Improving anaerobic digestion performance of cassava residues through utilization of photosynthetic bacteria under varying light intensities

Photosynthetic bacteria were employed as biological enhancers to investigate the anaerobic digestion performance of cassava residues under varying light intensities. Based on the four levels of light intensity (0, 1500, 3000, and 6000 lx), Rhodopseudomonas palustris was used to biofortify anaerobic digestion . The anaerobic digestion process was analyzed in terms of volatile fatty acid accumulation and transformation, enzyme content, extracellular polymer composition, and microbial community . The results showed that the addition of Rhodopseudomonas palustris increased biogas production and accelerated the removal of fatty acid inhibition, even in the absence of light. Biogas production was positively correlated with light intensity. Biogas production under a light intensity of 6000 lx was 20.91 % higher than without light, and the fermentation period was shortened by 10 d. The enzyme concentrations and extracellular polymeric substance characteristics were influenced by light irradiation. Light irradiation altered the bacterial community structure. The dominant methanogenic archaea shifted from Methanosaeta to Methanosarcina . • PSB increased biogas production and expedited the recovery of AD from acidosis. • Light at an intensity of 6000 lx increased biogas production by 20.91 %. • Light at an intensity of 6000 lx shortened the AD time length by approximately 10 days. • The concentration of protein and polysaccharide in the TB-EPS was increased. • Light irradiation altered the community structure at the genus level of bacteria.