Mesophilic Versus Thermophilic Anaerobic Digestion of Soybean Curd Residue for Methane Production: Characterizing Bacterial and Methanogen Communities and Their Relationship with Organic Loading Rates

How to economically and effectively treat huge amount of soybean curd residue (SCR) is a current major challenge to the soybean products processing plants throughout the world due to the fact that the uncontrolled disposal of SCR is liable to cause adverse environmental impacts and threaten the public health. To find the optimal operation parameters for anaerobic digestion of SCR, mesophilic (35⁰C) versus thermophilic (55⁰C) anaerobic digestion (AD) of SCR for methane production were contrastively investigated for 95 days with an increasing organic loading rate (OLR) from 0.55 to 4.96 gVS/L. Anaerobic digestion performance of SCR indicated that the maximum available OLR was 3.3 gVS/L for both mesophilic and thermophilic AD. Thermophilic AD provided a higher methane yield and volatile solids removal than that of mesophilic AD. The first dominant volatile fatty acid was identified as acetic acid. In addition, an in-depth understanding of the microbial compositions, diversity/similarity, and relations between digester performance, biodiversity and environmental parameters at the genome level was obtained by pyrosequencing technique and bioinformatics analysis, which would help to optimize microbial productivity and maximize the methane yield in the anaerobic digestion process of the SCR.