Sustainable glycolic acid production using Gluconobacter frateurii: Preventing end-product inhibition for efficient upcycling of polyethylene terephthalate

Upcycling of polyethylene terephthalate (PET) has promise for mitigating the environmental burden of plastic waste. This study aimed to evaluate the feasibility of glycolic acid (GA) production by microorganisms using PET-derived ethylene glycol (EG). First, we isolated Gluconobacter frateurii SY6 and developed a mutant strain, G. frateurii SC9, with enhanced GA resistance to address end-product inhibition. Our investigations demonstrated that a resting cell concentration of 15 g/L and an initial EG concentration of 80 g/L led to production of 98.7 g/L of GA in 60 h. To assess the practicality of PET-derived EG for GA bioconversion at fermentor scale, simulated EG was used. GA production was inhibited by NaCl generated during the neutralization of the PET degradation process, and this decreased the yield 18.7% (80.1 g/L). Despite these challenges, G. frateurii SC9 achieved the highest reported fermentor-scale yield of GA from simulated EG, demonstrating its potential for use in industrial-scale upcycling of PET.