The use of mesophilic cultures in the dairy industry

Abstract

The use of mesophilic starter cultures, containing group N Streptococcus and Leuconostoc species, in the dairy industry is examined. Bacteriophage attack is identified as the main cause of culture inhibition and criteria used to select stable mixed-strain starter cultures and phage-insensitive defined strains are established. The key aspects of culture propagation and storage are highlighted, as well as bulk-culture protection based on physical exclusion of phage and the use of phage-inhibitory media. Developments in the application of starter culture systems in different countries are examined and show that significant process control and elimination of phage problems can be achieved.

Physiological and genetic regulation of rRNA synthesis in Lactococcus

“…111 dairy products they are used primarily to convert lactose to lactic acid but in addition they contribute to the flavours characteristic of those products (Daly, 1983). With the development of molecular biology techniques a significant effort is being made, in several research laboratories, to understand the physiology and genetics of these industrially important bacteria.…”

Plasmid Transfer via Transduction from Streptococcus thermophilus to Lactococcus lactis

“…Bacteriophages of Streptococcus thermophilus and Lactococcus lactis, two important starter strains in the dairy industry (5,25), share significant sequence homology (3,6). Therefore, horizontal gene transfer between the two genera has to be supposed.…”

Cloning and partial sequencing of the proteinase gene complex from Lactococcus lactis subsp. lactis UC317

“…Members of the genus Lactococcus are used as starter bacteria in the manufacture of a range of fermented milk products and consequently are of considerable commercial importance (Daly, 1983 ;Sandine, 1988). Lactococci are nutritionally fastidious and have complex amino acid requirements (Thomas & Pritchard, 1987).…”