tailieunhanh - A new kinetic model proposed for enzymatic hydrolysis of lactose by a -galactosidase from Kluyveromyces fragilis

We study the enzymatic hydrolysis of lactose by a commercial enzyme from a selected strain of Kluyveromyces fragilis. The variables analyzed were: temperature (25–40 ◦C), enzyme concentration (– g l−1), lactose concentration (– M), and initial galactose concentration ( M). On the basis of the data analyzed, both published and in the present work, we propose a Michaelis–Menten kinetic model with inhibition by the product (galactose), which reveals that the substrate (lactose) and the product (galactose) present similar affinity for the active site of the enzyme. | Enzyme and Microbial Technology 31 (2002) 300–309 A new kinetic model proposed for enzymatic hydrolysis of lactose by a ␤-galactosidase from Kluyveromyces fragilis E. Jurado∗ , F. Camacho, G. Luzón, . Vicaria Departmento Ingenier´ıa Qu´ımica, Facultad Ciencias, Universidad de Granada, Granada 18 071, Spain Received 3 January 2002; accepted 21 March 2002 Abstract We study the enzymatic hydrolysis of lactose by a commercial enzyme from a selected strain of Kluyveromyces fragilis. The variables analyzed were: temperature (25–40 ◦ C), enzyme concentration (– g l−1 ), lactose concentration (– M), and initial galactose concentration ( M). On the basis of the data analyzed, both published and in the present work, we propose a Michaelis–Menten kinetic model with inhibition by the product (galactose), which reveals that the substrate (lactose) and the product (galactose) present similar affinity for the active site of the enzyme. © 2002 Elsevier Science Inc. All rights reserved. Keywords: Lactose hydrolysis; Kluyveromyces fragilis; Kinetic model; ␤-Galactosidase 1. Introduction Enzymatic hydrolysis of lactose is one of the most important biotechnological processes in the food industry because of the potentially beneficial effects on the assimilation of foods containing lactose, as well as the possible technological and environmental advantages of industrial application, including: 1. Elimination of lactose intolerance (3–70% depending on the populational group [1]), encouraging the utilization of lactose as an energy source, as well as calcium and magnesium assimilation from milk. 2. Formation of galacto-oligosaccharides during lactose hydrolysis to favor the growth of intestinal bacterial microflora. The presence of these compounds is considered desirable in foods [2,3]. 3. Improvement in the technological and sensorial characteristics of foods containing hydrolyzed lactose from milk or whey [4–7] such as: increased solubility (avoidance of .