Enhanced succinic acid production from polyacrylamide-pretreated cane molasses in microbial electrolysis cells

BACKGROUND: Microbial electrolysis cells (MECs) are bioelectrochemical reactors in which chemical energy stored in organic compounds is converted to hydrogen through biocatalytic oxidation by microorganisms. This study is the first to report on the practical application of an electric MEC bioreactor to succinic acid anaerobic fed-batch fermentation from polyacrylamide-pretreated cane molasses by Actinobacillus succinogenes (130Z). RESULTS: When molasses was used as the carbon source with an initial sugar concentration of 15 g L^-1, the succinic acid concentration was 22.4% higher in electric MECs than in non-electric MECs. However, the high molasses concentration inhibited the function of MECs. Nevertheless, anionic polyacrylamide (APAM) pretreatment of molasses was noted to be effective for succinic acid production in MECs even at an initial sugar concentration of 75 g L^-1. Therefore, fed-batch fermentation of APAM-pretreated cane molasses with electric MECs at −1.0 V was performed, and a succinic acid concentration of 83.67 g L^-1 and productivity of 1.743 g L^-1 h^-1 were obtained, which were 20.7% and 505% higher than those achieved in non-electric MECs and without pretreated molasses in MECs, respectively. CONCLUSION: The succinic acid concentration is significantly increased in electric MECs. Polyacrylamide treatment strategy can resolve the inhibition of high molasses concentration to succinic acid production in MECs and might be an effective method for improvement of chemical production from high hydrolysate content using MECs. Fed-batch fermentation with polyacrylamide-pretreated cane molasses in electric MECs is noted to be ideal to achieve further increase in succinic acid concentration and yield.