The Proteolytic Action of Certain Lactic Acid Bacteria

Abstract

Although the action of the lactic acid bacteria on carbohydrates has been the subject of many investigations, comparatively little attention has been paid to their proteolytic activity. Kulp and Rettger (1924) found that from 2 to 6 per cent of the proteins i milk were broken down by L. acidophilus and L. bulgaricus.Oila-Jensen (1919) studied the proteolytic action of a large number of lactic acid bacteria on the proteins of milk and Witte's peptone broth. In milk from 0 to 22.7 per cent of the total nitrogen was changed into soluble forms and in Witte's peptone the amino nitrogen produced varied from 0.5 to 33.9 per cent of the total. Ammonia nitrogen generally amounted to less than 2 per cent of the total nitrogen. Itano (1916) in studying the influence of hydrogen ion concentration upon the proteolytic activity of S. lacticus obtained an increase of 8.7 to 33.5 per cent in the amount of amino nitrogen. Sears (1916) reported that B. acidi-lactici produced much more ammomna and amino nitrogen when glucose was left out of the medium than when it was included.Various criteria have been used by different investigators as indexes of proteolysis. The early investigators, Smith (1897) and Peckham (1897), took putrefactive products as a test, Heller (1921) employed pH changes, Hall (1922) used liquefaction of coagulated proteins and gelatin as standards, Kendall and Walker 1 This work was supported in part by a grant from the special research fund of the University of Wisconsin. The authors are indebted to Miss Katherine M. Bolliger for assistance in the analytical work.

Comparative Metabolism of the R and S Variants of Lactobacillus plantarum (Orla-Jensen)

“…Weaver (1932) noted that L. acidophilus and L. bulgaricus did not grow in sugar-free basic media. However, proteolytic activities of lactobacilli have been noted by Gorini (1922), Kendall and Haner (1924a, b), Kulp and Rettger (1924), Peterson, Pruess and Fred (1928), and Frazier and Rupp (1931).…”