Lactose enzymatic hydrolysis

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). 

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. 

Sucrose and lactose occur widely as the free sugars, lactose in the milk of mammals, and sucrose in fruit and plants (especially in sugar cane and sugar beet). Maltose is the product of enzymatic hydrolysis of starch, and cellobiose is a product of hydrolysis of cellulose. 

Membrane bioreactor Asymmetric poly-sulfone membrane Diffusion of carbohydrates in liquid-filled pores Enzymatic hydrolysis of lactose Whole cells of Sutfolobus solfataricus entrapped in the tube wall 65... 

The separation,purification and concentration of a thermosensitive bioactive compound from a lysate has been carried out combining UF, ion exchange and RO with significant cost reduction and productivity increase. Enzyme membrane reactors have been used for triglyceride enzymatic hydrolysis and product separation. Thermophi1ic,thermostable enzyme ultrafiltration membrane have been prepared, and used in high temperature lactose hydrolysis. 

Enzymatic hydrolysis of polysaccharides (cellulose, starch) or oligosaccharides (maltose, saccharose, lactose) for the synthesis of food products is another class of processes MBR have been applied to. Paolucci-Jeanjean et al [4.56] have recently reported, for example, the production of low molecular weight hydrolysates from the reaction of cassava starch over a-amylase. In this case the UF membrane separates the enzyme and substrate from the reaction products for recycle. Good productivity without noticeable enzyme losses was obtained. Houng et al [4.57] had similar good success with maltose hydrolysis using the same type of MBR,... 

Product Inhibition. In most microbiological and biochemical systems accumulation of end products exercises an inhibitory effect on the rate of the forward reaction. Stimulation by end product is thermodynamically improbable. One of the major products of hydrolysis of cellulose is cellobiose. There is a stimulation by cellobiose of Cx activity of Streptomyces spp. filtrates only when the substrate is solubilized by the introduction of various substituents—e.g., CMC, hydroxycellulose, cellulose acetate, etc. Stimulation is absent when unsubstituted cellulose is used (14). On the other hand, product inhibition is common. Cellobiose inhibits the hydrolysis of cellulose by filtrates of most of the 36 organisms tested. This action of cellobiose is believed to be that of an end product inhibiting an enzymatic hydrolysis in much the same manner that maltose inhibits hydrolysis of starch by a-amylase. The inhibitory effect of products varies with the organism from which the cellulase is derived. Thus, lactose is a very good inhibitor of the enzyme from... 

Sucrose is extracted from sugar cane and sugar beets and is purified and sold in very large amounts for use in foods. Maltose (malt sugar) is made by the enzymatic hydrolysis of starch, which is a polyglucose. Lactose is the sugar in milk. It is not as sweet as sucrose. 

Lactose (j8-D-galactopyranosyl-l-4-D-glucopyranose) is the major sugar of milk (Fig. 19). It is of interest that the ability to utilize either sucrose or lactose as a source of calories is dependent on their enzymatic hydrolysis to the constituent monosaccharides in the intestine. About one-third of the oriental population lacks the requisite galac-tosidase and is thus lactose intolerant this same problem occurs in some infants (developmentaUy related) and results in a colicky baby. 

In the synthesis of A-acetyllactosamin from lactose and A-acetylglucosamine with (3-galactosidase (289,290), the addition of 25 vol% of the water-miscible ionic liquid [MMIM][MeS04] to an aqueous system was found to effectively suppress the side reaction of secondary hydrolysis of the desired product. As a result, the product yield was increased from 30 to 60%. Product separation was improved, and the reuse of the enzymatic catalyst became possible. A kinetics investigation showed that the enzyme activity was not influenced by the presence of the ionic liquids. The enzyme was stable under the conditions employed, allowing its repeated use after filtration with a commercially available ultrafiltration membrane. 

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]. 

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. 

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. 

Lactose, phenylosotriazole, III, 38 a-Lactose, acetochloro-, I, 40, 41 Lactyl chloride, acetyl-, III, 367 Laminarin, IV, 275, 282 Langenbeck s formulation of enzymatic glycoside hydrolysis, V, 58 Larch, e-galactan of, II, 249 Larch manna. See Manna. 

In spite of all these difficulties, microdialysis has been successftilly coupled to several analytical techniques for the bioprocess monitoring. HPLC is commonly used and such systems have been apphed in the analysis of oligosaccharides [44,180], ethanol [181], enzymatic digestion of lactose in milk [182], studies on drug dissolution [183], saccharides in wastewater [184], starch hydrolysis products [185]. 

It is not always immediately apparent from an enzymatic reaction whether it should be treated with single- or dual-substrate enzyme kinetic expressions. Lactose hydrolase, which catalyzes the hydrolysis of lactose according to... 

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