Beta‐galactosidase technology: A solution to the lactose problem

Abstract

Lactose, a disaccharide more commonly known as milk sugar, is and has been a major problem for the dairy and food industry. First, the majority of human adults are incapable of digesting it owing to the deficiency of the hydrolytic enzyme beta‐galactosidase and thus it is a health and nutritional problem; second, it is the main reason for the sandy texture of frozen food items and crystallization related problems in the manufacture of condensed milk; and third it is a major contributor to the overall “biological‐oxygen‐demand” load of dairy waste. Lactase or, more correctly, beta‐galactosidase, is the enzyme that specifically hydrolyzes lactose into glucose and galactose. This enzyme, when immobilized (fixed by physical and chemical forces) on solid supports can be used on a semi‐continuous or continuous basis in bioreactors for (a) large‐scale reduction of lactose content of milk and other dairy products, and (b) production of sweetener concentrates and food syrups. The latter process may employ another immobilized enzyme (glucose isomerase) that isomerizes glucose to fructose, a ten times sweeter sugar than lactose. This review offers a critical evaluation of the technologies of (a) large‐scale enzyme production, (b) enzyme purification, (c) enzyme immobilization, (d) immobilized enzyme kinetics, and (e) process kinetics of enzyme reactors and reactor performance. This newly emerging technology, no doubt, is a good and timely answer to the lactose related nutritional, technological, pollution and “food‐waste” problems. However, it raises a new question of galactose problem ‐ the well‐known disease cataract. The industry does not seem to be conscious of this fact. This author strongly believes that fermented milk products are the solution to both the problems, lactose and galactose, as they contain lower amounts of lactose and very little galactose because it is metabolized via cyclolitic and tricarboxylic acid cycle reaction sequences by the enzyme systems of resident microflora. However, enzymatic hydrolysis of lactose through commercial reactors promises to raise significantly the quality of some dietetic foods and medicinal preparations. There is no doubt that a total of 410 million pounds of lactose of which more than 85% is wasted annually within the United States alone can be converted into food grade syrups and sweeteners by the use of combined technologies of beta‐galactosidase and glucose isomerase. The overall economy and large‐scale industrial feasibility of this operation has yet to be determined. The activity by the industry in this general area seems to follow an almost exponential rate.