Technological watch

ABSTRACTRecently, microbial fermentation for the synthesis of rare sugars has garnered considerable attention. d?Allose, a rare monosaccharide, has emerged as a significant bioproduct in the food and pharmaceutical industries due to its unique health benefits and physiological functions. However, the detection of d?allose in fermentation broth samples predominantly depends on complex chromatographic techniques. This study introduces a toggle?programmed microbial fluorescent biosensor designed for the dynamic monitoring of d?allose. The d?allose?sensing PalsR promoter, located within the alsRBACEK operon, was initially characterized and used as a core component in the biosensor. The native PT7 promoter and the PalsR promoter were then utilized for the expression of green fluorescent protein (GFP) and T7 RNA polymerase (T7 RNAP), respectively. The constitutive Ppdc promoter was employed to overexpress the repressor protein AlsR in the cytoplasm, thereby ensuring effective regulation of PalsR. More importantly, a fast?folding and fast?degrading mGFP?DAS replaced GFP as the reporter, facilitating a rapid response to d?allose during continuous microbial incubation. The results demonstrated that this novel biosensor exhibited high sensitivity to d?allose levels, with measurement deviation controlled within 15%. This approach offers significant advantages over traditional d?allose chromatography detection methods, particularly in terms of simplicity and cost?effectiveness.