A research team at Brunel University London has used genomic mining to synthesise eight novel enzymes with the potential to degrade PET. Two of the newly created enzymes were indeed confirmed to actually do so, according to the study published by the team in the journal, Biofilms and Microbiomes.
Enzymes have long been seen as a promising solution to help tackle the waste crisis, with scientists pinpointing several new species that encode enzymes that can degrade plastic. But these enzymes degrade plastic too slowly to be useful. Their efficiency is below what would be required for real world plastic bioremediation applications, Much research is now being directed at improving the efficiency of these enzymes, so they can be more suitable for commercial application.
Synthetic biology uses ideas from engineering to design new biological pathways, organisms and devices and to modify ones found in nature. In this fresh study, they use the techniques to boost bacteria’s abilities to grow in communities called biofilms. Biofilms form on many natural surfaces like soil, water and rocks. In health settings, bacterial infections such as MRSA can form biofilms that create a barrier to antibiotics and the immune system. Natural biofilm formation on plastic has been linked with good plastic degradation, suggesting this may be a behaviour that has also evolved in marine microbial ecosystems contaminated with plastic.
“These new findings are really exciting,” said corresponding author of the study, Dr Ronan McCarthy, Reader in biomedical sciences at Brunel. “Not only have we identified two new PET degrading enzymes, but we found a way to improve their degradation abilities by modifying the bacteria as whole, rather than modifying each enzyme individually.”
The researchers hypothesised that enhancing the ability of the bacteria to attach to and form a biofilm on plastic could increase the local concentration of the enzyme around the target substrate.The biofilm would also reduce the amount of enzyme washed away in the culture. By trapping, as it were, the enzymes in the biofilm matrix, ramping up the concentration of enzymes around the plastic by keeping them in that location longer, the overall rate of plastic degradation increased.
“This suggests that modulating biofilm formation may be an effective strategy to increase the efficiency of plastic degrading bacteria,” said Dr McCarthy. “Using biofilm to enhance plastic degrading enzyme activity could potentially be applied to all plastic degrading enzymes currently in development.”
The team now plan to test the two new enzymes in a bioreactor. “We want to see if increasing biofilm formation improves the degradation of plastic in a more industrial-like setting,” added researcher Dr Sophie Howard. “We also aim to further harness synthetic biology to give even greater control over biofilm formation.”
Modulating biofilm can potentiate activity of novel plastic-degrading enzymes is published in Biofilms and Microbiomes.