Enzymatic lactose hydrolysis by beta-galactosidase (lactase) was investigated with respect to the formation of oligosaccharides. An analysis of the formation of oligosaccharides and their control is important in the development of technical applications for enzymatic lactose hydrolysis. The available literature data on transfer reactions of lactase were reviewed, compared, and presented in a concise tabular form. Mechanisms and possible ways of modelling enzymatic lactose hydrolysis, including formation of oligosaccharides, are presented.

Enzymatic lactose hydrolysis using two yeast and two fungal lactases that are of current technical interest was studied. The enzymes were compared regarding their oligosaccharide production. Parameters influencing oligosaccharide formation, together with the effect of immobilization were examined and conditions minimizing oligosaccharide content in the hydrolysis product were proposed. Enzymatic whey hydrolysis was also considered. A possibility of enzymatic lactose recombination from its hydrolysis products was shown.

Enzyme adsorption from a finite bath (batch adsorption) onto porous spherical supports is investigated both experimentally and theoretically using beta-galactosidase and Duolite ion-exchange resin as a model system. Efficient numerical techniques are presented that have been used in conjunction with a parameter estimation routine to evaluate adsorption isotherm constants. Results show that even for adsorption processes lasting almost 10 h, the majority of the enzyme is confined to the outer half of the support and, for high initial enzyme concentrations in the bath, this loading takes place as a slowly moving front. Information on the enzyme distribution has practical importance in the design of immobilized enzyme reactors that in previous works have almost always been analyzed assuming a uniform catalyst distribution.

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The problem of whey disposal or its meaningful utilization has plagued the dairy industry for many decades. In some countries, like Switzerland and Norway, where the art of cheese making in small plants still prevails, whey is disposed of locally by pig feeding or by manufacture of whey cheese.Worldwide, however, with modern dairy plants sometimes producing over 1 million liters of whey daily, traditional means of whey disposal are no longer acceptable. The same can be said about UF permeate from the manufacture of cheese or whey protein by ultrafiltration, which is becoming increasingly popular. Because whey and UF permeate, having BOD values of about 50,000 mg 02/1, represent a significant environmental problem, they cannot be discharged without expensive treatment. Therefore, methods of whey or UF-permeate upgrading are being intensively studied. The enzymatic hydrolysis of lactose to glucose/galactose by P-galactosidase with simultaneous protein recovery is one of the most promising methods' currently being investigated.Basic research in our laboratory on P-galactosidase and its imm~bilization~~' reached a stage where a scale-up of the enzyme reactor was required. A bigger reactor needed large quantities of substrate and the use of pure lactose was no longer economical. Hence, sweet whey, which was provided by the Swiss dairy industry, was chosen as a substrate. This called for other unit operations for whey processing before enzymatic hydrolysis as well as for final product tailoring. Therefore a complete pilot plant had to be constructed. It also gave us an opportunity to test the stability of our catalyst in the environment of a whey processing plant. An economic analysis of enzymatic whey hydrolysis, based on the pilot plant results, was attempted.The plant was built around 3-1, fixed-bed reactors with the enzyme catalyst developed earlier.2*3 A capacity of 800-1000 I of whey per day was chosen as a feasible plant size. A production cycle of 20 or 40 hr and a 4-hr sanitation cycle was used. Total automation was required as in an industrial plant. "Quickfit" glass was chosen for a construction material allowing easy plant construction and visual inspection under operating conditions. The products, a glucose/galactose syrup and a whey protein concentrate, had to be of a quality enabling them to be offered to the food industry for application and market tests. A glucose analyzer, was used for the analysis of glucose; H PLC for lactose, glucose, galactose, and oligosaccharides. A simplified flow diagram of the "Lactohyd" is given in FIGURE 1.The enzyme catalyst, developed and optimized earlier,2.3 was at first based on P-galactosidase from Aspergillus niger. This was expensive and its use required a new sclcctive lactose crystallization step.4 Four fixed-bed reactors were installed so that evcry combination of their connections was possible. Three of them were used for hydrolysis with the fourth one kept on stand-by, waiting to be exchanged with any