[en] The growing costs of the raw materials coming from the petroleum, base of the processes of acetone and butane, they have originated a renovated interest for the fermentative processes. These processes stopped to be applied in 1930 by their unfavorable economic conditions in comparison with the synthetic processes. The Institute of Biotechnology of the National University of Colombia, after considering that the country imports annually around 2500 tons of butanol and 80% of acetone, began in 1987 a program of development of the acetobutilic fermentation starting from cane molasses. In accordance with the study of economic pre feasible for the butanol and acetone production for fermentation, of Serrano and Pinzon, the gases constitute 83% of the total revenues received by sales, while the solvents, ethanol, butanol and acetone, only 16%, reason for which is necessary the evaluation of the gases produced in the fermentation