Microbial degradation of low-density polyethylene and synthesis of polyhydroxyalkanoate polymers

Abstract

We have characterized the ability of eight bacterial strains to utilize powdered low-density polyethylene (LDPE) plastic (untreated and without any additives) as a sole carbon source. Cell mass production on LDPE-containing medium after 21 days of incubation varied between 0.083 ± 0.015 g/L cell dry mass (cdm) for Micrococcus luteus IRN20 and 0.39 ± 0.036 g/L for Cupriavidus necator H16. The percent decrease in LDPE mass ranged from 18.9% ± 0.72% for M. luteus IRN20 to 33.7% ± 1.2% for C. necator H16. Linear alkane hydrolysis products from LDPE degradation were detected in the culture media, and the carbon chain lengths of the hydrolysis products detected varied, depending on the species of bacteria. We also determined that C. necator H16 produced short-chain-length polyhydroxyalkanoate biopolymers, while Pseudomonas putida LS46 and Acinetobacter pittii IRN19 produced medium-chain-length biopolymers while growing on polyethylene powder. Cupriavidus necator H16 accumulated poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-V) polymers to 3.18% ± 0.4% of cdm. The monomer composition of the PHB-V was 94.9% ± 0.61% 3-hydroxybutyrate and 5.03% ± 0.56% 3-hydroxyvalerate. This is the first report that provides direct evidence for simultaneous bioconversion of LDPE plastic to biodegradable polyhydroxyalkanoate polymers.