Culture of acetogenic complex strains Th3 and its application in biogas production

In order to improve conversion rate of acetic acid and methane yield in anaerobic digestion, an atificial composite system Th3 was constructed by mixing three strains of acetogenic bacteria CD-2 (Clostridium sordellii), ZY-3(Clostridium bifermentans) and ZQ-1 (Clostridium butyricum). The experimental results showed that the optimum fermentation conditions of Th3 were as follows：initial pH was 7.0-8.0, sequence of three bacteria inoculation was ZQ-1, ZY-3 and CD-2, inoculation ratio was 1:2:1, and inoculum was 6% of effective volume. At the same time, the acetic acid yield was observed as high as 0.65 g/(L·d) at 30°C with static culture. The metabolic process of Th3 was proved to be very stable within ten generations. At(26±1)°C, the daily biogas production and productivity were improved significantly after Th3 addition in the initial and medium fermentation, and the start-up phase was shortened by 2-3 days. But the biogas process had no significant change when Th3 was added at the late stage of fermentation. The research can provide a reference for the complex strains construction, anaerobic digestion efficiency improvement and optimization of fermentation process and has an application value in biogas production.