Optimization of Growth Conditions for Chlorpyrifos-Degrading Bacteria in Farm Soils in Nakuru County, Kenya
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Date
2024-01
Authors
Wachira, Peter
Huria, Nderitu
Sifuna, Paul
Essuman, Suliman
Asamba, Micah
Journal Title
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Publisher
Hindawi
Abstract
Chlorpyrifos (CP) is a chlorinated organophosphate pesticide. In Kenya, it is commonly used as an acaricide, particularly in dairy
farming, leading to soil and water contamination. The study is aimed at isolating bacteria with CP-degrading potential and
optimizing their growth conditions, including temperature, pH, and CP concentration. The enrichment culture technique was
used, with minimal salt medium (MSM) supplemented with commercial grade CP. A multilevel factorial design was used to
investigate the interactions of temperature, pH, and CP concentration. According to the findings, seven bacterial strains with
potential to degrade CP were characterized and identified as Alcaligenes faecalis, Bacillus weihenstephanensis, Bacillus
toyonensis, Alcaligenes sp. strain SCAU23, Pseudomonas sp. strain PB845W, Brevundimonas diminuta, and uncultured
bacterium clone 99. Growth and biodegradation of bacteria differed significantly among the isolates across pH value,
temperature, and concentrations (P ≤ 0 05). The optimum conditions for growth were pH 7, temperature of 25°
C, and 25mg/l
chlorpyrifos concentration, while optimum degradation conditions were pH 5, temp 25°
C, and CP conc. 25mg/l. The Pearson
correlation between optimum growth and degradation showed a weak positive relationship (R = 0 1144) for pH and strong
positive relationship for temperature and concentration of chlorpyrifos. Other than pH, the study shows that there could be
other cofactors facilitating the chlorpyrifos degradation process. The findings show that an efficient consortium, at 25°
C and
pH 5, can include Bacillus toyonensis 20SBZ2B and Alcaligenes sp. SCAU23 as they showed high optical density (OD) values
under these conditions. These results indicate the potential for these bacteria to be employed in chlorpyrifos-contaminated
ecosystem detoxification efforts upon manipulation of natural growth conditions. The findings of this study offer a potential
foundation for future research into the reconstitution of a consortium. Based on the optimum conditions identified, the
isolated bacterial strains could be further developed into a consortium to effectively degrade CP in both laboratory and field
conditions. Dairy farmers can utilize the isolated strains and the consortia to decontaminate farm soils
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Citation
Wepukhulu, M., Wachira, P., Huria, N., Sifuna, P., Essuman, S., & Asamba, M. (2024). Optimization of Growth Conditions for Chlorpyrifos-Degrading Bacteria in Farm Soils in Nakuru County, Kenya. BioMed Research International, 2024.