304 BACTERIOLOGICAL CHEMISTRY 



If this were so it would be expected that the rechiction 

 product would be sorbitol, CH2OH.HCOH.HOCH.HCOH. 

 HCOH.CH2OH, corresponding in configuration to glucose, 

 and not mannitol, which corresponds to mannose. 

 Sorbitol, however, has never been detected in these 

 fermentations . It is possible that the conversion does not 

 involve glucose as such but the phosphorylated sugar, 

 shown to be fructose diphosphate in the case of yeast 

 fermentations. It has been shown that yields of 15 to 

 35 per cent, of mannitol, calculated on the sugar fer- 

 mented, are formed by the action of a white species of 

 Aspergillus on mannose, galactose, arabinose and xylose, 

 but not from fructose. No acid is formed. 



According to the Cannizzaro reaction theory of 

 mannitol and gluconic acid production, .the nature of the 

 product which accumulates depends on the optimum ^^H 

 conditions for the organism. Thus the white Aspergilli 

 thrive in a neutral medium of about pYL 6 to 7 and utilise 

 the gluconic acid, leaving mannitol in solution. A. niger 

 on the other hand, favours an aoid medium and utilises 

 the neutral product mannitol and allows gluconic acid to 

 accumulate. 



The moulds afford a better commercial source of 

 mannitol than bacteria, since they ferment the cheap sugar 

 glucose and not the expensive fructose, and do not require 

 organic nitrogen, in the form of peptone or yeast extract, 

 as do the bacteria. In addition the moulds produce 

 mannitol in almost pure solution with very few by- 

 products. Mannitol is used in the form of its hexa- 

 nitrate as a detonator. 



Products containing Sulphur, Arsenic or Selenium. — 



The cases of arsenical poisoning which used to occur as 

 a result of the action of fungi on wallpapers printed with 

 arsenic containing substances have long been considered 

 as due to the formation of volatile substances of the 

 type trimethyl arsine, (CH3)3As, which has been shown 



