Dose-response effects of microaeration on thermophilic lignocellulose-based anaerobic digestion: performance, stability and microbial community dynamics

Microaeration has emerged as a promising strategy for enhancing anaerobic digestion (AD) of lignocellulosic biomass, although inconsistent results highlight the need for further study. This study tested three different aeration rates (1, 5 and 8 mLO 2 /gVS) on anaerobic co-digestion of wheat straw and cattle manure under thermophilic conditions (55 °C) in continuous-stirred tank reactors with working volume of 60 L. Daily injection of 5 mLO 2 /gVS achieved the highest methane yield, with a 20.6% increase compared to the non-aerated control digester. Under these conditions, cellulose and hemicellulose degradation reached maximum levels of 75% and 66.3%, respectively. In the microaerated digester, remarkable changes in microbial population were observed. Injection of 1 mLO 2 /gVS and 5 mLO 2 /gVS increased the relative abundance of Lentimicrobium , Turicibacter , and unclassified MBA03 as well as hydrogenotrophic Methanothermobacter which could contribute to enhanced lignocellulose degradation and biogas generation. At the final and highest oxygen dose (8 mLO 2 /gVS), methane yield began to gradually decrease. Under these conditions, the microbial profile shifted back to that of the non-aerated digester, suggesting that the activity of certain microbial groups was inhibited. These findings highlight the potential of controlled microaeration to enhance both methane yield and lignocellulosic degradation at larger scales, offering valuable insights for optimizing AD processes.