Biodegradation Potential of Bacterial Isolates from Inner Tub of Washing Machines on Detergent, Spent Engine Oil, and Pesticide

Abstract

Bacteria inhabiting washing machines are constantly exposed to chemically diverse substances including surfactants from detergents which may promote the development of adaptive traits. These machines remain an underexplored niche for biodegradation and biotechnological application. Therefore, this study investigated the biodegradation potential of bacteria isolates from inner tub of washing machines on detergent, spent engine oil and pesticide using standard methods. Pseudomonas putida showed the highest biodegradation rate of 40.20 % and 24.90 % for detergent and spent engine oil respectively, while Alcaligenes faecalis recorded the highest pesticide degradation rate of 29.55%. The other isolates also exhibited different rate of degradation potentials compared with Bacillus subtilis used as the control strain.  The highest optical density at 300C was recorded for B. subtilis (2.48±0.000), followed by A. faecalis (2.43±0.000) in pesticide-supplemented medium. The highest bacterial growth was observed with Bacillus subtilis in pesticide-supplemented medium at pH 4.5, followed by pH of 7.5at optical densities of 2.650±0.000 and 2.215±0.000 respectively. The highest growth rate was observed at an inoculums size of 1.0mL for B. subtilis (3.344±0.000), followed by Proteus mirabilis BLS103C (2.372±0.000). Glucose and peptone produced the highest optical densities as carbon and nitrogen sources respectively. The results obtained from optimization experiments were statistically significant at p˂0.05. These findings showed that washing machines harbor resilient adaptive traits for biodegradation of different substrates used in this study. Their enhanced growth highlights their potential applications in environmental bioremediation and industrial biotechnology.