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 (). 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 () 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.

中文翻译：

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肯尼亚纳库鲁县农田土壤中毒死蜱降解细菌生长条件的优化

毒死蜱（CP）是一种氯化有机磷农药。在肯尼亚，它通常被用作杀螨剂，特别是在奶牛养殖中，导致土壤和水污染。该研究旨在分离具有 CP 降解潜力的细菌，并优化其生长条件，包括温度、pH 值和 CP 浓度。使用富集培养技术，并添加商业级 CP 的最低盐培养基 (MSM)。使用多水平因子设计来研究温度、pH 值和 CP 浓度的相互作用。根据研究结果，对 7 株具有降解 CP 潜力的细菌进行了表征和鉴定，分别为粪产碱菌 (Alcaligenes faecalis)、魏氏芽孢杆菌 ( Bacillus weihenstephanensis )、丰氏芽孢杆菌 (Bacillus toyonensis )、产碱菌(Alcaligenes sp)。菌株SCAU23，假单胞菌属。菌株PB845W、Brevundimonas diminuta和未培养的细菌克隆 99。细菌的生长和生物降解在 pH 值、温度和浓度方面存在显着差异（）。最佳生长条件为pH 7、温度25℃、毒死蜱浓度25mg/l；最佳降解条件为pH 5、温度25℃、CP浓度。25毫克/升。最佳生长和退化之间的 Pearson 相关性显示出弱正相关（)的 pH 值与温度和毒死蜱浓度呈强正相关关系。除 pH 值外，研究表明可能还有其他辅助因子促进毒死蜱的降解过程。研究结果表明，在 25°C 和 pH 5 下，一个有效的联合体可以包括Bacillus toyonensis 20SBZ2B和产碱菌sp。SCAU23在这些条件下表现出高光密度 (OD) 值。这些结果表明，通过控制自然生长条件，这些细菌有可能用于受毒死蜱污染的生态系统解毒工作。这项研究的结果为未来研究联盟的重组提供了潜在的基础。基于确定的最佳条件，分离的细菌菌株可以进一步发展成一个联合体，以在实验室和现场条件下有效降解CP。奶农可以利用分离的菌株和菌群来净化农场土壤。