Orr. ACT IV.. HFJihUUTY A^'D ENVIRONMEl^T 63 



fact, the results of these two authors do not agree. Kay- 

 ser studied the formation of the optical isomers of lactic 

 acid by different strains of microbes cultured on various 

 sugars. He used 14 bacterial species or strains, with 

 which he performed 61 experiments. His data, which are 

 sunmiarized in Table 10, show that there are strains which 

 always produce the laevorotatory lactic acid, others 

 which always produce the dextrorotatory isomer and 

 finally some which yield a racemic mixture. Kayser's 

 results (1894), therefore, coincide not with Pere's (1893) 

 but with the data of recent investigators, particularly 

 with the thorough observations of Katagiri and Kitahara 

 (1937). In only one of the 61 experiments of Kayser (the 

 last one marked w^ith an asterisk in the table) was dextro- 

 rotatory lactic acid produced on one sugar (glucose) and 

 laevorotatory lactic acid on another (maltose). Since 

 this single excej^tion might have resulted from an in- 

 sufficient purity of the bacterial culture employed (cf. 

 Pederson and his collaborators, 1926), one comes to the 



TABLE 10 



ixfluexce of various sugars i.\ the nutritive medium ox the optical 



Properties of the Lactic Acid Produced by Different Bacteria 



(Kayser, 1894) 

 (The letters a, b, c, . . . refer to the species and strauis of bacteria, 

 most of which were not completely identified; the letters 1, d. and dl 

 indicate the optical rotation of the lactic acid produced; the figures 

 (1) and (2) after Maltose and Lactose mean that two media of dif- 

 ferent composition were used with each one of these sugars.) 



