Pathway prediction of LDPE degradation using Winogradsky column and bacterial strains from municipal solid wastes

Abstract

Plastic waste, considered a great threat to the environment, requires an effective treatment process. The ability of the microbes to oxidize the polymeric chain (C–C bonds), hydrolyze and produce carbon dioxide and water as final products of degradation was studied. The process becomes complicated due to structural complexity of the polymer. The present study is the continuation of the LDPE degradation using the Winogradsky Column. The determination of metabolites formed on degradation is discussed. The FTIR analysis indicated the reduction in the intensity of the C-H, confirming the cleavage of the alkane chains in LDPE. The metabolites produced during the degradation resulted in the formation of smaller alkanes, which contain C32, C22, C16, C18 and aromatic compounds such as phenols and benzene dicarboxylic acid. The occurrence of terminal oxidation of the polymeric chain, cleavage, fragmentation and cyclization of the alkanes confirm the biodegradation process. The current research also focuses on the biodegradation of LDPE using bacterial strains isolated from dumpsite soil samples. The degraded LDPE was analyzed for its metabolite production using GC–MS. It enabled us to understand and hypothesize an overview pathway of LDPE degradation by bacterial strains. The hypothesized pathway indicated that bacterial strains performed fragmentation and cyclization of the long polymeric chain, followed by hydrogenation and oxidation, resulting in the formation of alcohols, aldehydes, ketones and carboxylic acid compounds leading to ester formation. The esters are then understood to enter the ꞵ-oxidation pathway or TCA cycle, producing carbon dioxide and water molecules.