Biodegradation of poly (vinyl alcohol) by an orychophragmus rhizosphere-associated fungus Penicillium brevicompactum OVR-5, and its proposed PVA biodegradation pathway.

Abstract

In recent years, the utilisation of endophytes has emerged as a promising biological treatment technology for the degradation of plastic wastes such as biodegradation of synthetic plastics. This study, therefore, aimed to explore and extensively screen endophytic fungi (from selected plants) for efficient in vitro polyvinyl alcohol (PVA) biodegradation. In total, 76 endophytic fungi were isolated and cultivated on a PVA screening agar medium. Among these fungi, 10 isolates showed potential and were subsequently identified based on phenotypical characteristics, ITS ribosomal gene sequences, and phylogenetic analyses. Four strains exhibited a maximum level of PVA-degradation in the liquid medium when cultivated for 10days at 28°C and 150rpm. These strains showed varied PVA removal rates of 81% (Penicillium brevicompactum OVR-5), 67% (Talaromyces verruculosus PRL-2), 52% (P. polonicum BJL-9), and 41% (Aspergillus tubingensis BJR-6) respectively. The most promising PVA biodegradation isolate 'OVR-5', with an optimal pH at 7.0 and optimal temperature at 30°C, produced lipase, manganese peroxidase, and laccase enzymes. Based on analyses of its metabolic intermediates, as identified with GC-MS, we proposed the potential PVA degradation pathway of OVR-5. Biodegradation results were confirmed through scanning electron microscopy and Fourier transform infrared spectroscopy. This study provides the first report on an endophytic P. brevicompactum strain (associated with Orychophragmus violaceus) that has a great ability for PVA degradation providing more insight on potential fungus-based applications in plastic waste degradation.