Combination of enzyme engineering and quorum sensing system for efficient de novo biosynthesis of β-arbutin in Escherichia coli

β-Arbutin is a plant-derived glycoside with various biological activities, which has been applied in pharmaceuticals and whitening cosmetics. Uneven carbon flux distribution and the low catalytic efficiency of arbutin synthase limit the biosynthesis of β-arbutin in microorganisms. In addition, commonly used high-cost, or toxic, inducible expression agents are not practical to use in industrial production. In this study, a biosynthetic pathway for β-arbutin was constructed in Escherichia coli. The competition and degradation pathways were knocked out, and the key pathway enzymes were identified and overexpressed, to increase β-arbutin production. Furthermore, by combining modifications to the phosphoketolase pathway and the acetic acid pathway, the carbon flux was redirected to the shikimic acid pathway. The substrate access channel of the arbutin synthase active site was modified by protein engineering, resulting in the R241H mutant, which increased β-arbutin production by 16.7 %, compared with wild type (WT). Finally, the luxR-based quorum sensing (QS) system was used to regulate the allocation of metabolic fluxes between cell growth and product synthesis, achieving a self-induced regulation of E. coli, without requiring exogenous inducers. The final engineered strain produced 81.9 g/L of β-arbutin from a fed-batch fermentation in a 5 L fermenter and the yield from glucose reached 0.29 g/g. This study presents a systematic strategy that can provide a reference for the construction of β-arbutin microbial cell factories.