ORGANIC ACIDS AND OTHER PRODUCTS 



15 



Studies have also been directed toward finding optimum condi- 

 tions for the formation of gluconic acid. Herrick and May (1928) 

 secured good yields in 10-day-old cultures, incubated at 25° to 

 30° C, in the following medium: 



Glucose 



Magnesium sulphate 

 Disodium phosphate 



200.00 grams 

 0.25 gram 

 0. 10 gram 



Potassium chloride 

 Sodium nitrate 

 Water 



0.05 gram 

 1 .00 gram 

 1000.00 ml 



Kardo-Ssysojewa (1933) recorded increased yields from de- 

 creasing total salts but increased yields if the nitrates were in- 

 creased in acid media. He grew mats of A. niger in nutrient-sugar 

 solution in the presence of calcium carbonate, and after pouring 

 off this solution replaced it with one of 20% sugar to which he 

 added calcium carbonate. After 4 days he secured 11.89 grams 

 of gluconic acid from 11.36 grams of sugar, and after 5 days 12.19 

 grams of gluconic acid from 11.76 grams of sugar. Traces of 

 citric acid were present also, but no oxalic acid. 



Fumaric acid. In 1911 Ehrlich demonstrated that Rhizopus 

 nigricans produces small amounts of fumaric acid from glucose 

 and fructose. These observations have subsequently been con- 

 firmed, and in 1918 Wehmer (1918) reported yields of 60 to 70% 

 from a species of Aspergillus that he named A. fiimaricus. This 

 organism gradually declined in fumaric acid-producing ability 

 after repeated subculture and formed instead gluconic, malic, and 

 citric acids. Galactose and arabinose have also been utilized in 

 fumaric acid fermentation. Other fungi that have been found 

 capable of producing this acid include Rhizopus oryzae, R. tritici, 

 and Yenicillium griseo-jidvum [Raistrick and Simonart (1933)]. 



Gottschalk (1926) and Butkewitsch and FedorofT (1929) se- 

 cured calculated yields of fumaric acid of approximately 50% 

 from R. nigricans. They found that this acid may arise in an 

 alcoholic fermentation as follows: 



CHoOH N 

 2C0 2 + 2 



CrHioO 



+02 



12^6 



CH 3 



Alcohol 



/COOH 



21 



-H 2 



CH 3 



Acetic acid 



CH 2 • COOH 

 CH 2 ■ COOH 



Succinic acid 



H 2 



CH • COOH 

 CH • COOH 



Fumaric acid 



