Efficient synthesis of 5-hydroxytryptophan in Escherichia coli by bifunctional utilization of whey powder as a substrate for cell growth and inducer production.

5-Hydroxytryptophan (5-HTP), a precursor of the neurotransmitter serotonin in mammals, has demonstrated efficacy in treating various diseases such as depression, fibromyalgia and obesity. However, conventional biosynthesis methods of 5-HTP are limited by low yield and high reagent and process costs. In this study, the strain C1T7-S337A/F318Y with optimized promoter distribution was obtained, and the 5-HTP yield was 60.30 % higher than that of the initial strain. An efficient fermentation process for 5-HTP synthesis was developed using strain C1T7-S337A/F318Y with whey powder as a substrate for cell growth and inducer production. Shake flask fermentation experiments yielded 1.302 g/L 5-HTP from 2.0 g/L L-tryptophan (L-Trp), surpassing the whole-cell biocatalysis by 42.86 %. Scale-up to a 5 L fermenter further increased the yield to 1.649 g/L. This fermentation strategy substantially slashed reagent cost by 95.39 %, providing a more economically viable and environmentally sustainable route for industrial biosynthesis of 5-HTP. Moreover, it contributes to the broader utilization of whey powder in various industries.