Effects Of Yeast Fermentation on Caproic Acid Production And Microbial Community During the Anaerobic Digestion of Chinese Cabbage Waste

Abstract

To provide a sufficient supply of electron donors for the synthesis of caproic acid, this study employed yeast to increase ethanol production in the anaerobic fermentation of Chinese cabbage waste (CCW). The results showed that the caproic acid yield of CCW with yeast pre-fermentation reached 7750.3 mg COD/L, accounting for 50.2% of the total volatile fatty acids (TVFAs), which was 32.5% higher than that without yeast. The simultaneous fermentation of yeast and seed sludge severely inhibited the formation of butyric acid, thus limiting the synthesis of caproic acid. In the reactor employing the condition of yeast pre-fermentation as well as the reactor without yeast, ethanol depletion was key to limiting caproic acid synthesis. Yeast fermentation inhibited substrate degradation and TVFAs production. In the reactor with yeast pre-fermentation, Prevotella played an important role in substrate degradation, while Clostridium_sensu_stricto_12 was determined to be the dominant bacteria responsible for caproic acid synthesis.

Keywords: anaerobic digestion, Electron donor, Caproic acid, Yeast fermentation, Chinese cabbage waste