Study on biodegradation of used engine oil in a stirred batch bioreactor by ochrobactrum intermedium and Bacillus paramycoides isolates

Engine oil is a significant environmental contaminant, and its removal is challenging due to its persistent nature in the ecosystem. Engine oil is a significant environmental contaminant, and its removal is challenging due to its persistent nature in the ecosystem. Biodegradation of used engine oil using indigenous bacteria from contaminated soil is a cost-effective approach for environmental cleanup. This study investigated the efficiency of a single bacterial isolate and a formulated bacterial consortium (BC), both sourced from the contaminated soil of a mechanical workshop, in the biodegradation of engine oil. The bacterial strains were identified by 16 S rDNA sequencing as Ochrobactrum intermedium LMG 3301 and Bacillus paramycoides MCCC1A04098/BC. Additionally, the study sought to evaluate the growth and physiological activity of the oil-degrading bacteria in the stirred batch bioreactor (SBR) both individually and in consortia. The biodegradation of 0.675% of used engine oil, bacterial growth, and enzymatic activity was achieved under elevated aerobic conditions and optimal environmental factors for 0-5 days. The BC was more efficient at biodegrading used engine oil with 10% (85%) TPH increased removal compared to O. intermedium (77%) in a stirred batch bioreactor at pH 7.5, temperature 37 °C, and inoculum size 15 ml of OD600nm = 1. The results showed that consortium and single bacteria could both degrade longer-chain alkanes, but their abilities to handle shorter-chain alkanes varied. While a consortium generates more lipase enzymes, a single bacterium produces more dehydrogenase, which is connected to energy generation in the form of NADPH. As a result, O. intermediate bacterium expends a large deal of effort to break down the oil on its own. The single's faster growth rate and shorter doubling time compared to the consortium indicate the efficacy and growth abilities of O. intermedium when given a UEO substrate. However, the consortium's slower growth rate and longer doubling time were likely brought on by either the slower-growing partner or the length of time it takes for a syntrophic relationship to develop. The study demonstrated the bioeffectiveness of using a sequencing batch bioreactor for heavy UEO elimination and offered two distinct bacteria formulations for successful bioremediation of hazardous pollutants.