Hydrolysis lactose

The kinetic model of lactose hydrolysis was described by Scott et al (Biotechnol Bioeng Symp 15 431-445, 1985) as... 

Roy, 1. and Gupta, M.N., Lactose hydrolysis by Lactozym immobilized on cellulose beads in batch and fluidized bed modes., Proc. Biochem., 39 (2003) 325-332. 

Another established application in the dairy industry is the hydrolysis of lactose in milk and whey by lactases. Diminished digestibility problems, increased sweetness and prevention of lactose-crystal formation are the results. The lactose hydrolysis is worked out as a case later in this chapter (section 3.6). 

By pre-treating milk with lactase, all adults can enjoy milk and a whole range of other lactose-free dairy products can be made such as ice cream and yogurt. In the production of ice cream, lactose hydrolysis can also be used to improve certain properties such as the texture, sweetness and tendency to crystallize. The increased sweetness is also advantageous in the manufacture of flavored milk products because less sugar needs to be added. 

The following favorable aspects have determined the commercial success of lactose hydrolysis using lactases, despite of a number of disadvantages ... 

Figure 2.14 Effect of lactose hydrolysis (0, O 5, 10, 15, 20, A 30, A 50-85, x, %) on the stability of milk to freezing (modified from Tumerman, Fram and Comely, 1954).

Smart, J.B. (1993) Transferase reactions of /3-galactosidases - New product opportunities, in Lactose Hydrolysis, Bulletin 239, International Dairy Federation, Brussels, pp. 16-22. 

Many of the developments in lactose hydrolysis are described in reviews (Whey Workshop II 1979 Harju and Kreula 1980 Shukla 1975 Zadow 1984). 

A batch processing operation is the simplest method of achieving enzymatic lactose hydrolysis but suffers from the disadvantage that a large amount of recoverable enzyme is needed. For small users or manufacture on an irregular basis, the single-use enzyme procedure is probably the method of choice. 

Lactose hydrolysis with immobilized systems is the method of choice when regular production of hydrolyzed syrups on a large scale is required. The best-known of these is the Corning immobilized system, which uses lactase from Aspergillus niger covalently bound to a controlled-pore silica carrier. The particle size is 0.4 to 0.8 mm, the wet bulk density is 0.6, the activity is near 500 U/g at 50°C, and the optimal pH of operation is between 3.2 and 4.3. Estimated laboratory life is 2 years (Dohan et al. 1980). There are at least two of these plants in commercial operation, one in the Untied States and one in the United Kingdom, each a joint venture with Corning. 

The rate of hydrolysis is dependent on the mineral, lactose, and galactose concentrations, as well as on the temperature and pH. Many kinetic studies are available on lactose hydrolysis systems and enzymes (MacBean 1979). Inhibition of hydrolysis can be caused by galactose or sodium and calcium ions, so demineralization is often necessary. 

Dohan, L. A., Baret, J.-L., Pain, S. and Delalande, P. 1980. Lactose hydrolysis by immobilized lactase Semi-industrial experience. Enzyme Eng. 5, 279-293. 

Roberts, H. R. and McFarren, E. F. 1953. The chromatographic observation of oligosaccharides formed during lactose hydrolysis of lactose. J. Dairy Sci. 36, 620-632. 

The kinetic model of lactose hydrolysis by Aspergillus niger lactase can be described as follows (Scott et al., 1985) ... 

Yang, S. T. and M. R. Okos, "A New Graphical Method for Determining Parameters in Michaelis-Menten Type Kinetics for Enzymatic Lactose Hydrolysis "Biotechnol. Bioeng. 34 (1989) 763 - 773. 

The presence of galactose inhibits lactose hydrolysis by lactase. Glucose does not have this effect. 

N. Papayannakos, G. Markas, and D. Kekos, Studies on modelling and simulation of lactose hydrolysis by free and immobilized p g l tosidase from Aspergillus niger, Chem. Eng. J. 52-.B1 (1993). 

Jurado E, Camacho E, Luzon G, and Vicaria JM. Kinetic model for lactose hydrolysis in a recirculation hollow-fibre bioreactor. Chem Eng Sci, 2004 59(2) 397 05. 

D-galactosidase is enclosed in an osmotic barrier. This explanation applies, for example, to the greater dependence on pH value of lactose hydrolysis by disrupted Kluyveromyces (Saccharomyces) fragilis than by intact cells.583 Accordingly, a system of stereospecific transport across the plasmalemma is now recognized to be the initial requirement for the utilization of /3-D-galactosides by intact cells of Kluyveromyces fragilis.223,584... 

Lactose hydrolysis in milk (milk products for lactose intolerant people) Lactase... 

---