Effects of Syngas on Homoacetogenesis in Mixed Bacteria Fermentation

Abstract

This study used mixed bacterial species as inoculum to explore the effects of headspace H2/CO2 ratio, carbon source types, and pH on the product synthesis by homoacetogenic bacteria. The results showed that high pH was conducive to the autotrophic reactions of homoacetogenic bacteria using H2/CO2 mixed gas. When pH=7, H2/CO2=3:1, volatile fatty acids (VFAs) exhibited the highest yield of 1383.83 mg/L, which the acetic acid yield accounted for the largest proportion in the total VFAs (76.1%). When glucose and H2/CO2 mixed gas were used as the common carbon source, homoacetogenic bacteria preferentially used glucose to conduct homoacetogenesis reaction.The correlation analysis showed that VFA contents were extremely significantly correlated with pH,negatively correlated with H2/CO2. In addition, this study established a back propagation (BP) neural network for the homoacetogenesis reaction, which could accurately predict the VFA yield synthesized by homoacetogenic bacteria when H2/CO2 mixed gas was used as the carbon source (R2=0.96584).

Keywords: homoacetogenesis, Anaerobic fermentation, syngas, pH