Enzymatic hydrolysis of microcrystalline cellulose for efficient and economic production of astragalin in metabolic engineering of Escherichia coli

Abstract

Cellulose is the most abundant biomass in nature, and the development of high-value utilization technologies for cellulose is of great significance. In this work, a recombinant strain was engineered by introducing Arabidopsis thaliana glycosyltransferase (AtUGT78D2) and the cellobiose phosphorolysis route to produce astragalin from kaempferol. By optimizing the transformation conditions, the production of astragalin increased from 1053 to 3031 mg/L with the addition of cellobiose. Subsequently, the cellulose enzymatic solution was used to replace cellobiose as the carbon source and UDP-glucose precursor for producing astragalin. By optimizing enzymatic conditions and adding additives, the concentration of cellobiose significantly increased, resulting in an increase in the production of astragalin to 2279 mg/L. The adsorption strategy was employed to modulate the composition and activity of cellulase, and the ratio of cellobiose to glucose in the cellulose enzymatic solution increased from 0.73 to 1.62, with the yield of cellobiose reaching up to 5.9 g/L. Finally, the highest production of astragalin in the recombinant strain reached 2654 mg/L when the optimal ratio of cellobiose to glucose was used as the carbon source. This study provides a novel method for producing astragalin by using the enzymatic hydrolysis of microcrystalline cellulose.