Anaerobic Microbial Degradation of Polypropylene and Polyvinyl Chloride Samples

-Resistance to biodegradation, which is among the most advantageous features of synthetic polymers, is also the reason for their accumulation in the environment and therefore pollution. While some type of plastics are known to undergo slow microbial degradation under oxic conditions, the information on the anaerobic degradation of plastics is scarce. In this work, we studied the growth of anaerobic moderately thermophilic (55 degrees C) consortia in the presence of samples made of polypropylene (PP) and polyvinyl chloride (PVC). It was shown that microbial biomass increased compared to the control, and the products of anaerobic decomposition (CO2, H-2, and H2S) were detected, while the total weight of the plastics decreased by 4.4% (PP) and 6.5% (PVC) compared to the control. Bacterial cells adhered to the plastic materials and formed colonies and biofilms on their surface. Analysis of the composition of microbial communities showed an increased number of anaerobic hydrolytics of the genus Tepidimicrobium, potential syntrophic bacteria of the genus Tepidanaerobacter, and especially of sulfate-reducing bacteria (Desulfohalotomaculum). Differential scanning calorimetry and Fourier spectroscopy revealed that the decrease in the mass of plastic occurred mainly due to hydrolysis of the additives (plasticizers), although changes in the plastic structure were also observed for PVC samples. The role of such anaerobic microbial communities in aquatic environments and in deep layers of the municipal solid waste landfills, where PP and PVC plastics may be degraded under the elevated temperatures and anoxic conditions, is discussed.