Hydrolysis of lactose

D (+) Galactose is a constituent of numerous polysaccharides It is best obtained by acid hydrolysis of lactose (milk sugar) a disaccharide of d glucose and d galactose L (—) Galactose also occurs naturally and can be prepared by hydrolysis of flaxseed gum and agar The principal source of d (+) mannose is hydrolysis of the polysaccharide of the ivory nut a large nut like seed obtained from a South American palm... 

Lactase (P-galactosidase) is produced commercially from the lactose fermenting Klujveromjcesfragilis. The enzyme has a pH optimum of 6—7 and is used ia the hydrolysis of lactose ia milk or skim milk. 

D-Galactose Hydrolysis of lactose. Can be changed to glucose in the liver and metabolized. Synthesized in the mammary gland to make the lactose of milk. A constituent of glycolipids and glycoproteins. Failure to metabolize leads to galactosemia and cataract. 

ESI-MS has been used for the quantification of a number of substrates and products of enzymatic reactions [56,57]. Hsieh et al. report the use of ion spray mass spectrometry (a technical variation of electrospray ionization) coupled to HPLC for the kinetic analysis of enzymatic reactions in real time [58]. The hydrolysis of dinucleotides with bovine pancreatic ribonuclease A and the hydrolysis of lactose with 3-galactosidase were monitored and the resulting data were used for the estimation of and v x of these reactions. Another field of application of electrospray mass spectrometry is the screening of combinatorial libraries for potent inhibitors [31,59]. 

Lipomyces kononenkoae + P-galactosidase Hydrolysis of lactose-containing wastewater 4-90 5 n.d. n.d. [50]... 

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). 

The hydrolysis of lactose conveys a number of desirable properties to whey—increased sweetness for one. Lactase-treated whey can be used as a sweetener in various foods such as ice cream, bakery products, beverages and corrfectionery. This treatment can save large qrrantities of whey from going to waste and presenting a potential pollution hazard. 

Bakken, A.P., Hill, C.G. and Amnndson, C.H. (1992) Hydrolysis of Lactose in Skim Milk by Immobilized Beta Galactosidase Bacillus-Circulans. Biotechnology and Bioengineering, 39, 408-417. 

Gekas, V. and Lopez-Leiva, M. (1985) Hydrolysis of Lactose A Literature Review. 

Any factor that accelerates the crystallization of lactose shortens the storage life of the product. At very low temperatures (below — 23°C), neither lactose crystallization nor casein flocculation occurs, even after long periods. Enzymatic hydrolysis of lactose by /S-galactosidase before freezing retards or prevents lactose crystallization and casein precipitation in proportion to the extent of the hydrolysis (Figure 2.14). 

Figure 2.17 Production of oligosaccharides during the hydrolysis of lactose by /5-galactosidase . lactose , monosaccharides O, glucose , oligosaccharides , galactose (modified from Mahoney, 1997).

Acid Hydrolysis. Lactose is resistant to acid hydrolysis compared to other disaccharides such as sucrose. In fact, organic acids, such as citric acid, that easily hydrolyze sucrose are unable to hydrolyze lactose under the same conditions. This is useful in analyzing a mixture of these two sugars, because the quantity of sucrose can be measured by the extent of these changes in the optical rotation of reducing power as a result of mild acid hydrolysis. The speed of hydrolysis of lactose varies with time, temperature, and concentration of the reactant, as shown in Table 6.8. 

Enzymatic Hydrolysis. The literature on the hydrolysis of lactose with /3-galactosidase (lactase) enzymes is enormous available reviews discuss specific aspects of their use (Zadow 1984 Harju and Kreula 1980 Shukla 1975). There has been significant progress in this field, and several processes are or almost commercially feasible. 

Asp, N. G., Burval, A., Dahlquist, A., Hallgren, P. and Lundblad, A. 1980. Oligosaccharide formation during hydrolysis of lactose with Saccaromyces lactis lactase (Maxi-lact R). II. Oligosaccharide structures. Food Chem. 5, 147-153. 

Coughlin, J. R. and Nickerson, T. A. 1975. Acid-catalyzed hydrolysis of lactose in whey and aqueous solutions. J. Dairy Sci. 58, 169-174. 

Mulherin, B., Muller, T., Delaney, R. A. M. and Harper, W. J. 1979. Acid catalyzed hydrolysis of lactose with cation exchange resins. N.Z. J. Dairy Sci. Technol. 14, 127. 

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. 

Toba, T. and Adachi, S. 1978. Hydrolysis of lactose by microbial /3-galactosidases. Formation of oligosaccharides with special reference to 2-o-/3-i>galactopyranosyl-D-glu-cose. J. Dairy Sci. 61, 33-38. 

Methylation and hydrolysis of lactose gives a tetra-O-methyl-D-galactose and 2,3,6-tri-O-methyl-D-glucose. The same galactose derivative can be obtained from the methylation and hydrolysis of D-galactopyranose. 

The hydrolysis of lactose (D-galactosyl-jS-(l,4) D-glucose) to D-galactose and D-glucose occurs with AG° of —4.0 kcal/mole. 

Glucose obtained by mammals from the diet through intestinal hydrolysis of lactose, sucrose, glycogen, or starch is brought into the hexose phosphate pool through the action... 

The food industry is a fertile area for biocatalysis applications high-fructose corn syrup (HFCS) from glucose with glucose isomerase, the thermolysin-catalyzed synthesis of the artificial sweetener Aspartame , hydrolysis of lactose for lactose-intolerant consumers, and the synthesis of the nutraceutical i-camitine in a two-enzyme system from "ybutyrobetaine all serve as examples. 

One of the largest-scale processes with enzymes is the hydrolysis of lactose to glucose and galactose (250 000 tpy) (Liese, 1999). As a significant fraction of consumers, especially in Asia, are lactose-intolerant, a condition which gives rise to rashes and stomach ailments, hydrolysis of lactose has considerable utility for the manufacture of lactose-free milk (Silk ). 

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