Immobilization of trophic anaerobic acetogen for semi-continuous syngas fermentation

Abstract

Abstract The massive consumption of fossil energy forces people to find new sources of energy. Syngas fermentation has become a hot research field as its high potential in renewable energy production and sustainable development. In this study, trophic anaerobic acetogen Morella thermoacetica was successfully immobilized by calcium alginate embedding method. The ability of the immobilized cells on production of acetic acid through syngas fermentation was compared in both airlift and bubble column bioreactors. The bubble column bioreactor was selected as the better type of bioreactor. The production of acetic acid reached 32.3 g·L−1 in bubble column bioreactor with a space–time yield of 2.13 g·L−1·d−1. The immobilized acetogen could be efficiently reused without significant lag period, even if exposed to air for a short time. A semi-continuous syngas fermentation was performed using immobilized cells, with an average space–time acetic acid yield of 3.20 g·L−1·d−1. After 30 days of fermentation, no significant decrease of the acetic acid production rate was observed.