An artificial multienzyme cascade for the whole-cell synthesis of rare ketoses from glycerol

Abstract

Purpose: In our previous study, we constructed a one-pot multi-enzyme system for rare ketoses synthesis based on L-rhamnulose-1-phosphate aldolase (RhaD) from accessible glycerol in vitro. To eliminate tedious purification of enzymes, a facile Escherichia coli whole-cell cascade platform was established in this study.

Methods: To enhance the conversion rate, the reaction conditions, substrate concentrations and expressions of related enzymes were extensively optimized.

Results: The biosynthetic route for the cascade synthesis of rare ketoses in whole cells was successfully constructed and three rare ketoses including D-allulose, D-sorbose and L-fructose were produced using glycerol and D/L-glyceraldehyde (GA). Under optimized conditions, the conversion rates of rare ketoses were 85.0% and 93.0% using D-GA and L-GA as the receptor, respectively. Furthermore, alditol oxidase (AldO) was introduced to the whole-cell system to generate D-GA from glycerol, and the total production yield of D-sorbose and D-allulose was 8.2 g l^-1 only from the sole carbon source glycerol.

Conclusion: This study demonstrates a feasible and cost-efficient method for rare sugars synthesis and can also be applied to the green synthesis of other value-added chemicals from glycerol.

Keywords: Aldol reaction; Aldolase; Cascade reactions; Rare sugar; Whole cell.