Degradation of poly(d-lactic acid) by a thermophile

Abstract A thermophile, which was isolated from soil as a microbe degrading poly(butylene succinate- co -butylene adipate) and identified as Bacillus stearothermophilus , was applied to degradation of poly( d -lactic acid) (PDLA) film. In the cultivation at 60 °C, the strain grew on PDLA and the dissolved total organic carbon (TOC) concentration in the medium changed according to the growth stage, i.e., after the TOC rapidly reached the minimum, it increased gradually. As for residual PDLA, gel permeation chromatograms showed a marked shift of the whole peak to low molecular weight region, and moreover, degree of crystallinity increased, while melting temperature decreased. PDLA was proved to be highly degraded by this strain.