Abiotic aging assisted bio-oxidation and degradation of LLDPE/LDPE packaging polyethylene film by stimulated enrichment culture

Abstract

Polyethylene (PE), designed to be a packaging film with a short usage life cycle, is dominantly contributing to plastic waste. Here, the preliminary degradation of packaging PE film composed of a blend of LLDPE and LDPE has been investigated. A two-stage process of oxidation, linking abiotic and biotic treatment using enrichment cultures derived from the landfill site of the Deonar dumping ground, was employed to escalate the degradation process. The primary effects of abiotic aging on LLDPE/LDPE film were prominent in natural weathering conditions than thermal aging, resulting in the formation of oxidized functional macromolecules. Further, the enrichment cultures were potentially able to increase the oxidation level of naturally weathered film, detected by increased carbonyl peaks in the ATR-FTIR spectra. Also, the biotic aging concomitantly results in the reduction in water contact angle (WCA), demonstrating the deterioration in the surface property of LLDPE/LDPE film. Additionally, the stimulated enrichment cultures showed a significant variation in oxidation peaks of weathered film. The ATR-FTIR spectrum of the treated film reveals that the glucose-stimulated enrichment cultures (LPG) exhibited increased carbonyl peak intensity whereas yeast extract enrichment cultures (LPYE) showed increased intensity for the –C=C– unsaturated group. A dense biofilm layer with extracellular polymeric substances (EPS) attached to the LLDPE/LDPE surface, as indicated through SEM analysis, confirms microbial growth and utilization of PE material. Further, the bio-oxidation and degradation of LLDPE/LDPE film were verified using Gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis confirms the presence of compounds having short linear hydrocarbon chains with alcohol and ester groups. These results demonstrate the degradation of LLDPE/LDPE packaging PE film in suitable abiotic conditions with emphasis on the enrichment culture's dependability for efficient biotic oxidation. Thus, the approach can be used to develop methods to alleviate the environmental pollution caused by plastic waste.