Engineering an efficient whole-cell catalyst for d-allulose production from glycerol

d-Allulose has many health-benefiting properties and therefore sustainably applied in food, pharmaceutical, and nutrition industries. The aldol reaction-based route is a very promising alternative to Izumoring strategy in d-allulose production. Remarkable studies reported in the past cannot get rid of by-product formation and costly purified enzyme usage. In the present study, we explored the glycerol assimilation by modularly assembling the d-allulose synthetic cascade in Escherichia coli envelop. We achieved an efficient whole-cell catalyst that produces only d-allulose from cheap glycerol feedstock, eliminating the involvement of purified enzymes. Detailed process optimization improved the d-allulose titer by 1500.00%. Finally, the production was validated in 3-L scale using a 5-L fermenter, and 5.67 g L^-1 d-allulose was produced with a molar yield of 31.43%.