Microbial acclimation of thermophilic anaerobic digestate enhances biomethane production and biodegradation of polylactic acid in combination with organic wastes

Co-digestion of bioplastics alongside food waste (FW) is crucial to improve waste management practices in the context of the circular economy. In this study, three anaerobic digestion (AD) runs were conducted sequentially to investigate the effects of inoculum acclimation on enhancing polylactic-acid (PLA) and FW degradation in mono and co-digestion (PLA+FW). Microbial acclimation lead to an enhanced degradation of PLA with a +115-152% increase of biogas which was correlated with the growth of PLA degrading bacteria such as Tepidanaerobacter. The production of biogas of PLA+FW was increased by +69% and was associated with the growth of both PLA and protein degraders such as Halocella and Acetomicrobium. FW acclimation lead to an increase of cumulative biogas of +20%, and it was related to the growth of protein degraders such as Halocella and Keratinibaculum. All communities were characterized by the presence of methanogens highlight resistant to high ammonia concentrations with Methanoculleus possibly enhancing methane production. Overall, this research highlighted the promising role of microbial acclimation as a cost-efficient and environmentally friendly approach to improve biogas production from PLA digested alone or with FW and paving the way for more sustainable bioplastics and food waste management.