DECOMPOSITION OF NON-NITROGENOUS ORGANIC MATTER 461 



decomposed by various aerobic and anaerobic bacteria and fungi. 

 Sugars are claimed to be the primary products formed from the hy- 

 drolysis of pectins. Among the secondary products, we find volatile acids 

 (acetic and butyric), hydrogen and carbon dioxide. Some organisms 

 produce formic, lactic and succinic acids, in addition to C0 2 , H 2 and 

 acetic acid. In the process of retting of flax and hemp, especially 

 under anaerobic conditions, alcohols and acetone are also formed, in 

 addition to the above products. 



Different species of fungi, like Rhizopus, both parasitic and non- 

 parasitic forms, secrete an enzyme pectinase which dissolves the middle 

 lamella of potatoes and of other plants. 106 



A similar enzyme is formed by Bac. carotovorus in the rotting of 

 carrots. 107 Microorganisms capable of decomposing pectins do not 

 usually possess the ability of attacking celluloses, otherwise the retting 

 process would be accompanied by the destruction of the celluloses 

 of the fibers. Certain levulosans are not readily acted upon by 

 microorganisms. 108 



Starches and their decomposition by microorganisms. Starches are 

 predominantly reserve materials, forming 60 to 70 per cent of the dry 

 weight of cereal grain. They are complex carbohydrates of the for- 

 mula (C6H l0 O 6 ) n -H 2 O but are more readily soluble than celluloses and 

 give the characteristic blue color with iodine. They swell in hot 

 water. They are much more readily acted upon by microorganisms 

 than the celluloses, due to the fact that a large number of soil forms, 

 including the bacteria, actinomyces and fungi, produce very active 

 diastatic enzymes which hydrolyze the starches first into dextrins of 

 different complexity, then into sugars (maltose and glucose). 



2(C 6 H 10 O 6 ) n + nH 2 = nC«H M Ou 

 starch maltose 



C12H22O11 -f- H2O = 2CeHi20s 

 maltose glucose 



The ability of certain bacteria and fungi to produce enzymes hydro- 

 lyzing starch is so great that the processes have been utilized for various 

 commercial purposes where diastatic enzymes are required. Certain 

 bacteria, however, are capable of breaking down starches with the 



106 Harter, L. L., and Weimer, J. L. A comparison of the pectinase produced 

 by different species of Rhizopus. Jour. Agr. Res., 22: 371-377. 1921; Amer. 

 Jour. Bot., 10: 127-132, 167-169. 1S95. 



107 Jones, 1909 (p. 203). 



108 Colin, H„ and Estienne, V. Utilisation de 16vulosanes par les organis- 

 mes. Bull. Soc. China. Biol., 6: 431^35. 1924. 



