1 78 OPTICALLY ACTIVE FERMENTATION PRODUCTS 



strychnine, it can be decomposed into its two optical components, viz., dextro- 

 rotatory sarcolactic acid and levo-rotatory lactic acid. 



However, the most important method of separation is that in which the 

 activity of micro-organisms is called into play. This method, also, was proposed 

 by Pasteur in 1860. He sowed certain lower fungi the precise species cannot 

 now be ascertained in a solution of optically inactive ammonium racemate, and 

 found that the levo-rotatory properties of the liquid gradually increased ; and 

 that after a certain lapse of time ammonium levo-tartrate alone was detect- 

 able. It must therefore be concluded that certain ferments are endowed 

 with selective powers. In the present instance, the organism has separated 

 the racemic acid into its two optically active components, one of which (the 

 D-tartaric acid) it consumes, whilst the other (the L-acid) is liberated. Since 

 Pasteur's time this separating power has been utilised in various ways, two 

 examples of which are now given. In the first place, J. LEWKOWITSCH (I.) in 

 1882 dissociated the optically inactive mandelic acid, C 6 H 5 CH.OH COOH, 

 into its two active components in this manner. On the other hand, P. 

 FRANKLAND and W. FREW (III.) allowed their Bacillus ethaceticus to react on the 

 calcium salt of the optically inactive glyceric acid, CH,OH CH.OH COOH, 

 whereby its dextro-rotatory component was obtained, the levo- component being 

 consumed. 



140. The Production of the Stereoisomerie Lactic Acids 



by fermentation merits closer attention. In the first place, it should be men- 

 tioned that only the three isomers of ethylidene lactic acid, CH 3 CH.OH COOH, 

 are in question, since ethylene lactic acid, CH 2 .OH CH 2 COOH, has hitherto 

 been obtained by purely chemical means alone. The sub-title, fermentation 

 lactic acid, so long borne solely by the inactive form of ethylidene lactic acid, 

 is now recognised as also appertaining to both its stereoisomers, so that the term 

 is now synonymous with ethylidene lactic acid generally. Of the two active 

 forms, the so-called paralactic acid was the first to be prepared by the fer- 

 mentation method, the discovery being due to M. VON NEXCKI and N. SIEBER (I.) 

 in 1889. These observers found that certain tumours in an animal affected 

 with symptomatic anthrax contained (in addition to the characteristic bacillus 

 of this disease) an anaerobic fission fungus, which produces large quantities of 

 paralactic acid (i.e. dextro-lactic acid) in saccharine media, and is on that account 

 named Micrococcus acidi paralactici. On the other hand, the aforesaid patho- 

 genic bacillus, under the same conditions, produces inactive lactic acid. 



Levo-lactic acid was first prepared in the year 1890 by FR. SCHARDINGER 

 (II.), by means of the fermentative activity of a short-rod species found in a 

 Hungarian well-water, and to which the name of Bacillus acidi Icevolactici has 

 been given. In size this organism greatly resembles Hueppe's Bacillus acidi 

 lactici. It ferments dextrose, saccharose, lactose, and glycerin, the resulting 

 products being levo-lactic acid, a little ethyl alcohol, a quantity of carbon 

 dioxide, and an unspecified combustible gas. The zinc salt of inactive lactic acid 

 is obtained by crystallisation from a warmed solution of the zinc salts of this 

 levo-lactic acid and of paralactic acid. 



So far as is known at present, the Schizomycetes species forming levo-lactic 

 acid are of less frequent occurrence in nature than those producing either 

 inactive or dextro-lactic acid. K. GIJNTHER and H. THIERFELBER (I.) examined 

 a large number of samples of sour milk, in none of which could they find levo- 

 lactic acid. Neither did they succeed in isolating from the milk any fission 

 fungus capable of forming this acid, but always obtained either inactive or 

 dextro-lactic acid, or a mixture of both. This, however, does not imply that 



