State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing, 210009, People's Republic of China.
Appl Biochem Biotechnol. 2012 Feb;166(4):961-73. doi: 10.1007/s12010-011-9484-8. Epub 2011 Dec 28.
D-tagatose is a ketohexose that can be used as a novel functional sweetener in foods, beverages, and dietary supplements. This study was aimed at developing a high-yielding D-tagatose production process using alginate immobilized Lactobacillus fermentum CGMCC2921 cells. For the isomerization from D-galactose into D-tagatose, the immobilized cells showed optimum temperature and pH at 65 °C and 6.5, respectively. The alginate beads exhibited a good stability after glutaraldehyde treatment and retained 90% of the enzyme activity after eight cycles (192 h at 65 °C) of batch conversion. The addition of borate with a molar ratio of 1.0 to D-galactose led to a significant enhancement in the D-tagatose yield. Using commercial β-galactosidase and immobilized L. fermentum cells, D-tagatose was successfully obtained from lactose after a two-step biotransformation. The relatively high conversion rate and productivity from D-galactose to D-tagatose of 60% and 11.1 g l⁻¹ h⁻¹ were achieved in a packed-bed bioreactor. Moreover, lactobacilli have been approved as generally recognized as safe organisms, which makes this L. fermentum strain an attracting substitute for recombinant Escherichia coli cells among D-tagatose production progresses.
D-塔格糖是一种酮己糖，可用作食品、饮料和膳食补充剂中的新型功能性甜味剂。本研究旨在利用海藻酸钠固定化乳杆菌 CGMCC2921 细胞开发高产 D-塔格糖的生产工艺。对于 D-半乳糖向 D-塔格糖的异构化，固定化细胞的最佳温度和 pH 值分别为 65°C 和 6.5。经过戊二醛处理后，海藻酸钠珠表现出良好的稳定性，在 65°C 下连续 8 个批次（192 h）转化后保留了 90%的酶活性。向 D-半乳糖中添加摩尔比为 1.0 的硼酸盐可显著提高 D-塔格糖的产量。使用商业β-半乳糖苷酶和固定化乳杆菌细胞，可从乳糖成功获得 D-塔格糖。在填充床生物反应器中，D-半乳糖到 D-塔格糖的相对较高转化率和产率分别达到 60%和 11.1 g·l⁻¹·h⁻¹。此外，乳杆菌已被批准为一般公认安全的生物体，这使得该乳杆菌菌株成为 D-塔格糖生产过程中重组大肠杆菌细胞的有吸引力的替代品。
