| abstract |
The invention belongs to the technical field of enzyme engineering, and particularly relates to lactase for generating galactooligosaccharide as well as preparation and an application of the lactase. According to the invention, lactase (BglD305 derived from Bacillus circulans B2301 and BglD derived from Bacillus circulans ATCC 31382) molecules from two sources are taken as the basis for molecular evolution, so as to obtain new lactase enzyme molecules with high galactooligosaccharide synthesis efficiency and good expression performance; the high-producing strain lactase is further constructed, the lactase can be efficiently synthesized during the submerged fermentation, and the enzyme molecule is secreted into the culture medium, the high-activity enzyme preparation is directly prepared from the fermentation supernatant, and the lactase expression level can achieve 2208 U/mL; the fermentation manufacturing cost of lactase is reduced, the fermentation manufacturing process is simplified, and the quality of the lactase preparation is improved. |