Fructosyltransferases are a class of glycoside hydrolases that catalyze fructosyl transfer reactions. Their core function is to transfer the fructosyl group from substrates such as sucrose to acceptor molecules. The catalytic mechanism relies on the synergistic effect of acid-base catalysis and covalent catalysis, achieving efficient transfer by forming a fructosyl-enzyme intermediate. These enzymes are characterized by strong substrate specificity and mild reaction conditions.
The core mission of fructosyltransferases is "transferring fructosyl groups". Using sucrose, a common ingredient in our daily diet, as the raw material, they hydrolyze glycosidic bonds to release energy, then precisely link free fructose molecules to acceptor molecules, thereby synthesizing functional sugars such as fructans and fructooligosaccharides. The process works as follows: sucrose molecules are split into glucose and fructose; the fructose moieties are then assembled into new sugar chains following specific rules, while glucose is released as a by-product. This catalytic reaction is highly specific, with the main products including 1-kestose and nystose-key components of prebiotics that have gained widespread popularity in the health food industry.
In the food industry, fructooligosaccharides synthesized under the catalysis of fructosyltransferases have a sweetness level of only 30%–60% that of sucrose. Yet they can selectively promote the growth of beneficial intestinal bacteria such as Bifidobacterium, improve the balance of the gut microbiota, and do not cause significant fluctuations in blood glucose levels. As a result, they are widely used in dairy products, beverages, baked goods and other food categories. For instance, yogurt fortified with fructooligosaccharides not only boasts a smoother texture but also exhibits enhanced probiotic activity.
Beyond the food sector, the application scenarios of fructosyltransferases are continuously expanding. In the industrial field, they can convert sucrose present in agricultural wastes like sugarcane bagasse and corn stover into oligosaccharides, providing raw materials for biofuel production. In the textile industry, they can break down pectin on the surface of bast fibers, making fabrics softer and more amenable to dyeing. In the chemical industry, they can catalyze the reaction between sucrose and alcohols or organic acids, synthesizing novel surfactants and fragrances.
With the advancement of biotechnology, the performance of fructosyltransferases is being constantly optimized. Research teams have conducted structural modifications on fructosyltransferases derived from Aspergillus niger, increasing the fructooligosaccharide conversion rate from 0.17% to 29.20%. Additionally, researchers have achieved high-efficiency expression of this enzyme using engineered Pichia pastoris strains, with the specific activity of the purified enzyme reaching 71.4 U/mg. These technological breakthroughs have reduced the cost of industrial-scale production and enabled the application of fructosyltransferases in an even broader range of fields.