; Gathuka, Daniel Kingori; Cheruiyot, Dennis Kipngenoh; Mwonjoria, John Kingori; Njagi, Eliud Nyaga Mwaniki
    The leaves of Combretum collinum are traditionally used to treat inflammation and promote wound healing. This study aims to assess the toxicity, phytochemical characterization and evaluate the analgesic, anti-inflammatory, and antipyretic properties of the aqueous extract of Combretum collinum (AECC) leaves in an animal model. The phytochemical analysis was performed using LC-MS and safety assessment (acute and subacute toxicity) of AECC were conducted according to standard scientific procedures (OECD guidelines). Analgesic and anti-inflammatory effects was determined via formalin-induced assay, while the antipyretic activity used turpentineinduced fever model. Diclofenac (15mg/kg) served as a reference drug. No acute toxicity symptoms were observed after the oral administration of AECC at a dose of 2000mg/kg. In the sub-acute study, AECC extract showed no mortality or treatment-related adverse effects on general behavior, body weight, relative organ weights, and hematological and biochemical parameters. The analgesic activity of the AECC extract at 50, 100, and 150mg/kg resulted in a pain response reduction of 40.37 %, 39.89 %, and 40.38 %, respectively, in the acute phase, while the chronic phase demonstrated dose-dependent pain inhibition (p ≤ 0.05). The AECC extract also lowered rectal temperature in the antipyretic activity to 3.14 %, 3.61 %, and 3.86 %, respectively, for the same doses. AECC exhibited anti-inflammatory activity with reductions in formalininduced paw edema of 0.68 %, 0.69 %, and 0.68 % at 50, 100, and 150mg/kg, respectively. This study concludes that there are no acute or sub-acute toxicity symptoms associated with AECC and demonstrates its analgesic, anti-inflammatory, and antipyretic effects, indicating its potential application as a viable therapeutic agent