PURPOSE: To obtain anaerobes having high cellulose decomposing activity by adding cellulose and vitamin to an aq. soln. of the materials constituting organisms, and culturing the anaerobes in a culture soln. freed of dissolved oxygen in the method for obtaining anaerobes to be used in the methane fermentation for treating org. waste.

CONSTITUTION: Cellulose and vitamin are added to an aq. soln. of the materials constituting organisms, dissolved oxygen is removed, and the soln. is transferred into a culture device in a gaseous mixture current. Sludge contg. microbes is inoculated into the soln., and the soln. is held at an appropriate temp. When the soln. is intermittently agitated, cellulose is decomposed, and gaseous methane and gaseous carbon dioxide are liberated. The culture soln. is exchanged, when the liberation of the gases is reduced. The process is repeated to obtain anaerobes having high cellulose decomposing activity. When the cellulose is decomposed by the anaerobes, the gas is liberated at the rate of about 0.5l/l tank volume per day.