The conversion, use and access to energy are among the great challenges of our time, including sustainability, environmental quality, safety and quality of life. Cellulose is the most abundant renewable natural biological source on the planet and the use of products and bioenergy based on the lignocellulosic matrix, at low costs, is important for the sustainable development of human beings. Therefore, the biodegradation of cellulose by microrganisms-produced cellulase enzymes or cellulosomes (which are complexes of several cellulases) accounts for the largest carbon flux from the fixed carbon of atmospheric CO2. However, the use of lignocellulosic material for the production of ethanol from the enzymatic hydrolysis of the pre-treated material has as technical and economic barriers the cost and the enzyme production technology itself. This project aimed to explore the existing biota in a dairy cattle effluent treatment system with a view to selecting cellulolytic microorganisms as a potential alternative to the difficulties associated with the use of enzymes. The experiment was carried out with a New Brunswick Scientific bioreactor, with a working volume of 0.9 liters. The fermentation medium was obtained by sterilizing the effluent from the waste treatment system of Embrapa Dairy Cattle, located in the town of Coronel Pacheco, State of Minas Gerais. Inoculation of the bioreactor was carried out with the effluent obtained before the separation sieve step (raw effluent/with solids), with a final operating dilution between 105 and 106 CFU/mL (i.e. Colony Forming Units/milliliter of sample). Sample collection (10 mL) was initially performed at the following time intervals: zero, 6 hours, 12 hours, 18 hours, 24 hours, 30 hours and 36 hours consecutively in order to construct a growth curve of microorganisms. These samples were used for enumeration and isolation of microorganisms. To select/develop potentially cellulolytic microorganisms, a second phase of the experiment was carried out. The bioreactor was filled with the same substrate added with cellulose and inoculum. Five concentrations of 0.5 to 2% of appropriate cellulose preparations were tested, like the microcrystalline form. In the physicochemical analysis, the content of dry matter, crude protein, neutral and acid detergent fiber, cellulose, hemicellulose and lignin, and fractions of nitrogen and carbohydrates were determined. After microbiological analysis, the organisms chosen as possible cellulose degraders were characterized morphologically and physiologically, as well as biochemically, for further identification according to genus and species.