Screening of food-grade microorganisms for biotransformation of D-tagatose and cloning and expression of L-arabinose isomerase
生物转化生产D-塔格糖的食品级菌种选育及L-阿拉伯糖异构酶的克隆表达

L-Arabinose isomerase (L-AI) is an intracellular enzyme that catalyzes the reversible isomerization of D-galactose and D-tagatose. Given the widespread use of D-tagatose in the food industry, food-grade microorganisms and the derivation of L-AI for the production of D-tagatose is gaining increased attention. In the current study, food-grade strains from different foods that can convert D-galactose to D-tagatose were screened. According to physiological, biochemical, and 16S rDNA gene analyses, the selected strain was found to share 99% identity with Pediococcus pentosaceus, and was named as Pediococcus pentosaceus PC-5. The araA gene encoding L-AI from Pediococcus pentosaceus PC-5 was cloned and overexpressed in E .coli BL21. The yield of D-tagatose using D-galactose as the substrate catalyzed by the crude enzyme in the presence of Mn2+ was found to be 33% at 40 °C.