Integrated self-assembling multi-enzyme display platform on Candida tropicalis surface for efficient degradation of PET waste.

The bioprocess of recycling polyethylene terephthalate (PET) has been extensively studied; however, challenges remain due to its process complexity, low enzymatic performance, and high costs. Here, we devised a strategy termed the Integrated Self-Assembling Multi-Enzyme Display Platform (ISA-MEDP) to directly and efficiently degrade postconsumer PET (pc-PET). We developed a novel surface display system for the unconventional and robust yeast Candida tropicalis, enabling FAST-PETase and MHETase to be functionally anchored onto the cell wall. Based on this display system and the SpyTag-SpyCatcher system, the ISA-MEDP was constructed through the regulation of PETase and MHETase, which were co-displayed on the cell surface at an optimal ratio, as well as the optimization of the self-assembling chronological sequence. The ISA-MEDP significantly enhanced the degradation of untreated pc-PET with crystallinity > 10 % under near-environmental temperatures. In a 5-L bioreactor scale evaluation, 20 g of pc-PET powder was completely depolymerized during a 7-day batch incubation process with only pH control. This study presents a novel and practical platform for the co-display and assembly of enzymes. More importantly, it offers a long-term stable enzyme catalyst for the large-scale depolymerization of PET, which is of substantial significance for related industrial applications.