CHARACTERIZATION OF LACTASE IMMOBILIZED ON COLLAGEN: CONVERSION OF WHEY LACTOSE BY SOLUBLE AND IMMOBILIZED LACTASE

The use of immobilized enzymes in the food industry: a review

The production of high fructose corn syrups was greatly facilitated by the use of immobilized glucose isomerase. Similarly, in Japan, the fermentation industry proved its processing efficiency for amino acids through the use of immobilized amino acid acylase. This article discusses the use of soluble enzymes in the food industry followed by a section on the various available methods to immobilize enzymes. Once enzymes are immobilized, many of their operational parameters could be altered. Rationale for the determination of the effects of immobilization is provided. A relatively new concept is the use of a single matrix for immobilizing more than one enzyme. Immobilized multi-enzyme systems offer many attractive advantages; however, such a process also raises some interesting questions about kinetics. These questions and their suggested answers are discussed in the penultimate section. The major emphasis of this article is on the use of immobilized enzymes in the food industry. Two systems--amino acylase and glucose isomerase--have been demonstrated to be techno-economically feasible. Immobilization of other enzymes, such as glucoamylase, lactase, protease, and flavor modifying enzymes, has received some attention. The potential of these new systems are also discussed.

Chemical modificiation of collagen and the effects on enzyme-binding: mechanistic considerations

The effect of structural modification on the enzyme-binding capacity of collagen has been studied using beta-galactosidase (E. coli K12) immobilized to collagen membrane by the impregnation procedure. The apparent steady-state activities of the resultant collagen-enzyme complexes were determined as a means of evaluating the enzyme-binding capacity of the modified collagen. In addition, the amount of enzymic protein bound to the collagen support was determined by the tryptophan content of the complex. The tertiary structure of the collage matrix was modified by cross-linking with the difunctional reagent, glutaraldehyde, and by aging in the dry state. Such structural modifications were found to markedly reduce the enzyme (beta-galactosidase) binding capacity of collagen films. The enzyme-binding capacity of the crosslinked collagen membrane was completely restored by proteolytic enzyme treatment of the aged film but only partly so for the glutaraldehyde treated films. Proteolytic enzymes used to treat a dispersion of collagen microfibrils prior to casting into a membrane also resulted in an increase in enzyme-binding. The effect of structural modification of collagen on enzyme-binding and the locus of enzyme attachment are discussed.

Milk and its role in the American diet

A decline in milk consumption is postulated as a possible factor contributing to poor nutritional status. Certain common prejudices against milk may, rightly or wrongly, act as barriers to its consumption and, therefore, to its nutritional contributions. Beliefs such as "adults don't need milk;" "raw milk is better than pasteurized milk;" "nonwhite people shouldn't drink milk;" "saturated fat and cholesterol 'cause' heart disease;" "cows are ecologically unsound;" and "nutrition doesn't sell milk" can be counteracted in light of current scientific knowledge and information. It is reaffirmed that milk, in moderation, is a desirable inclusion in most people's diets.