Hydrolytic enzyme profiling of Bacillus subtilis COM6B and its application in the bioremediation of groundnut oil mill effluent

Abstract

Industrial effluents rich in oil and grease pose hindrance to the functioning of wastewater treatment units and also affect the quality of receiving water bodies. Pretreatment of such wastewaters to bring about lipid hydrolysis makes them more amenable to conventional biological treatment and hydrolytic enzymes, especially lipases, find promising applications in this sector. In our study, the bacterial strain Bacillus subtilis COM6B isolated from groundnut mill effluent was cultivated in minimal media based on residual oil waste from the extraction process, in which it produced lipase and other extracellular hydrolytic enzymes such as protease and amylase. Applying response surface methodology led to a 1.8-fold increase in oil waste removal by the isolate. As a further study, the effluent discharged from the oil mill was treated in batch mode using pure cultures of the isolate and the effects of incubation time, inoculum size and effluent dilution on the treatment process were investigated. A maximum of 95, 93 and 98 % reduction in biochemical oxygen demand, chemical oxygen demand and oil and grease respectively, were achieved after treatment with COM6B. Hence, the isolate could serve as a potential candidate for remediating the fat and oil contaminants and reducing the organic load of wastewaters.