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

초록

Upcycling of polyethylene terephthalate (PET) has emerged as a promising strategy to mitigate the environmental burden of plastic waste. PET can be chemically depolymerized into monomeric components, including ethylene glycol (EG), and effective valorization of PET-derived EG through microbial conversion to glycolic acid (GA) provides an efficient route for PET upcycling. In this study, the feasibility of GA production by microorganisms using PET-derived EG was evaluated. Gluconobacter frateurii SY6 was isolated, and a mutant strain, G. frateurii SC9, with enhanced resistance to GA was developed to mitigate end-product inhibition. Under optimized conditions, a resting cell concentration of 15 g/L and an initial EG concentration of 80 g/L resulted in the production of 98.7 g/L of GA within 60 h. To assess the practicality of PET-derived EG for GA bioconversion at the fermentor scale, simulated EG was used to mimic the chemical conditions of PET-derived EG, particularly the presence of salts generated during neutralization. GA production was inhibited by NaCl generated during the neutralization of the PET degradation process, and this decreased the yield by 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.

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