Zhang Wenli, Xiong Suchun, Ni Dawei, Huang Zhaolin, Ding Junmei, Mu Wanmeng
State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu 214122, China.
State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu 214122, China; Engineering Research Center of Sustainable Development and Utilization of Biomass Energy, Ministry of Education, Yunnan Normal University, Kunming 650500, China.
Int J Biol Macromol. 2024 Jun;271(Pt 1):132478. doi: 10.1016/j.ijbiomac.2024.132478. Epub 2024 May 19.
Bioconversion of lactose to functional lactose derivatives attracts increasing attention. Lactulose is an important high-value lactose derivative, which has been widely used in pharmaceutical, nutraceutical, and food industries. Lactulose can be enzymatically produced from lactose by cellobiose 2-epimerase (CEase). Several studies have already focused on the food-grade expression of CEase, but they are all aimed at the biosynthesis of epilactose. Herein, we reported for the first time the biosynthesis of lactulose using the recombinant food-grade Bacillus subtilis. Lactulose biosynthesis was optimized by varying lactulose-producing CEases and expression vectors. Caldicellulosiruptor saccharolyticus CEase and pP43NMK were determined to be the optimal CEase and expression vector. Fine-tuning of CEase expression was investigated by screening a beneficial N-terminal coding sequence. After fed-batch cultivation, the highest fermentation isomerization activity reached 11.6 U/mL. Lactulose was successfully produced by the broth of the engineered B. subtilis with a yield of 52.1 %.
乳糖向功能性乳糖衍生物的生物转化越来越受到关注。乳果糖是一种重要的高价值乳糖衍生物，已广泛应用于制药、营养保健品和食品工业。乳果糖可以通过纤维二糖2-表异构酶（CEase）由乳糖酶促生产。已有多项研究聚焦于CEase的食品级表达，但它们均旨在表乳糖的生物合成。在此，我们首次报道了使用重组食品级枯草芽孢杆菌生物合成乳果糖。通过改变产乳果糖的CEase和表达载体对乳果糖生物合成进行了优化。确定嗜热栖热放线菌CEase和pP43NMK为最佳CEase和表达载体。通过筛选有益的N端编码序列研究了CEase表达的微调。补料分批培养后，最高发酵异构化活性达到11.6 U/mL。工程化枯草芽孢杆菌的发酵液成功生产出乳果糖，产率为52.1%。
