Synergistic effect of syntrophic acetogenesis and homoacetogenesis for volatile fatty acids production from sludge by anaerobic digestion

By using metabolic inhibitor (BES) to block the methanogenesis and adding butyrate to enhance syntrophic acetogensis, syntrophic acetogens/homoacetogens synergism during the acidification fermentation of sludge from anaerobic digestion was investigated and then the acetate accumulation mechanism was clarified. The results indicated that the acetate concentration was 6 g·L^-1 in the condition of the ΔG was about -15 kJ·mol^-1 and no methanogens, and the proportion of acetate were produced by syntrophic acetogens and homoacetogens is 7:3. However, the syntrophic acetogens/homoacetogens synergism did not occur under the condition of H₂ pressure was 3.2 kPa, the butyrate concentration was 4 g·L^-1 and the acetate concentration was 6 g·L^-1. The acetate can be produced by the syntrophic acetogens/homoacetogens synergism but it is restricted.