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Plastic-degrading enzymes found in landfills

Enzymes found in landfills around the world may be able to break down plastic waste. Some 11 billion metric tons of plastic are projected to accumulate in the environment by 2050. Enzymatic and microbial degradation is a promising method of plastic recycling. Landfills, environments where plastics are an abundant resource, are crucibles of bacterial evolution.

Liyan Song and colleagues collected plastic biocatalytic enzymes from landfills around the world, using metagenomics and machine learning. Samples came from China, Italy, Canada, Great Britain, Jamaica, and India and included refuse, leachate, sludge, and airborne particles. The authors identified 31,989 possible plastic-degrading enzymes using the machine learning model CLEAN, which stands for "contrastive learning-enabled enzyme annotation."

The authors then inferred the catalytic activity and microbial hosts of 712 predicted proteins using tertiary structure modeling, superposition, and metagenome-assembled genomes (MAG) reconstruction. The authors recommend further work to confirm the predicted protein functions, noting their versatile capabilities could broaden applications for tackling plastic waste.

According to the authors, plastic may not be forever—and landfill bacteria can help shorten the life of plastic pollution. The paper is in the journal PNAS Nexus.