DECOMPOSITION OF NON-NITROGENOUS ORGANIC MATTER 439 



The following equations were suggested 35 to explain the anaerobic 

 decomposition of celluloses: 



C 6 H 10 O 6 + H 2 -> 2 CH 3 • CO • COOH + 2 H 2 



Pyruvic acid 

 CH 3 • CO • COOH + H 2 -> CH 3 • CHOH • COOH 



Lactic acid 



CH 3 • CO • COOH -> CH 3 • CHO + C0 2 

 acetaldehyde 



2 CH 3 • CHO + H 2 -> CH 3 • CH 2 • OH + CH 3 • COOH 



2 CH 3 -CHrOH -> CH 3 COOH + 2 CH 4 



Lactic acid may also break down to give butyric acid 



2 CH 3 • CHOH • COOH -* CH 3 • CH 2 • CH 2 • COOH + 2 C0 2 + 2 H 2 



Decomposition of cellulose by aerobic bacteria. Cellulose decomposi- 

 tion by aerobic bacteria can be studied by suspending filter paper in a 

 shallow layer of a medium containing an appropriate nitrogen source 

 and the necessary minerals and inoculated with a pure or crude culture 

 of bacteria, or with soil or manure. At room temperature, the cellu- 

 lose will be found to be rapidly decomposed with the formation of a 

 slime or mucilage which may be colored yellow or red. Carbon dioxide 

 is formed abundantly but no other gas, so that no visible "fermenta- 

 tion" is found to take place; small quantities of acids are formed in 

 the medium. The cellulose is largely macerated and the fibers 

 separated from one another and gradually reduced to a pulp. Some 

 organisms are very active and others are very slow. With some species 

 isolated by Kellerman and associates, 36 the principal by-products were 

 found to consist of formic and acetic acids, while others gave rise only 

 to traces of fatty acids; no aldehydes, ketones or alcohols were formed. 

 The aerobic bacterium Spirochaeta cytophaga uses cellulose as the only 

 source of carbon and produces a pigment related to the carotin group, 

 also some mucilage, which does not give rise to optically active com- 

 pounds on hydrolysis, and small quantities of fatty acids, chiefly 

 butyric. The mucilage is extracted in the crude "humus" fraction in 

 soil analysis. 37 



Decomposition of cellulose by thermophilic bacteria. Thermophilic 

 bacteria destroy cellulose very actively. A nutrient solution contain- 



36 Langwell and Lymn, 1923 (p. 202). 

 » 6 Kellerman et al., 1914-1916 (p. 197). 

 17 Hutchinson and Clayton, 1919 (p. 195). 



