Optimization of the process conditions for biodegradation of phenolic compounds in olive mill wastewater using Bacillus subtilis in bioreactor cultures

Olive mill wastewater (OMWW) poses serious environmental problems due to the presence of high phenolic compounds (PC) content. The search for new strains able to degrade pollutants in OMWW and withstand the toxic effects of the high PC concentrations is of great scientific and industrial interest. In this study, an isolated bacterium identified as Bacillus subtilis was selected based on its ability to grow on minimum synthetic medium based media using PC as sole sources of carbon and energy and to degrade the OMWW. The treatment conditions were optimized and included the following parameters: OMWW dilution with the addition of different nitrogen sources, shaking and incubation temperatures. The maximum abatement rate of PC and chemical oxygen demand was 98% and 97%, respectively. This result was obtained at 25% dilution of OMWW with 1 mL inoculums size in a bioreactor with150 rpm, at 37 degrees C with the addition of the degradation media with 1 g/L yeast extract and 3 g/L urea. High-performance liquid chromatography analysis of extracts from treated OMWW showed the evolution of PC content during the degradation process and indicated the high reduction in phenolic compound concentrations.