Zhang Guoyan, An Yingfeng, Zabed Hossain M, Yun Junhua, Parvez Amreesh, Zhao Mei, Zhang Cunsheng, Ravikumar Yuvaraj, Li Jia, Qi Xianghui
School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu, China.
College of Biosciences and Biotechnology, Shenyang Agricultural University, 120 Dongling Road, Shenyang 110161, Liaoning, China.
Bioresour Technol. 2023 Dec;389:129843. doi: 10.1016/j.biortech.2023.129843. Epub 2023 Oct 10.
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.
D-塔格糖作为一种功能性单糖，在食品、医药和其他领域有着广泛的应用，具有重要意义。本研究旨在探索D-塔格糖的氧化还原生产途径，超越当代异构化介导的生物合成方法，以提高反应的热力学平衡。最初，通过生化和生物信息学分析发现了一种新型半乳糖醇脱氢酶。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，通过启动子调控和脱氢酶介导的辅因子再生实现了途径微调，与含有未修饰启动子的菌株相比，D-塔格糖产量提高了6.75倍。最后，通过优化发酵条件和培养基组成，在补料分批实验中生产出39.57 g/L的D-塔格糖，生产率为0.33 g/L/h，产率为0.55 mol/mol D-半乳糖。这些发现突出了构建的氧化还原途径作为D-塔格糖生产有效方法的潜力。
