Stoichiometric Conversion of Maltose for Biomanufacturing by Synthetic Enzymatic Biosystems.

Maltose is a natural -(1,4)-linked disaccharide with wide applications in food industries and microbial fermentation. However, maltose has scarcely been used for biosynthesis, possibly because its phosphorylation by maltose phosphorylase (MP) yields -glucose 1-phosphate (-G1P) that cannot be utilized by -phosphoglucomutase (-PGM) commonly found in synthetic enzymatic biosystems previously constructed by our group. Herein, we designed an synthetic enzymatic reaction module comprised of MP, -phosphoglucomutase (-PGM), and polyphosphate glucokinase (PPGK) for the stoichiometric conversion of each maltose molecule to two glucose 6-phosphate (G6P) molecules. Based on this synthetic module, we further constructed two synthetic biosystems to produce bioelectricity and fructose 1,6-diphosphate (FDP), respectively. The 14-enzyme biobattery achieved a Faraday efficiency of 96.4% and a maximal power density of 0.6 mW/cm, whereas the 5-enzyme FDP-producing biosystem yielded 187.0 mM FDP from 50 g/L (139 mM) maltose by adopting a fed-batch substrate feeding strategy. Our study not only suggests new application scenarios for maltose but also provides novel strategies for the high-efficient production of bioelectricity and value-added biochemicals.