652 MICROBIOLOGY OF SPECIAL INDUSTRIES 



place in the presence of sterile chalk. Near the end of fermentation the 

 temperature may be lowered and cultures of B. bulgaricus may be 

 added. It is claimed that liquids fermented in this way are of sweet 

 odor and free from butyric acid. The liquid is treated with 0.3 to 0.5 

 per cent, tannin, calculated on the weight of carbohydrates originally 

 present. The tannin unites with the albumins of the liquid resulting 

 in clarification. The clarified liquid is filtered and decomposed with 

 sulphuric acid in the usual way. 



Wehmer* reports that 15 grams of glucose will yield under average 

 commercial conditions about 10.5 grams of lactic acid; whereas the 

 theoretical yield is 15 grams according to the following equation: 



C 6 H 12 6 = 2 C 2 H 4 OHCO 2 H. 

 The reactions involved in the purification of the acid are: 



2 C 2 H 4 OHC0 2 H + CaCO 3 = Ca(C 2 H 4 OHCO 2 ) 2 + CO 2 + H 2 O. 



Ca(C 2 H,OHCO 2 ) 2 + H 2 SO 4 = CaSO 4 + 2 C 2 H 4 OHCO 2 H. 

 The CaSO 4 separates as a precipitate. 



Wehmer has held lactic bacteria for six years in calcium lactate 

 formed during fermentation and suggests this method as a commercial 

 means of storing starters of desirable strains of the organism. 



Hexamethylene tetraminf has been used instead of calcium carbon- 

 ate to neutralize the lactic acid slowly during fermentation and the 

 sugar remaining is fermented with yeast for alcohol production. 



Milk and whey should be sterilized before use and fermented with 

 pure cultures of lactic organisms to minimize the constant danger from 

 butyric acid fermentation which is favored by neutralization of the 

 liquid with calcium carbonate. 



CITRIC ACIDJ: 



Most of the citric acid of the world's commerce is obtained from 

 lemons, although it is possible to convert various sugars into citric acid 

 by fermentation processes. 



In California citric acid is made from cull lemons from the packing 

 houses. Lemons are graded very closely during packing in order that 

 the quality of the packed fruit shall be uniform and the fruit attractive 

 in appearance. This results in a large percentage of culls which until 



* Jour. Soc. Chem. Ind., 1906, page 112. 



t A. Pollak, U. S. Patent 1123920, January, 1915. 



t Prepared by W. V, Cruess. 



