title: Batch and continuous synthesis of lactulose from whey lactose by immobilized β-galactosidase.
abstract: In this study, lactulose synthesis from whey lactose was investigated in batch and continuous systems using immobilized β-galactosidase. In the batch system, the optimal concentration of fructose for lactulose synthesis was 20%, and the effect of galactose, glucose and fructose on β-galactosidase activity was determined for hydrolysis of whey lactose and the transgalactosylation reaction for lactulose synthesis. Galactose and fructose were competitive inhibitors, and glucose acted as a noncompetitive inhibitor. The inhibitory effects of galactose and glucose were stronger in the transgalactosylation reaction than they were in the hydrolysis reaction. In addition, when immobilized β-galactosidase was reused for lactulose synthesis, its catalytic activity was retained to the extent of 52.9% after 10 reuses. Lactulose was synthesized continuously in a packed-bed reactor. We synthesized 19.1g/l lactulose during the continuous flow reaction at a flow rate of 0.5 ml/min.
authors.affiliation: Department of Chemical and Biological Engineering, Korea University, 5 Ga, Anam-dong, Sungbuk-gu, Seoul 136-701, Republic of Korea.
authors.forename: Yoon Seok
authors.initials: YS
authors.lastname: Song
authors.forename: Hee Uk
authors.initials: HU
authors.lastname: Lee
authors.forename: Chulhwan
authors.initials: C
authors.lastname: Park
authors.forename: Seung Wook
authors.initials: SW
authors.lastname: Kim
mesh_terms: D000818:Animals; D061249:Batch Cell Culture Techniques / Q000379:methods*; D002417:Cattle; D046508:Culture Techniques / Q000379:methods*; D004800:Enzymes, Immobilized / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D007716:Kluyveromyces / Q000201:enzymology; D007785:Lactose / Q000737:chemistry*; D007792:Lactulose / Q000138:chemical synthesis*; D008892:Milk / Q000737:chemistry*; D001616:beta-Galactosidase / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D007792:Lactulose; D001616:beta-Galactosidase; D007785:Lactose