Development and Evaluation of Whole‐Cell Yeast Lactase for Use in Dairy Processing

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Abstract
A low‐cost industrial grade lactase was developed for one‐time use in dairy products. The preparation contained the entire biomass of a selected hyperproducing strain of the yeast Kluyveromyces fragilis. Intracellular lactase was made freely accessible to its substrate by permeabilization of the cell membrane with food compatible reagents. In 0.1M phosphate plus 0.4% methyl paraben, permeabilization was complete in 0.5–1 hr at 50°C, with 90% activity recovery from 180 g/L of cells. Whole‐cell lactase contained no viable cells and was free of proteolytic activity. Its pH optimum of 5.6–6.0 proved suitable for lactose hydrolysis concurrent with cottage cheese fermentation. Hydrolyzed whey was used in ice cream and bakers' yeast production.