MANNITOL-PRODUCING ORGANISMS IN SILAGE 435 



Evidence that organisms of the type of M39 are concerned in 

 the production of mannitol was furnished unexpectedly in two 

 instances as follows: 



1. A control stover silo, which had been opened after steri- 

 lization only for the purpose of adding sterile water, contained 

 considerable mannitol when it was examined after a period of 

 about two weeks. Microscopic examination showed many 

 organisms morphologically resembling M39 and corn juice 

 agar plates inoculated with the material yielded colonies like 

 those of M39; transfers were made to corn juice agar and when 

 the organisms were inoculated back into the usual test materials 

 mannitol was found in considerable quantities after a holding 

 period of from ten to twenty days. It seems that the presence 

 of the mannitol-producing organisms in the silo was due to 

 accidental inoculation since the organism is not exceptionally 

 heat resistant and accordingly would not be expected to survive 

 the heating during sterilization; moreover the other control 

 showed neither organisms nor mannitol. 



2. One of the yeasts isolated from silage was inoculated into 

 a sterile stover silo and after the usual holding period an exami- 

 nation showed the presence of mannitol. When the silage was 

 examined microscopically, in addition to the yeast, an organism 

 morphologically similar to M39 was found in large numbers; 

 this organism was isolated by plating on corn juice agar and 

 proved capable of producing mannitol when inoculated into the 

 usual test materials. Although a microscopic examination of 

 the original yeast culture had shown no bacteria, it is entirely 

 possible that a very small number of organisms of the M39 

 type may have been present in the culture and had thus been 

 inoculated into the silo along with the yeast. Contamination 

 of the silo, either at the time of inoculation or later when the 

 silo was opened to release pressure, is another means of explain- 

 ing the results secured. 



Influence of oil at the surface of the liquid on mannitol production 



Since the formation of mannitol is to be looked upon as a re- 

 ducing process, it was thought that the addition of sterilized 



