Konstanz researchers identify dual-function 'Pac-Man' enzyme degrading LCAP bioplastics and penicillin in soil metagenomes

Harry Lerner and David Schleheck buried LCAP films ten centimeters deep in botanical-garden humus and ran parallel lab microcosms with powdered polymer. Metagenomic sequencing of the resulting biofilms revealed a single esterase gene whose product, dubbed the Pac-Man enzyme, contains an unusually open catalytic cleft. In vitro assays confirmed rapid chain scission of the polyester and, unexpectedly, cleavage of the beta-lactam ring in penicillin. The one-year field disappearance of the films supplies direct evidence that natural microbial communities can mineralize these engineered materials at scale. The finding connects two previously separate research threads: the plastisphere microbiome and the environmental resistome. Because LCAPs mimic cutin, a plant polyester already abundant in soil, bacteria that already degrade cutin appear pre-adapted to the new substrate. The penicillin activity raises the possibility that selection for plastic-degrading enzymes could enrich beta-lactamase-like folds, a risk that remains unquantified. Routine monitoring of soil resistomes near bioplastic production or composting sites would test whether the overlap is functionally meaningful. Wider adoption of LCAP-type polymers is required before the enzyme can affect global plastic loads; conventional polyolefins lack the ester bonds the enzyme targets. Follow-on work should include directed evolution for higher activity on mixed plastic streams and controlled mesocosm experiments that measure both polymer mass loss and antibiotic-resistance gene abundance simultaneously. Regulatory approval pathways for enzyme-augmented composting facilities will also need data on horizontal gene transfer rates.