Physiological Characteristics of Lactic Acid Bacteria Near the Maximum Growth Temperature

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Abstract
Lactobacillus bulgaricus growing at 49.5[degree]C, just below its maximum temp., produced as much lactic acid in a carrot-liver medium after multiplication had ceased as has been produced during growth; at 37[degree]C there was a close relationship between rates of acid production and of growth; at 49.5[degree] an increase in size of inoculum increased the rate of growth and the size of the maximum population obtained, but at 37[degree]C, only the length of the lag phase was affected. When 4-. 7-, 12-, and 16-hr. cultures, respectively, were used as inocula, the lag phase became longer as the age of the inoculum was increased; the amt. of acid produced in 24 hrs. was the same; but less growth was obtained with the older inocula. At 49.5[degree] most growth and most acid were obtained with a 7-hr. inoculum. L. bulgaricus produced a little more volatile acid in milk at 49.5[degree] than at 37[degree], but Streptococcus thermophilus showed little difference at the 2 temps. There was no difference in the distribution of the 2 isomers of lactic acid at the 2 temps. with either of the lactic cultures.

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