166 AGEICULTUEAL AND INDUSTRIAL BACTERIOLOGY 



sponding fatty acids and glycerine. For example, certain 

 microorganisms live in butter and produce lipases which 

 may decompose stearin in accordance with the following 

 reaction : 



(C„H3sC02)3C3H5 + SHjO + lipase 

 Stearin 



= SCiiHasCOOH + CjHs (OH), + lipase 

 Stearic acid Glycerine 



Lipases have been described for certain species of molds but 

 they are not very common among the bacteria. They may 

 be demonstrated by preparing an emulsion of a suitable fat, 

 such as butter fat, or one of the vegetable oils, in agar. 

 Microorganisms grown upon the surface of such a medium 

 will show ability to hydrolyze the fat by the clearing of the 

 medium immediately surrounding the colony. 



The Splitting and Oxidizing Enzymes. — The most im- 

 portant of the so-called splitting enzymes are the zymase 

 of yeast, and the lactacidase of the lactic acid bacteria. The 

 enzyme zymase in the presence of phosphoric acid is capable 

 of transforming the monosaccharide sugars such as dextrose, 

 into alcohol and carbon dioxide. There probably are one or 

 more intermediate steps in the process, but the transforma- 

 tion may be illustrated by the equation : 



C,H,,0, = 2C,H,0H + 2C0, 

 Dextrose Alcohol 



This enzyme is characteristic of most species of yeasts ; it is 

 present also in a few of the molds and probably in some 

 species of bacteria. The enzyme is intracellular. Lactaci- 

 dase likewise transforms sugars, including the monosac- 

 charides, with the end product lactic acid. Here again there 

 are probably several intermediate steps in the process, but 

 the ultimate transformation may be indicated by the equa- 

 tion: 



C,Hi,0, = 2CH3CHOHCOOH 

 Dextrose Lactic acid 



