 Petroleum-based plastics have replaced many natural materials, but their high recalcitrance results in long persistence in the environment and growing plastic waste. Microbial enzymes capable of modifying or degrading synthetic polymers are emerging as candidates for biocatalytic plastic recycling processes to recover valuable raw materials in an environmentally sustainable way, with a focus on polyethylene, polystyrene, polyurethane, and PET. Recent progress and challenges in the application of polyester hydrolases for PET building block recovery will be discussed. This article was offered by Ren Wei and Wolfgang Zimmermann.