32(> BACTERIOLOGICAL CHEMISTRY 



In this latter case the fatty acids and proteins in the 

 sewage also contribute their quota to the decomposition 

 products. 



The primary stages in the breakdown of cellulose are 

 probably hydrolytic with formation, by the action of 

 the enzyme cellulase, of the disaccharide cellobiose which 

 in turn is hydrolysed by the enzyme cellobiase to glucose. 

 These enzymes have been obtained in cell-free filtrates of 

 Cellulohacillus myxogenes and C. mucosus. Cellobiose 

 and glucose can usually only be detected as products of 

 the action of these organisms when the air supply is 

 restricted (preventing further degradation) or when the 

 growth of the organisms is prevented by such substances 

 as toluene. Dextrins may form an intermediate step 

 between cellulose and cellobiose. Some confirmation of 

 the intermediary nature of cellobiose and glucose is 

 afforded by the fact that the action of CytopJuiga 

 hutchinsoni on cellulose is inhibited by the presence of 

 0-1 per cent, of glucose or 1 per cent, of cellobiose which 

 are used preferentially. The acids and other products 

 of these micro-organisms in all probability arise by the 

 usual metabolic reactions from the glucose so formed. 

 It has been claimed that the gums so often produced by 

 cellulose decomposing organisms may consist of oxycellu- 

 lose and polyuronides formed by the oxidative break- 

 down of the cellulose, but the evidence is not at all 

 sound. 



It has been shown that the fatty acids are broken 

 down by spore -bearing thermophilic bacteria, with the 

 production of methane and carbon dioxide only in 

 yields as high as 90 per cent. The process is in effect 

 an oxidation-reduction process involving water, as shown 

 by the empirical equation : — 



n— 2 n 1-2 :}n— 2 ,^^ 

 CuHanOa + ^-H^O > — — CO^ + ^^^H^, 



(fatty acid) 



