3. Metabolic activity of lactic acid bacteria
Lactic acid bacteria are generally mesophilic but can grow at temperatures as low as 58C or as high as 458C. Similarly, while the majority of strains grow at pH 4.0–4.5, some are active at pH 9.6 and others at pH 3.2. Strains are generally weakly proteolytic and lipolytic and require preformed amino acids, purine and pyrimidine bases and B vitamins for growth (Stamer, 1976; Cogan and Hill, 1993; Jay, 1996). An overview of the lactic acid bacteria is presented in the texts edited by Wood and Holzapfel (1996) and Salminen and von Wright (1998) and the reader is directed to these sources for information relating to aspects such as taxonomy, biochemistry, physiology, ecology and applications.