Biogas upgrading and biochemical production from gas fermentation: impact of microbial community and gas composition

The present study proposes a novel alternative method of the current biogas upgrading techniques by converting
CO2 (in the biogas) into valuable chemicals (e.g., volatile fatty acids) using H2 as energy source and acetogenic
mixed culture as biocatalyst. The influence of thermal treatment (90 °C) on the inhibition of the methanogenic
archaea and enriching the acetogenic bacteria in different inocula (mesophilic and thermophilic) was initially
tested. The most efficient inoculum that achieved the highest performance through the fermentation process was
further used to define the optimum H2/CO2 gas ratio that secures maximum production yield of chemicals and
maximum biogas upgrading efficiency. In addition, 16S rRNA analysis of the microbial community was conducted
at the end of the experimental period to target functional microbes. The maximum biogas content (77%
(v/v)) and acetate yield (72%) were achieved for 2H2:1CO2 ratio (v/v), with Moorella sp. 4 as the most dominant
thermophilic acetogenic bacterium.