Production of potential fuel oils by Rhodococcus opacus grown on petroleum processing wastewaters

Abstract

The wastewater of a petroleum processing facility was used to grow the oleaginous bacterium Rhodococcus opacus PD630 to produce microbial oils. Undiluted wastewater supplemented with molasses (20 g/l) and ammonium chloride (1 g/l) provided a maximum dry biomass concentration of nearly 6 g/l in a 96 h batch culture. The lipid concentration in the bacterial broth exceeded 3 g/l and the lipid content in the dry biomass was nearly 52% by weight. Biomass and oil production were further improved using a 96-h fed-batch fermentation instead of a batch culture. The final biomass concentration exceeded 7.2 g/l and the lipid concentration was nearly 4 g/l. The lipid content of the dry biomass exceeded 54% and the lipid yield on sugars was 0.33 g/g. The lipids were similar to vegetable oils. They contained mainly long chain C16 and C18 fatty acids. Potentially such lipids may be used to replace vegetable oils in production of biodiesel.