Engineered strain for producing tagatose and construction method and application thereof

Abstract

The invention discloses an engineered strain for producing tagatose and a construction method and application thereof. According to the construction method, by regulating intracellular glucose metabolism, the enzymatic activity of 6-phosphofructokinase in cells is reduced, the enzymatic activity of glucokinase and the enzymatic activity of glucose 6-phosphate isomerase are improved, therefore, thecontent of fructose-6-phosphate in the cells is increased, a tagatose synthesis path composed of tagatose-6-phosphate 3-epimeriase and tagatose-6-phosphate phosphorylase is constructed, and a fructose metabolism path composed of fructose permease and fructokinase is constructed. The glutamic acid corynebacterium recombination strain is obtained and can synthesize tagatose by metabolizing glucose,fructose or saccharose. Compared with currently reported fructose biotransformation tagatose synthesis methods, the construction method of the engineered strain has the advantages of being easy to operate and facilitating separation and is suitable for large-scale tagatose production.

Description

technical field [0001] The invention belongs to the field of biotechnology, and in particular relates to an engineering bacterium for producing tagatose, a preparation method of the engineering bacterium and its application in fermenting and producing tagatose. Background technique [0002] Tagatose (D-Tag) is a rare monosaccharide that occurs naturally. It is the ketose form of galactose and the epimer of fructose. The sweetness properties are similar to sucrose, and the calories produced are only one-third of sucrose, so it is called a low-calorie sweetener. Tagatose has excellent nutritional properties such as low calorie value, zero glycemic index, blood sugar passivation, caries-free, prebiotic effect and antioxidant activity. Tagatose has four major functions: low energy, lowering blood sugar, improving intestinal Intestinal flora and anti-caries. The U.S. Food and Drug Administration (FDA) listed D-tagatose as a safe food (GRAS) additive in 2003. The safety of taga...

AI Technical Summary

Problems solved by technology

[0003] At present, the production of tagatose is mainly through chemical synthesis and biotransformation. Chemical synthesis requires multiple protection and deprotection steps, resulting in high energy consumption, low yield, and high production costs.

The biotransformation method uses galactose as a raw material, and L-arabinose isomerase catalyzes the synthesis of D-tagatose. This method has a high catalytic synthesis efficiency, but galactose is expensive, and the conversion rate of this reaction is only 50%. The high cost of product separation and the high production cost of tagatose make this biotransformation method unable to be widely used

Relevant patents propose to establish an in vitro catalytic system to convert fructose into tagatose, and increase the conversion rate through phosphorylation and dephosphorylation steps, but expensive ATP is required as a coenzyme, which will increase the production cost of tagatose and is not suitable for large-scale production. Therefore, it is urgent to develop a new method for the synthesis of tagatose with low cost, low pollution and high yield.

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