Syntrophic relationship among microbial communities enhance methane production during temperature transition from mesophilic to thermotolerant conditions
Gede Adi Wiguna Sudiartha, Tsuyoshi Imai, Alissara Reungsang
Abstract
Hydrogenotrophic methanogenesis, in a syntrophic relationship with fermentative and acetogenic bacteria, is an essential key for maximizing biogas production and reducing CO 2 emissions. However, its impact on CH 4 production under varying temperatures is not widely understood. This study investigates the effects of incremental temperature transition from 37 °C to 45 °C at 2 °C intervals, on anaerobic digestion (AD) using digested sewage sludge with low glucose addition. Results showed CH 4 production levels of 298 and 309 ml CH 4 /g COD fed at 37 °C and 39 °C, respectively, and exhibited a decrease at 41 °C. A temperature increase to 43 °C restored CH 4 production to 260 ml CH 4 /g COD fed , with lower CO 2 output. At 45 °C, the CH 4 - CO 2 production gap widened, indicating enhanced methanogenic activity due to prolonged high temperatures. Methanothrix was the predominant methanogen, followed by Methanobacterium whose activity increased at 43 °C and 45 °C alongside the upregulation of key hydrogenotrophic pathway enzymes (fwd, ftr, mch ). The increasing abundance of fermentative bacteria at 43 °C and 45 °C may upregulates hydrogenotrophic methanogenesis. Flux balance analysis revealed the role of Acetomicrobium and Clostridia sp. strains that supplied the most acetate, providing approximately 7 – 600 mmol/gDW/h to the microbial communities. These findings highlight the adaptability of microbial communities and possible syntrophic relationships in response to temperature changes, demonstrating the resilience of AD processes under varying environmental conditions. • Higher temperatures with long incubation periods enhance CH 4 production with lower CO 2 emissions. • 16S rRNA sequencing followed by functional annotation and flux balance analysis was performed. • Methanothrix and Methanobacterium dominated the methanogens communities. • Acetomicrobium, Defluviitoga, Coprothermobacter, and Candidatus sp. showed putative syntrophic relationship to hydrogenotrophic methanogens at higher temperatures. • Increasing metabolic exchanges of amino acids at higher temperatures upregulates CH 4 production.