Improving techno-economics of bioproduct glycolic acid by successive recycled-cell catalysis of ethylene glycol with Gluconobacter oxydans

Bioconversion of ethylene glycol (EG) to glycolic acid (GA) by the whole-cell of Gluconobacter oxydans in an aired stirred tank reactor (ASTR) with continuous substrate feeding yielded over 220 g/L of GA. However, the bioreactor productivity declined to an unfavorable level of 0.63 g/L/h due to negative feed-back by GA which inhibited the reaction. To overcome this problem, based on results obtained from techno-economic comparative analysis, we set up a successive recycled-cell catalytic bioprocessing ASTR, and carried out five consecutive cycles stably during 240 h. At the end of this process, total 490.7 g GA was accumulated with over 90% yield, and an average bioreactor productivity of 2.04 g/L/h. The twin strategies of end-product titer control and cell-recycling successfully demonstrated the large scale applicability of EG bioconversion to GA.