ZYMOGENIC BACTERIA 211 



Methane (CH 4 ) and Mucilaginous Fermentation. This 

 form of fermentation is due to the action of enzymes, which 

 are secreted by several species of bacteria, on cellulose. Spiril- 

 lum rugula is one of the bacteria which is concerned in the 

 production of methane (CH 4 ). It is not an infrequent occur- 

 rence for wine, beer, vegetables, and especially milk, to be- 

 come slimy and appear mucilaginous in character. This 

 condition is due to the bacterial enzymes fermenting carbo- 

 hydrate compounds. The mucilaginous, gumlike substance 

 (galactan) is very similar to cellulose. The fermented 

 materials absorb a great amount of water and thus form a 

 sticky mass. 



The bacterial enzymes invert the cellulose or lactose into 

 dextrose, and this in turn is broken up into methane, carbon 

 dioxide, hydrogen, and fatty acids. The reactions are uncer- 

 tain after the inversion, but it seems probable that the 

 methane results from the splitting of alcohols which are 

 formed in the process. The following represents the reaction : 



(C 6 H 10 O 5 ) n -h D H 2 O = 3nCO 2 + 3 n CH4 (methane). 



Methane is one of the principal constituents of petroleum 

 gas (40 per cent). Coal yields as high as 80 or 90 percentage 

 of methane. 



Fermentation of the Higher Alcohols, Aromatics, and 

 Fatty Acids. Glycerine and mannite (propenyl alcohol) 

 on fermentation by the enzymes of Bacillus ethaceticus and 

 others may form ethyl alcohol, acetic acid, formic acid, 



