Racemiase, an enzyme which catalyses racemization of lactic acids.

SO-CAETID fermentation lactic acids are generally believed to be inactive, since it was ascertained by Phelps & Palmer [1917] and Pederson et al. [1926] that optically inactive lactic acid was produced in many natural fermentations. The lactic acid in Sake was found to be the inactive form, although not only inactive lactic acid-producing organisms (Lactobacillus sake), but also optically active lactic acid-formers (Leuconostoc mesenteroides var. sake) (1-former) and dor d+ dl-forming varieties of Lactobacillus sake were isolated by us [Katagiri et al. 1934], from yeast mashes for sake manufacture. Pederson et al. [1926] and again Tatum et al. [1932] observed that acetone-butyl alcohol-producing organisms (Clostridium acetobutylicum) affected optically active lactic acid-formers by causing them to form inactive lactic acid, and they suggested that this special property of'Cl. acetobutylicum would explain the reason why fermentation lactic acids are inactive. Such a phenomenon would be very peculiar as was pointed out by Stephenson [1930], since a stereochemical specificity is observed in nature in almost all biochemical reactions. In our previous papers [1935, 1936, 1, 2, 3] it was reported that various kinds of dl-lactic acid-formers had the remarkable property of racemizing the lactic acids owing to the presence of an enzyme termed "racemiase" [1936, 3]. Direct racemization of lactic acid was also verified by us [1936, 4] with Cl. acetobutylicum. It was therefore concluded that the special effect of the acetonebutyl alcohol-producing organism in rendering the fermentation lactic acid inactive, would also be due to the action of the bacterial racemiase. The enzymic racemization of lactic acid recently has been recorded by Tatum et al. [1936] with acetone bacteria. Thus the production of inactive lactic acid in natural fermentations would be due, in a great measure, to the racemiase of dl-lactic acid-formers. In the present paper the occurrence of racemiase is recorded in Staphylococcus ureae. Many authors have discussed the question whether the optical properties of fermentation lactic acids would be modified by the cultural conditions even when pure cultures of lactic acid bacteria were used. From this discussion it would appear that inactive lactic acid can be obtained when optically active lactic acid-formers are used under certain cultural conditions. In the present work, experiments were carried out with various strains of lactic acid bacteria, in order to ascertain whether any modification of the form of fermentation lactic acid would be produced by varying the conditions of cultivation.