The Preparation of Glycolytically Active Washed Cells of Lactobacilli.

Lactobacillus casei is a useful organism for microbiologists and biochemists because it can be used in certain microbiological asays. Extensive investigations have been conducted and considerable information has been obtained concerning the nutritional requirements of this homolactic organism by measuring its growth response to various substances. On the other hand, investigations with washed cells of this organism have been surprisingly few in spite of the fact that experimental conditions with such cell preparations can be more readily defined and controlled than in studies conducted with growing organisms in culture media. That the optimlum growth conditions and nutritive requirements for the pro-duction of cells of a particular organism vary with the enzyme system to be studied has been well established. Thus, Gale (1940) found that cells of Streptococcus faecalis harvested from a trypsin-digested casein medium with a terminal culture pH below 5.0 possessed an active tyrosine decarboxylase system. Wood and Gunsalus (1942) found that cells of Streptococcus mastitidi* grown in a tryptone, yeast extract, low glucose medium harvested before the culture pH had dropped below 6.8 displayed excellent glucose dehydrogenase properties. Bellamy and Gunsalus (1944) subsequently confirmed and extended Gale's findings, describing a medium, synthetic except for the incorporation of acid-hydrolyzed gelatin and a folic acid concentrate, which supported cells demonstrating good decarboxylation properties. Wood and his associates (1945) used LactobaciUus casei cells grown in a glucose, yeast extract medium to degrade glycogen hydrolyzates to lactic acid. Reithel (1946) prepared a cell-free extract of Streptococcus theinwphilus, which fermented lactose and glucose to lactic acid in the presence of adenosine triphosphate (ATP), from cells grown on a medium containing Difco broth, lactose, and peptonized milk. The present study is an attempt to devise a medium which could be used to prepare fairly large amounts of washed cells of lactobacilli (which could be lyophilized or used in the preparation of cell-free extracts) which would actively ferment glucose to lactic acid. No attempt was made to obtain an intimate knowledge of the chemical composition of such a medium.