Polystyrene Waste Bacteria May Break Down Polyester Say Brunel University Research Team
Image By Courtesy of Brunel University
Scientists have enriched expanded polystyrene waste from a beach in Ireland to isolate a bacterium shown to contain three enzymes that could break down polyester.
The team, from Brunel University London, is studying microorganisms that can degrade plastic, in the hope the microorganisms or their plastic-degrading enzymes can be used to manage the growing plastic waste problem.
Plastic pollution is a growing worldwide problem, with 12,000 million metric tonnes (Mt) of plastic waste predicted to be in the environment and landfill by 2050 (Geyer et al., 2017).
While recycling can give a second life to some plastic, downstream quality and cost can be limiting factors, resulting in only 9% of plastic waste having ever been recycled (Geyer et al., 2017; Shamsuyeva & Endres, 2021).
If plastic is not recycled, it is either sent to landfill where it can pollute the soil and run off pollutes the global water systems, or it is incinerated, potentially releasing toxic fumes, and adding to carbon emissions (Chianga et al., 1992; Jambeck et al., 2015; Li et al., 2001; Royer et al., 2018).
A more environmentally friendly alternative is biodegradation of plastic by microorganisms into non-toxic breakdown products, some of which can be valorised with downstream industrial uses such as succinic acid, which can be used an acidity regulator in the food industry or polyhydroxyalkanoate (PHA), which is a bioplastic (Kenny et al., 2008; Ru et al., 2020).
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Their research paper ‘Enrichment of native plastic‐associated biofilm communities to enhance polyester degrading activity’, is set to publish in Environmental Microbiology.
“If microorganisms can degrade plastic that cannot be recycled, this will reduce the amount of plastic that is incinerated and landfilled,” said corresponding author Dr Ronan McCarthy.
“Many of the known plastic-degrading microorganisms and enzymes have naturally low efficiency, so we need to select for organisms that have higher efficiency or engineer the enzymes to work better. We found that native plastic waste communities can be enriched for communities that have better degradation activity through our enrichment experiment.
“This method can be applied to any waste plastic and the enrichment experiment conditions adapted to optimise isolation of bacteria that are appropriate for industrial batch culture. We also identified three putative enzymes that could be involved in polyester degradation.”
The team collected native bacterial communities from environmental waste plastic and then conducted an enrichment experiment to find communities that had improved plastic degrading abilities after only having the plastic waste as a carbon source.
They observed a change in community composition, and identified a strain of Pseudomonas stutzeri that had three putative enzymes that could have a role in polyester degradation.
Future studies could focus on carrying out the same enrichment experiment on different plastic waste samples to identify new species of bacteria that can degrade different types of plastic.
“It offers a promising way to enrich for species that can thrive on plastic waste. The more bacteria we find that are capable of degrading more diverse plastic, the better options we have for industrial applications of microorganisms to degrade plastic waste,” Dr McCarthy said.
“The three putative enzymes we found will be investigated further to confirm if they are active against polyester. If they are, they could be added to the repertoire of known plastic-degrading enzymes, which could be engineered to have even better activity.”
