Abstract
D-Allulose has many health-benefiting properties, physiological
functions, and sustainable applications 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 have been reported in this field, but still suffer from
by-product formation and costly purified enzyme involvement. In the
present study, we explored the glycerol assimilation, alditol oxidase,
alcohol dehydrogenase, aldolase, and dephosphorylation pathways, and
modularly designed, assembled, and optimized 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 D-allulose was produced with a molar yield of 31.43%. This study
provided a facile approach to produce D-allulose from glycerol
feedstock.