16 BIOCHEMISTRY OF FUNGI 



Malic acid. Although malic acid has for years been considered 

 to be among the products formed by molds, proof was first pro- 

 vided by Wehmer (1928) in 1928. He secured small yields from 

 sucrose fermentation by Aspergillus fumaricus. Raistrick et al. 

 (1931) have found that several other fungi, among them species 

 of Aspergillus and Clasterosporium, can utilize glucose to form 

 malic acid. 



Succinic acid. It has long been known that yeasts produce 

 succinic acid during alcoholic fermentation. Moreover Fitz 

 (1873) recorded its presence in solutions during alcoholic fermen- 

 tation induced by Mu cor mucedo. Raistrick et al. (1931) showed 

 that a species of Clasterosporium isolated from cotton pulp, as 

 well as Fumago vagans, formed succinic acid from glucose. It 

 has also been shown to be produced by Aspergillus t err em 

 [Raistrick and Smith (1935)] and Penicillium aurantio-virens 

 [Birkinshaw and Raistrick (1932)]. This ability is doubtless pos- 

 sessed by a variety of fungi. 



Succinic acid, as has been shown, forms during fermentations 

 that give rise to such other acids as citric, gluconic, and fumaric, 

 with which it is chemically related; in consequence its origin may 

 be accounted for by the oxidative breakdown of sugars. On the 

 other hand, it may well arise from yeast proteins themselves or 

 from mold proteins. Accord seems not to have been reached on 

 the matter of the origin of succinic acid. 



Lactic acid. Until recently it was the general belief that only 

 bacteria, especially such species as Streptococcus lactis, Lactoba- 

 cillus acidophilus, and L. bulgaricus, are capable of causing lactic 

 acid to be formed. More recently however, several workers have 

 demonstrated this acid in sugar fermentations by species of Rhizo- 

 pus and Alucor, including Rbizopus oryzae, R. chinensis, R. ele- 

 gans, and R. tritici. A 40% yield from R. japonicus was reported 

 when this species was grown on 10% sugar solution containing 

 calcium carbonate. Waksman and Foster (1938) found a member 

 of the R. arrhizus group to be a very efficient lactic acid former 

 when grown in solutions containing glucose or starch. In the 

 presence of calcium carbonate 70 to 75% of the carbohydrate 

 was transformed into lactic acid. This yield is all the more re- 

 markable in that the fungus is supposedly strictly aerobic. Waks- 

 man and Foster, however, permitted it to form a film over the sur- 

 face of the liquid substrate, and within such a film under reduced 



