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Recovery of polyhydroxyalkanoate from the newly identified strain Enterobacter sp. MPLSI-2 isolated from a plastic waste landfill
Summary
Scientists discovered a new bacterial strain, living in a plastic waste dump, of all places, that can turn simple sugar (or even cheap sugarcane byproduct) into a biodegradable plastic-like material. This matters because everyday plastics build up in our environment and break down into microplastics that we breathe, eat, and drink, so finding cheaper, more efficient ways to make truly biodegradable alternatives could help reduce that long-term exposure. This is still early-stage lab research, but it points to a promising, low-cost path toward greener plastics.
Synthetic plastic waste poses a severe environmental threat due to its persistence and accumulation. As a result, producing biodegradable alternatives like polyhydroxyalkanoates (PHAs) is essential to replace conventional plastics and mitigate this pollution crisis. We isolated a novel Enterobacter sp. (MPLSI-2, PV029923) from a plastic waste landfill, a stress-rich and underexplored niche for identifying PHA producers. This study reports the first bioproduction of a novel seven-monomer medium- and long-chain copolymer, P(3HHxD-co-3HHxDe-co-3HOD-co-3HODe-co-3HTeD-co-3HTrD-co-3HHeD), by Enterobacter sp. MPLSI-2. Notably, the complex PHA was synthesized directly from glucose as the sole carbon source. The isolate identified via 16S rRNA sequencing as Enterobacter sp. MPLSI-2 (GenBank accession number: PV029923). Phylogenetic analysis and nucleotide homology confirmed the strain shares 99.44% sequence similarity with Enterobacter bugandensis EB-247 (FYBI01000003). The isolate is a Gram-negative, non-spore-forming rod, positive for citrate utilization and for amylase and protease production. Initial screening using Sudan Black B, Nile Blue A, and PHA-selective media revealed intracellular PHA granules, which were confirmed by microscopic observation. Using a One-Factor-At-A-Time (OFAT) design, culture conditions (temperature, pH) and carbon sources were optimized. Maximum PHA accumulation occurred at 37 °C and pH 7 using glucose (52.1 ± 1.87% DCW), followed by molasses (37.9 ± 0.66% DCW). The achieved productivity highlights the viability of molasses as an alternative substrate. Among recovery methods tested, SDS pretreatment followed by solvent extraction gave the highest extraction yield (74.7 ± 3.72%). While FTIR analysis suggested the characteristic ester carbonyl and alkyl bands indicative of PHAs, complementary GC–MS profiling definitively identified the polymer as a complex seven-monomer copolymer consisting of P(3HHxD-co-3HHxDe-co-3HOD-co-3HODe-co-3HTeD-co-3HTrD-co-3HHeD). These results indicate that Enterobacter sp. MPLSI-2 can produce substantial PHA from both pure and agro-industrial substrates and that optimized recovery improves overall yield.