Weber Nathanael, Lutz-Wahl Sabine, Fischer Lutz
Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, University of Hohenheim, Garbenstr. 25, 70599 Stuttgart, Germany.
J Agric Food Chem. 2025 Jun 25;73(25):15889-15899. doi: 10.1021/acs.jafc.5c04545. Epub 2025 Jun 12.
The sweetness of dairy byproducts can be increased by hydrolysis of lactose to d-glucose and d-galactose and subsequent isomerization to d-fructose and d-tagatose. The isomerization of d-galactose to d-tagatose in skim milk ultrafiltration permeate at pH 4.5 and 6.5 was investigated here, comparing the l-arabinose isomerase from (l-AI-Lp) with l-AI-N13, a protein-engineered variant of l-AI from . l-AI-Lp combined with a commercial β-galactosidase and xylose isomerase converted 95 g/L of lactose to d-glucose, d-galactose, d-fructose, and d-tagatose (23-24 g/L each) at pH 6.5. At pH 4.5, lactose (100 g/L) was converted by a commercial β-galactosidase and l-AI-Lp to 46 g/L d-glucose, 22 g/L d-galactose, and 23 g/L d-tagatose, while no activity was measured for l-AI-N13 at this pH. This is the first study that demonstrates the enzymatic conversion of lactose in a dairy byproduct to d-glucose, d-galactose, and d-tagatose at an acidic pH.
通过将乳糖水解为d-葡萄糖和d-半乳糖，随后异构化为d-果糖和d-塔格糖，可以提高乳制品副产物的甜度。本文研究了脱脂牛奶超滤透过液中d-半乳糖在pH 4.5和6.5条件下异构化为d-塔格糖的过程，将来自[具体来源]的l-阿拉伯糖异构酶（l-AI-Lp）与来自[具体来源]的l-AI的蛋白质工程变体l-AI-N13进行了比较。在pH 6.5条件下，l-AI-Lp与商业β-半乳糖苷酶和木糖异构酶结合，将95 g/L的乳糖转化为d-葡萄糖、d-半乳糖、d-果糖和d-塔格糖（各23 - 24 g/L）。在pH 4.5时，商业β-半乳糖苷酶和l-AI-Lp将100 g/L的乳糖转化为46 g/L的d-葡萄糖、22 g/L的d-半乳糖和23 g/L的d-塔格糖，而在此pH下未检测到l-AI-N13的活性。这是第一项证明在酸性pH条件下将乳制品副产物中的乳糖酶促转化为d-葡萄糖、d-半乳糖和d-塔格糖的研究。
