Yeast fermentation towards biodiesel: Maximizing resource recovery by integrating with biohydrogen production in biorefinery framework

Abstract

This study presents an effective and sustainable approach for biodiesel production through oleaginous yeast fermentation by utilizing volatile fatty acids (VFAs) rich acidogenic effluents as an alternative feedstock. Experiments were designed in two stages to obtain high cell density and lipid productivity. Primarily, oleaginous yeast (Cryptococcus curvatus; MTCC 2698) was grown on glucose with varied initial concentrations at 25 °C. Maximum biomass concentration of 4.2 ± 0.05 g/L was achieved with 40 g/L glucose, which was subjected to the second stage along with the supplementation of 5 g/L of selected VFAs viz., acetic acid, propionic acid, butyric acid and mixed VFAs. Highest lipid concentration of 33.5% (w/w) was obtained with acetic acid supplementation followed by mixed VFAs (23% w/w). Further, to validate results from initial studies, yeast strain was cultivated on real field VFAs rich acidogenic effluent derived from renewable biohydrogen production process. Maximum of 4.85 ± 0.05 g/L biomass and 29.3% (w/w) of lipid was observed during real field application fatty acid profiling of produced lipids showed predominance of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2) which has potential utility for biodiesel production. Integration of bioprocesses in a biorefinery format helps to maximize resource recovery apart from minimizing waste generation. The study confirms feasible utilization of acidogenic effluent as an alternative feedstock for the production of microbial lipids through yeast fermentation.