Enzymatic synthesis of lactulose by commercial ß-galactosidase from Klyveromyces lactis

In this research hydrolysis and transgalactosylation reactions in lactulose synthesis from lactose and fructose by commercial s-galactosidase from Klyveromyces lactis were studied. At first stage, lactose and lactulose conversion to the hydrolysis products was investigated. Morethan 90% of lactose and 75% of lactulose were consumed with addition of 100 ml of enzyme solution (3000 U/ml) tothe 100 g of 5% (w/w) sugar solutions in 40°C and pH6.7 after 1 and 3 hr respectively. Then transgalactosylation reaction for synthesis of lactulose in the presence of lactose as galactosyl donor and fructose as an acceptor was studied and the effect of some parameters such as reaction time, acceptor concentration, temperature, enzyme amount on maximal produced lactulose concentration was investigated. Maximum lactulose concentration of 1.22% was achieved by adding of 400 ml of enzyme solution (3000 U/ml) to the 100 g of sugars solution, containing 10% (w/w) lactose and 30% (w/w) fructose, in 40°C and pH 6.7 after 120 minutes.