Post-Consumer Poly(ethylene terephthalate) (PET) Depolymerization by Yarrowia lipolytica: A Comparison between Hydrolysis Using Cell-Free Enzymatic Extracts and Microbial Submerged Cultivation

Unveiling potential PET degrading eukaryotes through in silico bioprospecting of PETases

This study addresses the environmental problem of PET plastic through in silico bioprospecting for the identification and experimental validation of novel PET degrading eukaryotes through the in silico bioprospectingI of PETases, employing a methodology that combines Hidden Markov Models (HMMs), clustering techniques, molecular docking, and dynamic simulations. A total of 424 putative PETase sequences were identified from 219 eukaryotic organisms, highlighting six sequences with low affinity energies. The Aspergillus luchuensis sequence showed the lowest Gibbs free energy and exhibited stability at different temperatures in molecular dynamics assays. Experimental validation, through a plate clearance assay and HPLC, confirmed PETase activity in three wild-type fungal strains, with A. luchuensis showing the highest efficiency. The results obtained demonstrate the effectiveness of combining computational and experimental approaches as proof of concept to discover and validate eukaryotes with PET-degrading capabilities opening new perspectives for the sustainable management of this type of waste and contributing to its environmental mitigation.

Exploring yeast biodiversity and process conditions for optimizing ethylene glycol conversion into glycolic acid

Plastics have become an indispensable material in many fields of human activities, with production increasing every year; however, most of the plastic waste is still incinerated or landfilled, and only 10% of the new plastic is recycled even once. Among all plastics, polyethylene terephthalate (PET) is the most produced polyester worldwide; ethylene glycol (EG) is one of the two monomers released by the biorecycling of PET. While most research focuses on bacterial EG metabolism, this work reports the ability of Saccharomyces cerevisiae and nine other common laboratory yeast species not only to consume EG, but also to produce glycolic acid (GA) as the main by-product. A two-step bioconversion of EG to GA by S. cerevisiae was optimized by a design of experiment approach, obtaining 4.51 ± 0.12 g l-1 of GA with a conversion of 94.25 ± 1.74% from 6.21 ± 0.04 g l-1 EG. To improve the titer, screening of yeast biodiversity identified Scheffersomyces stipitis as the best GA producer, obtaining 23.79 ± 1.19 g l-1 of GA (yield 76.68%) in bioreactor fermentation, with a single-step bioprocess. Our findings contribute in laying the ground for EG upcycling strategies with yeasts.