Insights into the Degradability of Poly(lactic acid) and Its Association with the Bacterial Community in a Simulated Industrial Food Waste Composting System

Abstract

The environmental risk associated with bioplastics has garnered increasing attention. However, their fates and the driving mechanisms in industrial composting engineering, which is a primary method for treating food waste, remain unclear. This study delved into the degradation behaviors of poly(lactic acid) (PLA) and its correlation with the PLA-associated bacterial communities in simulated food waste composting systems with and without the addition of a microbial agent (MA). The results derived from the water contact angle and molecular weight (M_n) analyses indicate that composting exhibited a limited degradation capacity for the polymer. The addition of the microbial agent (MA) demonstrated a promoting effect, leading to final M_n values of 8970 g·mol^–1 for the treatment group and 19,324 g·mol^–1 for the control group, compared to an initial M_n of 50,136 g·mol^–1 for the polymer. The influence of composting on PLA-associated bacterial communities manifested in the later stages of composting, showing a lower diversity (Shannon index of 4.11) compared to the compost (4.50). The supplementation of MA facilitated the development of biofilms within the plastisphere, resulting in an increased level of presence of functional bacteria crucial for PLA degradation. This study sheds light on the underlying mechanisms of PLA degradation under typical food waste composting conditions, providing crucial insights into the effective handling and risk evaluation of bioplastics in composting environments.