Stepwise Acclimatization of Mesophilic to Thermophilic Conditions for Improved Biogas Production from Cassava Pulp

Cassava pulp contains a high proportion of lignocellulosic compounds (26–32%), which are difficult to degrade and thus limit the efficiency of biogas production under mesophilic conditions. These limitations include the inability to apply high organic loading rates (OLR) and the requirement for long hydraulic retention times (HRT). Operating anaerobic digestion systems under thermophilic conditions is a promising approach, as most hydrolytic enzymes exhibit higher activity at elevated temperatures. However, successful thermophilic digestion depends on the ability of microbial communities to function under such conditions.

This study aimed to acclimatize mesophilic microbial consortia to thermophilic conditions through stepwise temperature elevation. The results showed that the reactor operated at 60°C achieved the highest hydrolysis efficiencies of starch, cellulose, and hemicellulose (99%, 58%, and 58%, respectively). Nevertheless, the reactor at 50°C was found to be optimal for methane production, providing the best balance between system performance and operational stability. Microbial community analysis revealed that Bacteroidota was the dominant phylum under mesophilic conditions, whereas Chloroflexi predominated under thermophilic conditions. These findings suggest that microbial acclimatization can enhance the degradation efficiency of cassava pulp and enable stable high-temperature anaerobic digestion suitable for high OLR applications.