Directed Evolution of Multimodal Plastic Degrading Enzymes

A directed-evolution approach in Escherichia coli produced a multimodal plastic-degrading enzyme mutant that retained polyesterase activity while gaining polyurethane-degrading activity.

• Why it matters: Existing polyester-degrading enzymes are limited to primary substrates and closely related plastics, blocking broader plastic breakdown needed for sustainability.
• What they did: A periplasm-secretable polyesterase was engineered, four active-site positions were randomized to build a >300,000-member library, and plate-based screening plus liquid spectroscopic assays identified active variants.
• The result: One mutant showed new polyurethane-degrading activity on polyurethane-containing agar while retaining polyesterase activity, with computational analysis suggesting an expanded substrate pocket while keeping catalytic residues positioned.