An Ecological Study of Lactic Acid Bacteria: Isolation of New Strains of Lactococcus Including Lactococcus lactis subspecies cremoris

Abstract

We previously described a colony hybridization method for isolation of bacteria from natural environments using rRNA probes and the successful use of the method for the isolation of dairy lactococci. Herein we report the use of the method for further isolation of dairy lactococci. Thirty-eight samples from US vegetables and other plant species; 24 individual raw milk and milk product samples from the US, People's Republic of China, Morocco, Yugoslavia, and Ukraine; and 12 other samples from US dairy farms were examined for lactic acid bacteria by the colony hybridization method. Lactococcus lactis ssp. lactis occurred on potato, cucumber, sweet pea, bean, cantaloupe, corn, body and tail of cows, colostrum, raw milk from goats and cows, cottage cheese, and cream. Lactococcus lactis ssp. lactis biovar diacetylactis was isolated from raw cow milk from Morocco and from raw goat milk and cottage cheese from Yugoslavia. Lactococcus lactis ssp. cremoris was isolated from raw milks from Morocco. People's Republic of China, and Ukraine and from cottage cheese and raw milk from Yugoslavia. Acid-producing properties of isolated strains were variable. Many strains were fast acid producers, most were acceptable for flavor when grown in milk, and a few produced a malty flavor, which is considered to be a defect.