Exploring the potential of thermally degraded polyethene waste for P(3HB-co-3HV) biosynthesis from unreported species of Cupriavidus oxalaticus USM2A2

Abstract

The excessive use of non-biodegradable polyethene (PE) contributes significantly to environmental pollution due to its persistence and accumulation in the environment. This study explores the utilisation of thermally degraded polyethene plastic waste (PEPW) into biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] using a novel strain, Cupriavidus oxalaticus USM2A2, isolated from oil-contaminated sites in Malaysia. Genomic analysis identified this strain as a previously unreported polyhydroxyalkanoate (PHA) producer. Cultivation on low-density polyethene (LDPE) waste pyrolysis oil, co-supplemented with 1-pentanol, resulted in a PHA content of 32 wt% with a 3-hydroxyvalerate (3HV) content of 77 mol%. Optimization of medium conditions using response surface methodology with nonanoic acid as a 3HV precursor, ammonium chloride as a nitrogen source, and yeast extract as a complex nitrogen source improved growth up to 1.0 g/L with 32 wt% PHA content and varying 3HV monomer composition. The genome of C. oxalaticus USM2A2 contains three putative copies of phaC genes, encoding PHA synthase, and a putative cytochrome P450 with monooxygenase activity, suggesting its ability to utilize thermally degraded PEPW substrates. These findings demonstrate the potential of C. oxalaticus USM2A2 to convert PEPW into biodegradable PHA, highlighting the role of microbial PHAs as sustainable alternatives to conventional plastics, addressing environmental pollution and promoting sustainability.

Keywords: Bioconversion; Circular economy; Cupriavidus oxalaticus; P(3HB-co-3HV); Polyethene; Pyrolysis; Thermal degradation.