Production and characterization of low-calorie turanose and digestion-resistant starch by an amylosucrase from Neisseria subflava.

This study was intended to produce turanose and resistant starch (RS) using recombinant amylosucrase from Neisseria subflava (NsAS). Turanose production yield maximally reached to 76% of sucrose substrate at 40 °C by NsAS treatment. To evaluate turanose as a low-calorie functional sweetener, its hydrolysis pattern was investigated in continuous artificial digestion system. When turanose was consecutively exposed through small intestinal phase, only 8% of disaccharide was hydrolyzed. Structural modification of gelatinized corn or rice starch was carried out by NsAS with sucrose as a glucosyl donor. Non-digestibility of enzyme-modified starches increased to 47.3% maximally through branch-chain elongation, enough for chain-chain association and recrystallization. Obviously, NsAS-modified starches had higher gelatinization peak temperatures than native counterparts, and their paste viscosity was inversely related to their digestibility due to elongated-chain induced retrogradation. These results suggested that NsAS could be a vital biocatalyst candidate in food industry to produce next generation low-calorie carbohydrate food materials.