Whey protein concentrate as a nutrient supplement for lactic acid bacteria

Addition of 1 or 2% of a whey protein concentrate (WPC) to a whey-based medium used for fermentation with Lactobacillus delbrueckii subsp. bulgaricus 11842 or Streptococcus thermophilus ST20 has produced significantly higher bacterial counts and much faster acidity development than the control whey or whey UF permeate media. Industrial whey fractions of alpha-lactalbumin or beta-lactoglobulin used as nutrient supplements in the same concentrations as the WPC resulted in smaller but still noticeable effects. Addition of Bacto-peptone, an enzymatic protein digest, had no effect on the growth of L. delbrueckii subsp. bulgaricus 11842. The observed growth stimulation was not due to the increased lactose content of the broth resulting from the addition of the whey protein preparations. The beneficial effect has not been compromised by sterilization of the media at 121 degrees C/15 min which resulted in a high degree of protein denaturation and flocculation. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.