Deciphering synergistic effect of indigenous and polymer-degrading bacteria in vermicomposting via metagenomic sequencing for sustainable strategies of plastic waste management

Currently there is no information available on the fate of bio-based plastic bags in home composting system after compost maturation. The slow decomposition period for bio-bags (90 days) highly depends on weather conditions and biological processes. Therefore, additional players such as earthworms and metabolically-active bacteria need to be added to accelerate the decomposition. Unfortunately, the performance of epigeic earthworms, Perionyx excavatus, in devouring bio-bags and the microbial interaction between earthworm gut microbiome and metabolically-active bacteria upon the introduction of bio-bags are unclear. Considering the downstream application of compost as soil amendments, it is very important to evaluate the safety of compost after adding bio-bags as substrate. Thus, the objectives of this research are to determine the microbial community shifts in vermicomposting system upon introduction of bio-bags and epigeic earthworms, to compare the structural integrity of bio-bags during active composting, and to determine physico-chemical properties of final compost as non-toxic soil amendments. Methodologies include DNA extraction and amplicon sequencing from the soil and inner-gut lining of earthworms and comparing the microbial C-metabolic activity for bacterial community analyses; SEM and FTIR analyses for evaluation of surface structure and chemical composition of bio-bags during decomposition period, respectively; physico-chemical analyses such as pH, electrical conductivity, total organic carbon, and plant toxicity tests. At the end of the study, we expect to elucidate and bio-prospect degrading taxa and communities for environmental and biotic manipulation as well as potential use of dominant degraders in biorefineries in Malaysia while providing an alternative solution to plastic waste mismanagement in the country. Elucidating the potential of accelerated bio-bag decomposition via vermicomposting may also project less reliance on conventional plastic bags and a more favorable shift towards circular bio-economy (KEGA 12) and sustainable plastic cycles that bio-bags generated by providing evidence that composts from bio-bags are non-toxic as soil amendment.