Liu Yi, Li Sha, Xu Hong, Wu Lingtian, Xu Zheng, Liu Jing, Feng Xiaohai
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Food Science and Light Industry, Nanjing University of Technology , 30 Puzhu South Road, Nanjing 211816, People's Republic of China.
J Agric Food Chem. 2014 Jul 16;62(28):6756-62. doi: 10.1021/jf501937j. Epub 2014 Jul 8.
D-tagatose, a functional sweetener, is commonly transformed from D-galactose by L-arabinose isomerase (L-AI). In this study, a novel type of biocatalyst, L-AI from Lactobacillus fermentum CGMCC2921 displayed on the spore surface of Bacillus subtilis 168, was developed for producing D-tagatose. The anchored L-AI, exhibiting the relatively high bioactivity, suggested that the surface display system using CotX as the anchoring protein was successfully constructed. The stability of the anchored L-AI was significantly improved. Specifically, the consolidation of thermal stability representing 87% of relative activity was retained even at 80 °C for 30 min, which remarkably favored the production of D-tagatose. Under the optimal conditions, the robust spores can convert 75% D-galactose (100 g/L) into D-tagatose after 24 h, and the conversion rate remained at 56% at the third cycle. Therefore, this biocatalysis system, which could express the target enzyme on the food-grade vector, was an alternative method for the value-added production of D-tagatose.
D-塔格糖是一种功能性甜味剂，通常由L-阿拉伯糖异构酶（L-AI）将D-半乳糖转化而来。在本研究中，开发了一种新型生物催化剂，即展示在枯草芽孢杆菌168孢子表面的来自发酵乳杆菌CGMCC2921的L-AI，用于生产D-塔格糖。锚定的L-AI表现出较高的生物活性，表明以CotX作为锚定蛋白的表面展示系统成功构建。锚定的L-AI的稳定性显著提高。具体而言，即使在80℃下处理30分钟，热稳定性的巩固仍保持相对活性的87%，这对D-塔格糖的生产极为有利。在最佳条件下，健壮的孢子在24小时后可将75%的D-半乳糖（100 g/L）转化为D-塔格糖，在第三个循环时转化率仍保持在56%。因此，这种能够在食品级载体上表达目标酶的生物催化系统是D-塔格糖增值生产的一种替代方法。
