ORGANIC ACIDS AND OTHER PRODUCTS 77 



oxygen tension an intermediate substance is formed which be- 

 comes converted into lactic acid, alcohol, and carbon dioxide, 

 with little loss of potential energy. 



Ethyl alcohol. Sac char omyces cerevisiae has long been known 

 for its ability to metabolize ethyl alcohol. As long ago as 1873, 

 however, Fitz (1873) noted that Mucor racemosus is also capable 

 of transforming sucrose into alcohol. Of the closely related genus 

 Rhizopus, ethvl alcohol is known to be formed bv R. nigricans, 

 R. tritici, R. arrhizus, and R. oryzae. 



Fusarium lini, the cause of flax wilt, gives yields of the same 

 order of magnitude as those from cultivated yeasts [Letcher and 

 Willaman (1926), White and Willaman (1928)]. It will ferment 

 almost any hexose and in addition almost any pentose, the pentoses 

 not being utilized in this manner bv baker's yeast. Many other 

 species of Fusarium, moreover, are able to decompose glucose 

 with the production of alcohol, each differing in relative yields; 

 as might be anticipated, a variety of other products appear dur- 

 ing the fermentation [Raistrick et al. (1931)]. 



Species of Aspergillus and Penicillium have been tested for their 

 ability to produce alcohol. As a result it is known that 96 species 

 or strains of Aspergillus and 75 of Penicillium possess this capa- 

 bility. Among them are A. niger and several members of the 

 A. glaiicus group and the A. flawis-oryzae-tamarii group. Yuill 

 (1928) is among those who have studied alcoholic fermentation 

 by A. flavits. Other notable alcohol-forming molds are Eidamia 

 catemriata, E. viridescens, Trichoderma lignorum, and Helmintho- 

 sporhnn gemadatiim. 



Ethyl acetate. This fruity ester was demonstrated by Rai- 

 strick et al. (1931) to be formed by Fenicillium digitatum, a com- 

 mon mold associated with the decay of citrus fruits, when grown 

 on glucose solution. They state that it is not known to be formed 

 by any other mold. Presumably ethyl acetate originates by a 

 Cannizzaro reaction from acetaldehyde, an anaerobically formed 

 respiratory product. 



Glycerol. Connstein and Liidecke (1919) considered the 

 principles involved in the commercial production of glycerol by 

 fermentation. It is a matter of common knowledge that this 

 compound is formed during fermentation by yeasts, and as has 

 been shown in Chapter 3, high yields can be secured by the addi- 



