重组地衣芽孢杆菌全细胞转化法制备D-阿洛酮糖OA北大核心CSTPCD

D-allulose(D-psicose)is a low-calorie functional sugar,which has many functions such as sucrose substitute,participat-ing in Maillard reaction,improving food gel process,etc.One of the methods of preparing D-allulose,biosynthesis,has many advantages such as simple purification steps,high product concentration,good environmental compatibility,etc.Therefore,the preparation of D-allu-lose by biosynthesis has become a research hotspot.In this study,Bacillus licheniformis is used to heterologously express D-psicose 3-epi-merase(DPEase)from Ruminiclostridium cellulolyticum H10 for the first time,which opens up a new expression vector pathway for D-al-lulose biosynthesis.Firstly,different promoters were selected to mediate the expression of DPEase,and the recombinant strain BL1 with the best expression effect was selected to optimize the whole-cell transformation and fermentation conditions.The optimized recombinant bacterial whole-cell transformation conditions were that the temperature was 65 ℃,the cell OD600 of the reaction system was 2,the reac-tion time was 10 minutes,and the substrate D-fructose was 100 g/L,which was utilized to explore the fermentation medium conditions,which was that the carbon source was 75 g/L sucrose,the initial pH was 7.5,and the temperature was 37 ℃.Finally,the whole-cell bio-synthesis transformation method was used,which was that the temperature was 65 ℃,D-fructose was 500 g/L,the cell OD600 was 30,and the reaction time was 20 minutes,the conversion rate was achieved at 30.3％,the D-allulose was converted to 120 g/L,and unit enzyme activity reached 33.3 U/mL.The conversion rate was increased to 69.8％by adding boric acid with a molar mass ratio of 0.4 to fructose in four stages of the reaction system.This study provides a certain reference value for the industrial production of D-allulose.