Enhanced Anaerobic Biodegradation and Biomethane Production from Bioplastics by the Addition of Aerobically Prepared Triacylglycerol Lipase

Abstract

This study aimed to overcome the limited biodegradability of bioplastics under anaerobic conditions. With polycaprolactone (PCL) as a model system, the effect of a bioplastic-degrading enzyme, triacylglycerol lipase (TGL), on its degradation and biomethane production was investigated. As the PCL film did not show evidence of any degradation over 14 days under anaerobic conditions in the sludge, TGL from Bacillus sp. JY35 was added to promote PCL breakdown into its monomeric form, which could be used for methane production. Application of 200 units/mg of TGL in the sludge led to a 33% increase in PCL degradation over 7 days, with sustained lipase activity despite the decreasing trend in effectiveness after 72 h. Across all type of samples, methane production in the TGL-supplemented sludge increased 1.8-fold across sludge types and up to 2.2-fold when bioplastics other than PCL underwent degradation, compared with that in the untreated sludge. Our result showed the addition of concentrated enzyme could effectively improve bioplastics biodegradability concomitant with methane production under anaerobic conditions, thus offering a feasible approach for optimizing anaerobic degradation with various bioplastics such as Polybuthylene succinate (PBS), and Polybutylene adipate-co-terephthalate (PBAT) although it will take longer time than PCL.

Keywords: Anaerobic degradation; biomethane; enzymatic treatment; polycaprolactone; sludge; triacylglycerol lipase.