Feasibility of m-cresol degradation using an indigenous mixed microbial culture with glucose as co-substrate

Abstract

An indigenous mixed culture of microorganisms, isolated from the soil of a gasoline filling station, was used in degrading m-cresol in presence of glucose as an alternative carbon source. Initial glucose concentration was kept at either 250 or 500 mg l−1, to initiate and support necessary culture growth, and that of m-cresol was varied between 50 and 400 mg l−1. A maximum total biomass yield value of 0.925 g g−1 was obtained at 100 mg l−1m-cresol and 500 mg l−1 glucose initial concentrations in the media. Variation in the experimentally observed specific growth rate revealed that m-cresol initial concentrations, above 100 mg l−1, inhibited the culture growth irrespective of the glucose concentrations used in the study. Complete degradation of m-cresol was observed within a time period of 18–26 h depending upon the initial concentrations of m-cresol and glucose in the media; on the other hand, glucose utilization was quick and preceded m-cresol degradation. A sum kinetics model was used to describe the variation in the culture specific growth rate, which gave a high coefficient of determination (R2) value >0.98. From the interaction parameter values obtained by solving this model, the inhibitory effect of glucose on m-cresol degradation by the culture was found to be more pronounced compared to the effect of m-cresol on glucose utilization. This study showed good potential of the indigenous mixed culture in degrading m-cresol when it is provided with a simple alternative carbon source, such as glucose, for supporting its growth.