Characterization of bacterial communities responsible for bioplastics degradation during the thermophilic and the maturation phases of composting

Abstract

Bioplastic waste may play a key role in shaping the microbial communities in composting environment. The present study aims to determine the possible influence of bioplastics on microbial structure of aerobic organic waste treatments and to assess the evolution of microbial community during thermophilic and maturation phases of composting, comparing microorganisms in compost and attached on bioplastics surface. Composting process was simulated in a 2-month lab-scale test. Mater-Bi®, PBAT, PLA and LDPE were considered as benchmark. A qualitative screening was done with DGGE, and then the bacterial community profile was disclosed with 16S rRNA amplicon analysis. The 16S rRNA profile in bioplastics-associated communities was found to largely differed from that of the initial compost (positive control). Moreover, as expected, during the thermophilic phase there was a prevalence of better heat-resistant phyla compared to the mesophilic phase. Some specialists were found to be plastic nature dependent, in particular Streptomyces, Pseudomonas, Aeribacillus, Schlegellela and Cohnella were among the most abundant genera. Finally, to select bacterial species capable of growing on the tested bioplastics, an enrichment method was applied. The method disclosed the possibility to culture some specific bioplastics degrading species, opening the frontiers for bioaugmentation practice in industrial composting.