INDUSTRIAL FERMENTATIONS 3l'5 



most of tlie remainder being found in the gimi ^\ hich the 

 organism produces. Organisms of the genus Cellulomonas 

 (small motile or non -motile rods which may be pigmented) 

 also attack cellulose, but may use other organic sub- 

 stances, though usuaily rather feebly. Some vibrios 

 attack cellulose ; thus V. agar liquefaciens (Microspora 

 agar liquefaciens) produces acetic and formic acids from 

 cellulose and also attacks agar. V . amylocella forms the 

 same products from cellulose, starch and dextrin. Cellu- 

 lose is also attacked by the sporing organisms Cellulo- 

 hacillus rnucosus and C. myxogenes. 



The anaerobic fermentations are used as sources of 

 j)ower gas and solvents from cellulose wastes and from the 

 decomposition of sewage sludge. Mineral salts are added 

 to the mash of w^ood pulp, sawdust, corn cobs, maize or 

 other plant residues, an inoculum of appropriate thermo- 

 philic organisms introduced, and fermentation allowed 

 to proceed at about 65° C. The conditions in the mash 

 soon become anaerobic. Hydrogen, methane and carbon 

 dioxide are produced together with some alcohol and 

 acetic acid, which is neutralised by calcium carbonate. 

 The carbon dioxide is separated from the gases and the 

 combustible gases used for lighting purposes or for 

 operating gas engines. The acetic acid is either re- 

 generated from the calcium acetate or the latter distilled 

 with formation of acetone. This process is extensively 

 operated in the " corn belt " of the United States, where 

 maize stalks and straw are partially fermented by 

 cellulose- and pectin-destroying organisms Avith production 

 of power gas and solvents ; the more resistant fibrous 

 parts of the stalk composing the vascular bundles are not 

 attacked, and are used for the manufacture of cardboard. 



The cellulose in plant wastes may also be partially 

 decomposed, giving combustible gases and leaving humin 

 which is used as a fertiliser, and the same applies to the 

 anaerobic fermentation of sewage, where the gaseous 

 products are again methane, hydrogen and carbon dioxide. 



