Insights into microbial community structure and diversity in oil palm waste compost

Empty fruit bunch (EFB) and palm oil mill effluent (POME) are the major wastes generated by the oil palm industry in Malaysia. The practice of EFB and POME digester sludge co-composting has shown positive results, both in mitigating otherwise environmentally damaging waste streams and in producing a useful product (compost) from these streams. In this study, the bacterial ecosystems of 12 week-old EFB-POME co-compost and POME biogas sludge from Felda Maokil, Johor were analysed using 16S metagenome sequencing. Over 10 phyla were detected with Chloroflexi being the predominant phylum, representing approximately 53% of compost and 23% of the POME microbiome reads. The main bacterial lineage found in compost and POME was Anaerolinaceae (Chloroflexi) with 30% and 18% of the total gene fragments, respectively. The significant differences between compost and POME communities were abundances of Syntrophobacter, Sulfuricurvum, and Coprococcus. No methanogens were identified due to the bias of general 16S primers to eubacteria. The preponderance of anaerobic species in the compost, and high abundance of secondary metabolite fermenting bacteria is due to an extended composting time, with anaerobic collapse of the pile in the tropical heat. Predictive functional profiles of the metagenomes using 16S rRNA marker genes suggest the presence of enzymes involved in polysaccharide degradation such as glucoamylase, endoglucanase, arabinofuranosidase, all of which were strongly active in POME. Eubacterial species associated with cellulytic methanogenesis were present in both samples.