Fast Degradation of Polycaprolactone/Poly(butylene adipate- co- terephthalate) Blends by Novel Bacillus Strain NR4 with Broad Degrading Activity

Polycaprolactone (PCL) is a promising biodegradable plastic that has been used, alone or combined with other biopolymers, in many commercial applications. Several studies on microbial-dependent degradation of PCL have been conducted; however, a lesser focus has been placed on the degradation of PCL-polymer blends. We screened PCL-degrading marine bacteria and selected four PCL-degrading strains. Among these, Bacillus sp. NR4 was chosen because it had the greatest clear zone radius, the highest PCL degradation yield, and the highest esterase activity. After culture condition optimization, the PCL-degrading ability of Bacillus sp. NR4 was confirmed using scanning electron microscopy, gel permeation chromatography, and Fourier transform infrared spectroscopy. As a result of gas chromatography–mass spectrometry analysis, Bacillus sp. NR4 had an 85.6% PCL degradation yield after 10 days and possessed degradation ability for other bioplastics, such as poly(butylene adipate- co -terephthalate) (PBAT). Upon studying PCL/PBAT blends, the highest degradation was achieved with a 1:1 ratio after 14 days and degraded by up to 88.3%. This is the first report on the degradation of PCL/PBAT blends by a single strain. Therefore, we expect that Bacillus sp. NR4 can be used for the efficient commercial degradation of PCL and PCL/PBAT blends.