Searching for new microbial enzymes for plastic polymer degradation: Polyurethanes and Lycra

New enzymes and biocatalysis could provide routes to help limit global plastic pollution, as suggested by the example of PETases for the PET degradation. Experiments were conducted to screen soil microorganisms for enzymes able to break down the plastic polymer Lycra, which contains polyurethane linkages and could be utilized as a carbon and nitrogen source.

The methodology is based on a plate assay, which compared the growth of bacteria at 50°C and 65°C on minimal media and minimal media with a top layer, that contained DMF-dissolved Lycra. The medium provided the main nutrients required for bacterial growth, with Lycra being the only substantial carbon source. Promising candidates were identified as bacterial colonies with visibly enhanced growth on the Lycra-enriched minimal medium plate. The selected soil microorganisms were then tested with a liquid culture assay, where the strain was cultivated at 50°C or 65°C in liquid broth medium, that contained dissolved Lycra. The liquid culture samples were collected at 4 time points between 0-48h, and the aliquots tested on HPLC for detection of released Lycra monomers.

Around 50 different bacterial strains from 6 various soil and compost sources were tested with the described plate screening method and 7 bacterial thermophilic species were detected, that showed visibly enhanced growth on the Lycra-enriched plates. These results could support the development of Lycra enzymatic degradation. New enzymes could be engineered, optimized and yield a sustainable solution for the textile industry, which would not require toxic chemicals or contribute to landfill.