Enzymatic degradation of polyesters

The constant increase of the plastic production over the world has become a serious problem, since most conventional plastic materials come from fossil resources and are not biodegradable. This causes significant plastics accumulation in the environment, whose end-life must be managed. An effective and eco-friendly approach to solve such problem is the use of biodegradable materials. Biopolymers such as poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate) (PBSA), poly(caprolactone) (PCL), poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) are among the most promising biodegradable commercial polyesters thanks to their high susceptibility to hydrolytic enzymes and to many microorganisms naturally occurring in the environment. The current study is an investigation of the degradation ability of several hydrolytic enzymes (i.e. lipase, esterase, etc.) against some common aliphatic commercial polyesters. The degradation is studied through preliminary film opacity assay, then weight loss measurements were combined to other analyses (i.e., GPC, ¹H NMR, FT-IR, DSC and TGA) performed on the residual solids of polyester films after treatment with the different enzymes, in order to understand molecular and chemical modifications induced at the surface and/or in the bulk of polymer materials over time. The results showed that the enzymatic degradation occurred homogenously from the surface through an erosion mechanism and involved both the amorphous and the crystalline regions. Cleaving action mode for each enzyme (endo- and/or exo-type) is also proposed.