Integrated anaerobic membrane bioreactor-yeast biorefinery for co-production of hydrogen, volatile fatty acids, and microbial oil from food waste

With growing food waste challenges globally, acidogenic fermentation using an anaerobic membrane bioreactor (AnMBR) was developed for the co-production of hydrogen, volatile fatty acids (VFAs), and microbial oil from food waste. Batch experiments identified optimal conditions of pH 6.0 and substrate/inoculum ratio of 3:1, which were applied in a semi-continuous AnMBR with in situ VFA recovery. At an organic loading rate of 3.3 g-VS L^-1·d^-1, the system achieved hydrogen production of 223.9 ± 3.4 mL L^-1·d^-1 and VFA productivity of 1.68 ± 0.15 g-COD_VFA L^-1·d^-1. A critical total suspended solids threshold of 15.7 g L^-1 was identified for stable membrane performance. The VFA-rich permeate was dominated by acetic and butyric acids. Cultivation of Candida tropicalis on the VFA-rich permeate resulted in biomass and lipid yields of 0.47 and 0.15 g g-VFA_consumed^-1, respectively, with 94.2% VFA consumption. These findings indicate that the integrated AnMBR-yeast system offers promising potential as a biorefinery platform for converting food waste into multiple value-added bioproducts.