Abstract：
D-tagatose holds significant importance as a functional monosaccharide with diverse applications in food, medicine, and other fields. This study aimed to explore the oxidoreductive pathway for D-tagatose production, surpassing the contemporary isomerization-mediated biosynthesis approach in order to enhance the thermodynamic equilibrium of the reactions. Initially, a novel galactitol dehydrogenase was discovered through biochemical and bioinformatics analyses. By co-expressing the galactitol dehydrogenase and xylose reductase, the oxidoreductive pathway for D-tagatose synthesis was successfully established in Bacillus subtilis. Subsequently, pathway fine-tuning was achieved via promoter regulation and dehydrogenase-mediated cofactor regeneration, resulting in 6.75-fold higher D-tagatose compared to that produced by the strain containing the unmodified promoter. Finally, optimization of fermentation conditions and medium composition produced 39.57 g/L D-tagatose in a fed-batch experiment, with a productivity of 0.33 g/L/h and a yield of 0.55 mol/mol D-galactose. These findings highlight the potential of the constructed redox pathway as an effective approach for D-tagatose production.
摘要：
D-塔格糖作为功能性单糖具有重要意义，在食品中具有多种应用，医学,和其他领域。本研究旨在探索D-塔格糖生产的氧化还原途径,超越当代异构化介导的生物合成方法，以增强反应的热力学平衡。最初，通过生化和生物信息学分析发现了一种新的半乳糖醇脱氢酶。通过共表达半乳糖醇脱氢酶和木糖还原酶，在枯草芽孢杆菌中成功建立了D-塔格糖合成的氧化还原途径。随后，途径微调是通过启动子调节和脱氢酶介导的辅因子再生，导致与含有未修饰启动子的菌株产生的D-塔格糖相比高6.75倍。最后,发酵条件和培养基组成的优化在分批补料实验中产生39.57g/L的D-塔格糖，产率为0.33g/L/h,产率为0.55mol/molD-半乳糖。这些发现突出了构建的氧化还原途径作为D-塔格糖生产的有效方法的潜力。
