Physiological Characteristics of Lactic Acid Bacteria Near the Maximum Growth Temperature: I. Growth and Acid Production.

Little information is available on the growth and activity of bacteria at temperatures above the optimum, despite the fact that in many commercial processes the organisms used are often subject to temperatures higher than those most favorable for growth. In the manufacture of Swiss cheese, for example, starter cultures must not only survive the high temperatures used during cooking of the curd, but also must grow at temperatures close to their maximum for several hours. Preliminary investigations have indicated that rates of enzyme production and destruction and of enzyme activity were affected differently by growth at optimum temperatures and at those near the maximum for the organism. It was believed that investigations of the physiological activities of bacteria at near their maximum growth temperatures would add significant information to that regarding these activities at optimum temperatures. Barber (1908), using single cell isolations, studied the rates of multiplication of Escherichia coli at different temperatures. From the minimum temperature of about 10'C., the rate of multiplication increased rapidly as the temperature was raised to 37.50C.,