earticle

영어

Lactulose (4-o-β-D-galactopyranosyl-D-fructose) is a non digestible disaccharide that is used medicinally as a treatment for portal systemic encephalopathy, chronic constipation, and hyperammonemia. In the food industry, the bifidus factor lactulose can be used as an ingredient that has greater sweetness and solubility than lactose. The biological synthesis of lactulose has been studied with β-galactosidases using lactose and fructose as substrate and co-substrate, which exhibits a low conversion yield. In this study, the enzymatic production of lactulose was attempted without the addition of fructose using a thermostable recombinant cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus as a new type of lactulose-producing enzyme. The conditions for maximum lactulose production from lactose, as a single substrate, by cellobiose-2-epimerase from C. saccharolyticus were determined to be pH 7.5, 80 C, 700 g/L lactose, and 150 U/mL of enzyme. Under the conditions, the enzyme produced the two bifidus factors lactulose at 408 g/L and epilactose at 107 g/L after 2 h. The yields of lactulose and epilactose from lactose and the productivities of lactulose and epilactose were 58%, 15%, 204 g/L/h, and 54 g/L/h, respectively. This is the first trial of enzymatic synthesis of lactulose using the single substrate lactose. These results will contribute to the industrial production of lactulose from lactose via an enzymatic process.