金黄色类节杆菌来源的菊糖果糖转移酶在大肠杆菌中的高效表达及发酵条件优化OA

Difructose anhydride Ⅲ(DFA Ⅲ)is a novel functional sweetener characterized by enhanced mineral absorption,low ca-loric value,and excellent acid-base stability.Its bioproduction is critically dependent on inulin fructotransferase(IFTase).As the key en-zyme for industrial-scale synthesis of DFA Ⅲ,the development of high-yield IFTase-producing engineered strains and their corresponding optimized fermentation processes is of great importance.In this study,the IFTase gene derived from Paenarthrobacter aurescens QL1.001 was cloned and heterologously expressed in Escherichia coli,achieving an extracellular IFTase activity of 714.32 U/mL.Single-factor opti-mization was performed to improve the medium composition and fermentation conditions of the recombinant strain.The optimal medium(g/L)was determined as follows,tryptone 10.0,yeast extract 20.0,glycerol 5.0,K2HPO4 9.0,and KH2PO4 0.93.The optimal fer-mentation conditions were pH 8.0,24 ℃,0.6 mmol/L IPTG,and an induction time of 48 h.Under these optimized conditions,the IF-Tase activity increased to 1 449.83 U/mL,representing a significant increase compared with the initial shake-flask yield and approximate-ly a 20-fold improvement over the wild-type strain.This activity level was the highest in the literature for recombinant IFTase expression.These results demonstrated that the constructed recombinant E.coli strain and optimized fermentation conditions enabled the highly effi-cient production of IFTase,providing valuable technical parameters and theoretical support for the large-scale production of DFA Ⅲ.