SPECIAL INDUSTRIAL FERMENTED PRODUCTS 651 



The plant has since been closed, as have others of a similar nature, 

 which operated during the war in acetone manufacture. 



LACTIC ACID* 



Lactic acid is used in large quantities in the tanning industry for 

 deliming and plumping the heavier hides. It also finds some appli- 

 cation in other industries as well. There is, therefore, a moderate 

 demand for the acid in commerce. 



Several raw materials have been used in its preparation. The 

 waste liquor from concrete beet silos carries about 2 per cent, of this 

 acid and has been used direct in tanning or the liquid treated to recover 

 the lactic acid itself. Amylaceous substances such as corn starch, 

 barley malt, etc., are the usual raw materials, although waste milk 

 from creameries or the whey from cheese factories may also be employed 

 to advantage. 



If starchy materials hydrolyzed with either acid or malt are used, it. 

 is possible to carry out lactic fermentation at 50 or higher and thus 

 effectively eliminate the butyric organisms, which constitute the 

 principal source of trouble. If milk or whey is the culture medium, 

 B. bidgaricus or other vigorous lactic organism adapted to milk may be 

 used. 



The fermentation is carried out in the presence of chalk (CaCO 3 ) 

 or zinc carbonate. Either calcium or zinc lactate is formed. The 

 zinc lactate crystallizes satisfactorily on concentration; calcium lactate 

 is more soluble. The salt is next decomposed with sulphuric acid and 

 distilled, preferably in vacuo, in apparatus not corroded by lactic acid 

 vapors. 



Among the various processes described in the literature, the Fried- 

 bergerf method appears to possess merit although it is difficult to see 

 in what way his process is novel to the extent of being patentable. 

 He uses a pure culture of B. delbruckii from a maltose nutrient medium 

 which is transferred to sterile dextrose nutrient medium containing 

 asparagin and peptone. When it has become accustomed to the 

 dextrose, the culture is grown in a sterilized medium and the starter so 

 produced used to ferment a sterilized liquid made by hydrolysis of any 

 starchy material with hydrochloric acid. The fermentation takes 



* Prepared by W. V. Cruess. 



t English Patent 2507, January 31, 1917. 



