CHAPTER XVI 



THE FERMENTATION PRODUCTS OF J 

 THE LOWER FUNGI I 



SINCE Wehmer's classical work on the production of m 

 oxalic acid by fungi in 1891 a vast bulk of data on | 

 mould fermentations has accumulated, as a result of 

 which it emerges that there are three main differences 

 between bacterial and mould fermentations. The first 

 of these is that the moulds appear to have considerably 

 greater and more diverse synthetic powers than the 

 bacteria. They are able to produce a large variety of 

 compounds, aromatic as well as aliphatic, besides the 

 normal cell constituents, proteins and nucleic acids. The 

 range of these synthetic powers is indicated by the 

 following examples of some of the types of product 

 encountered : Benzopyrone, quinones, phenolic acids, 

 heterocyclic compounds, pyrones, long chain fatty acids, 

 fats, polysaccharides and sterols. Secondly, and 



perhaps most important from a practical point of view, 

 the fungi produce non-volatile, often polybasic, acids, 

 of which oxalic, citric and gluconic acids are the most 

 important. They usually produce about 0-1 per cent., 

 and never yield more than 1 per cent., of volatile acids. 

 Lactic acid has only been reported as a mould product 

 from Monilia, Mucor rouxii, Rhizopus oryzce and Rhizopus 

 chinensis. If volatile acids are formed during the meta- 

 bolism of the fungi they are immediately further broken 

 down ; indeed, it has been shown that the volatile 

 acids are even more readily attacked by fungi than are 

 sugars. Bacteria, on the other hand, produce large 

 quantities of such volatile acids as acetic, propionic, 

 butyric and lactic acids. Thirdly, the moulds never 

 seem to give rise to hydrogen or metliane among their 



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