Temporal Variation of Methanogenic Microbial Community in Palm Oil Mill Effluent (POME) Anaerobic Digester

Palm Oil Mill Effluents (POME) serve as suitable substrates for methane gas production through anaerobic digestion. This process relies on a complex microbial community that plays a critical role in ensuring stable anaerobic digester operation and efficient biogas production. Among these microorganisms, methanogenic archaea are pivotal in methane generation by utilizing diverse substrates under anoxic conditions. However, the knowledge of the microbial communities, particularly those involved in methane production in POME anaerobic sludge at different time intervals, remains limited. This study aims to uncover temporal variations in microbial communities, including diversity, composition, and structure, within POME anaerobic sludge, specifically focusing on the methanogenic archaea community. The temporal dynamics of microbial communities in the eighteen POME anaerobic sludge samples collected from a palm oil mill were investigated through 16S rRNA amplicon sequencing. The results reveal consistent microbial community diversity in POME anaerobic sludge over the study periods. Then, the sequencing also showed that Bacillota (26.9 ± 3.3%), Bacteroidota (20.2 ± 5.3%), and Chloroflexota (15.0% ± 6.3%) were the dominant bacterial phyla in POME anaerobic sludge across different time frames. Concurrently, Halobacteriota (5.9 ± 2.8%), Methanobacteriota (2.5 ± 0.6%), and Nanoarchaeota (2.3 ± 1.2%) were the primary archaeal phyla identified in anaerobic sludge at various time intervals. Furthermore, amplicon sequencing revealed the presence of two methanogenic archaea genera, Methanothrix and Methanobacterium, associated with acetoclastic and hydrogenotrophic methanogenesis, respectively. These findings suggest that acetoclastic and hydrogenotrophic methanogenesis pathways are the primary contributors to methane production in the POME anaerobic digestion process.