Mapping microbial dynamics in anaerobic digestion system linked with organic composition of substrates: Protein and lipid

Considering the energy potential and anaerobic biodegradability, protein and lipid are among the most significant organic components of many biogas feedstocks. Although the two core organics have typical structures, each category has compositional variations according to the source, and thus has different biogas potential and catabolic microbes. Therefore, this study analyzed the characteristics and biogas potential of ten model substrates: casein, gelatin, gluten, whey and pork liver as protein-rich (60.1 ± 42.6%) substrates and glycerol, fish oil, soybean oil, butter and pork fat as lipid-rich (72.1 ± 40.5%) substrates. During the digestion process, the maximum methane production and its production rate were 2 and 1.6 times higher in the lipid-rich group, while the lag phase was >2 times longer in the same group. The microbial community structure, determined by high-throughput sequencing, was clustered depending on the organic majority (either protein or lipid), with minor differences within the cluster. The protein-rich and lipid-rich substrates were estimated to generate energy up to 19910 and 7781.8 kJ/kg, respectively, based on the energy analysis. Overall, the complex biochemical process of anaerobic digestion will be better understood based on the proposed microbial dynamics concerning different organic substrate compositions.