The special effect of the Aspergillus flavus and its enzymes on biological degradation of the intact polylactic acid (PLA) and PLA-Jute composite

The biodegradation of PLA and PLA-Jute (64/36) in an aqueous media with Aspergillus flavus CCUG 28296, as well as its cell-free enzyme extract, was investigated through their physical, molecular, and thermal characterization. Results indicated that the thicknesses of the fungal treated PLA and PLA-jute samples during seven months have reduced by 52% and 63%, respectively while for the enzyme-treated samples, 45% and 49% reduction in the thickness has occurred. Moreover, the gel permeation chromatography (GPC) revealed a substantial decrease (about 75%) in the weight average molecular weight (Mw) of PLA and PLA-Jute treated with fungus, which confirmed the effective performance of A. flavus on the biological degradation of PLA. The obtained results were further supported by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of the treated and control samples as well. Interestingly, the observed reduction in the Mw of PLA in PLA-Jute was 64% after the enzymatic treatment, while for the unblended PLA, it was just about 32%. These results pointed to the synergistic effect of jute on PLA degradation because of the promiscuous activity of the effective enzymes on jute degradation, which could accelerate the PLA decomposition. (C) 2020 Elsevier Ltd. All rights reserved.