Degradation of biodegradable plastics by anaerobic digestion: Morphological, micro-structural changes and microbial community dynamics

The serious environmental problem caused by traditional plastics has stimulated the popularization of biodegradable plastics (BPs). However, the rigorous prerequisite for the efficient degradation of BPs has not eliminated its potential hazard to nature. In most biosystems exists the anaerobic environment, but it is still controversial whether BPs can be degraded under such condition. Therefore, this study systematically assessed the anaerobic degradation performance of ten common BPs under mesophilic and thermophilic conditions. Results showed that four BPs were degraded evidently under mesophilic condition with the biodegradability of 57.9%-84.6%, while during thermophilic condition, five BPs showed remarkable degradation performance with the biodegradability of 53.0% to 95.7%. According to morphological and micro-structural analysis, the biodegradation of the BPs probably proceeded via bulk and/or surface erosion. Under mesophilic condition, Anaerolineales, Bacteroidales, Clostridiales, SBR1031, and Synergistales appeared to play an important role. During thermophilic condition, the hydrolysis, acidogenesis, and methanogenesis of most BPs were mainly conducted by Coprothermobacter and the archaea Methanothermobacter. This work not only provides crucial data on the anaerobic biodigestibility of BPs but also enriches the understanding of the BPs degradation mechanisms, which are of great importance for future popularization of BP products and simultaneously relieving the environmental pollution.