Abstract：
Galactitol, a rare sugar alcohol, has promising potential in the food industry and pharmaceutical field. The available industrial production methods rely on harsh hydrogenation processes, which incur high costs and environmental concerns. It is urgent to develop environmentally friendly and efficient biosynthesis technologies. In this study, a xylose reductase named AnXR derived from Aspergillus niger CBS 513.88 was identified and characterized for the enzymatic properties. AnXR exhibited the highest activity at 25 ℃ and pH 8.0, and it belonged to the NADPH-dependent aldose reductase family. To engineer a strain for galactitol production, we deleted the galactokinase (GAL1) gene in Saccharomyes cerevisiae by using the recombinant gene technology, which significantly reduced the metabolic utilization of D-galactose by host cells. Subsequently, we introduced the gene encoding AnXR into this modified strain, creating an engineered strain capable of catalyzing the conversion of D-galactose into galactitol. Furthermore, we optimized the whole-cell catalysis conditions for the engineered strain, which achieved a maximum galactitol yield of 12.10 g/L. Finally, we tested the reduction ability of the strain for other monosaccharides and discovered that it could produce functional sugar alcohols such as xylitol and arabinitol. The engineered strain demonstrates efficient biotransformation capabilities for galactitol and other functional sugar alcohols, representing a significant advancement in environmentally sustainable production practices.
摘要：
半乳糖醇,一种稀有的糖醇，在食品工业和制药领域具有广阔的潜力。可用的工业生产方法依赖于苛刻的加氢工艺，这会带来高昂的成本和环境问题。开发环境友好、高效的生物合成技术刻不容缓。在这项研究中,鉴定并表征了源自黑曲霉CBS513.88的名为AnXR的木糖还原酶的酶学性质。AnXR在25℃和pH8.0时表现出最高的活性，属于NADPH依赖性醛糖还原酶家族。为了制造一种生产半乳糖醇的菌株，我们通过重组基因技术删除了酿酒酵母中的半乳糖激酶（GAL1）基因，显著降低了宿主细胞对D-半乳糖的代谢利用率。随后，我们将编码AnXR的基因引入到这个修饰的菌株中，产生能够催化D-半乳糖转化为半乳糖醇的工程菌株。此外，我们优化了工程菌株的全细胞催化条件，最大半乳糖醇产量为12.10g/L。最后,我们测试了该菌株对其他单糖的还原能力，发现它可以产生功能性糖醇，如木糖醇和阿拉伯糖醇。工程菌株展示了半乳糖醇和其他功能糖醇的有效生物转化能力，代表了环境可持续生产实践的重大进步。
