Shen Xiuru, Liao Lingtong, Zhang Guoqiang, Zhou Jingwen, Li Jianghua, Du Guocheng
Science Center for Future Foods, Jiangnan University, Wuxi, 214122, China.
National Engineering Research Center for Cereal Fermentation and Food Biomanufacturing, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu, 214122, China.
Synth Syst Biotechnol. 2023 Jan 5;8(1):168-175. doi: 10.1016/j.synbio.2023.01.001. eCollection 2023 Mar.
Lactase is a member of the β-galactosidase family of enzymes that can hydrolyze lactose into galactose and glucose. However, extracellular lactase production was still restricted to the process of cell lysis. In this study, lactase-producing JNXR-2101 was obtained using a rapid and sensitive method based on the fluorescent substrate 4-methylumbelliferyl-β-d-galactopyranoside. The purified enzyme was identified as a neutral lactase with an optimum pH of 9. To facilitate extracellular production of lactase, a putative mannoprotein KLLA0_E01057g of was knocked out. It could effectively promote cell wall degradation and lactase production after lyticase treatment, which showed potential on other extracellular enzyme preparation. After optimizing the fermentation conditions, the lactase yield from mannoprotein-deficient JNXR-2101ΔE01057g reached 159.62 U/mL in a 5-L fed-batch bioreactor.
乳糖酶是β-半乳糖苷酶家族的一种酶，能够将乳糖水解为半乳糖和葡萄糖。然而，胞外乳糖酶的生产仍局限于细胞裂解过程。在本研究中，使用基于荧光底物4-甲基伞形酮基-β-D-吡喃半乳糖苷的快速灵敏方法获得了产乳糖酶的JNXR-2101。纯化后的酶被鉴定为一种最适pH为9的中性乳糖酶。为了促进乳糖酶的胞外生产，敲除了推定的甘露糖蛋白KLLA0_E01057g。溶菌酶处理后，它能有效促进细胞壁降解和乳糖酶生产，在其他胞外酶制备方面显示出潜力。优化发酵条件后，在5-L分批补料生物反应器中，缺乏甘露糖蛋白的JNXR-2101ΔE01057g的乳糖酶产量达到159.62 U/mL。
