The enzymatic degradation of polycaprolactone (PCL) using lipases obtained from different microorganisms was investigated by measuring weight loss and total organic carbon (TOC) concentration. Lipase from Pseudomonas sp. was able to degrade PCL most efficiently. In this study, three major variables, enzyme concentration, substrate concentration, and reaction time, were optimized to enhance biodegradation of PCL. The optimal condition of biodegradation of PCL was acheived at a substrate concentration of 30 g/L, and enzyme concentration of 30 mg/L, and a degradation time of 15-20 hours. Three different forms of PCL, film, fine powder, and coarse powder, were investigated to understand the effect of surface area on the degradation rate. PCL with large surface area (fine powder) was degraded most efficiently by lipase obtained from Pseudomonas sp.
The ASTM G21-70 method was employed to test biodegradability of PCL compared to polythylene terephthalate (PET) by growing Aspergillus miger on salt-agar plate containing these polymers as the sole carbon sources. The amount of polymers degraded by fungi was monitored by photograph or scanning electron microscopy (SEM). The growth of A niger was apparent on the PCL containing plate, but no growth was observed on PET containing plate. Degradation of PCL due to fungal growth was verified by SEM, which clearly shows physical changes on the PCL film surface. In short, PCL was totally biodegraded by the ASTM method, while PET was not.
The biodegradation of PCL and PET films under soil burial conditions extending up to 3 months has been investigated. SEM pictures of the surface of the soil-buried samples do not reveal the extent of the microbial attack.