Properties of Porcine and Yogurt Lactobacilli in Relation to Lactose Intolerance

¹ Department of Microbiology, University of Otago, PO Box 56, Dunedin, New Zealand

Lactobacilli that had been isolated from the stomach of piglets were tested for properties relevant to the production of fermented milk products for consumption by lactose-intolerant humans. The strains were characterized for ß-galactosidase activity, the ability to reduce the lactose concentration of milk, viability, and pH of the fermented milk over a 30-d period. Strains that had favorable attributes were studied further, and the optimal pH for ß-galactosidase activity, ability to grow in the presence of bile salts, and ability to deconjugate bile salts were determined. Commercial yogurts were also examined to determine whether products varied in characteristics that might affect tolerance of milk products by lactose-intolerant subjects. The Lactobacillus sp. isolated from pigs had lower ß-galactosidase activity than did Lactobacillus delbrueckii ssp. bulgaricus strains ATCC 11842 and NCDO 1489 and strains of lactobacilli isolated from yogurt. The ß-galactosidase activity of all strains decreased rapidly once the fermented milk was stored at 4°C. Strain JB10, originating in the stomach contents of the piglets, had properties that were useful for the manufacture of fermented milk products for lactose-intolerant humans. Milk fermented by this strain had a lactose concentration of about 4.0% and contained 6.6 x 10⁶ cfu/ml after storage at 4°C for 20 d. Strain JB10 produced a ß-galactosidase that was active at pH 5.5 (35% of the activity at pH 7.0) and was not inhibited by the presence of bile acids in the culture medium. ß-Galactosidase activity and lactose concentration varied among yogurts.

Key Words: lactose intolerance • yogurt • ßbeta;-galactosidase • lactobacilli

Submitted on November 12, 1996
Accepted on March 24, 1997