Acetate co-feeding increases ethylene glycol assimilation and glycolic acid production in Yarrowia lipolytica

Upcycling ethylene glycol (EG) and terephthalic acid (TPA), key monomers derived from the depolymerisation of polyethylene terephthalate (PET), is a promising strategy for advancing the circular economy of plastics. This study investigates the metabolic fate of EG and its conversion into glycolic acid (GA) by the non-conventional yeast Yarrowia lipolytica. While EG alone does not support growth in a minimal medium, the addition of acetate (Ac) significantly enhances EG assimilation and GA production. ¹³C labeling experiments and metabolic flux analysis revealed that a small but measurable fraction of EG-derived carbon is incorporated into biomass via glycine and serine biosynthesis and the glyoxylate cycle when acetate is supplied as a carbon source. Ac-EG co-feeding resulted in the production of 48.4 ± 1.4 g/L of GA after 66 h, corresponding to a molar yield of 73 % and a productivity of 0.73 g/(L·h). These results highlight the potential of Y. lipolytica as a microbial platform for EG valorisation and contribute to sustainable strategies for the bioconversion of plastic waste.