Cassava roots: perspectives of a traditional staple for bio-solvents production

The culture media prepared from mashed cassava and cassava starch were used to test their convertibility into organic solvents such as acetone, butanol, and ethanol. The trials were conducted in Erlenmeyer flasks containing various culture media with initial starch concentrations ranging from 30 g/l to 100 g/l. Fermentation was carried out by Clostridium acetobutylicum DSM 1731. The purpose of these tests was to determine the initial starch concentration which could be used as a starting point for the fermentation in laboratory bioreactors. In this case, we used two culture media: the first one made with cassava starch (M1), and the second one with mashed fresh cassava (M2). The culture media were supplemented with organic and inorganic nutrients. Fermentation in M1 medium resulted in the production of 17.8 g/l solvents, i.e. 12.3 g/l butanol, 3.7 g/l acetone, and 1.8 g/l ethanol, while in M2 it provided 16.2 g/l solvents representing approximately 11.4 g/l of butanol, 3.0 g/l of acetone, and 1.8 g/l of ethanol. The optimum production of butanol in M1 was 12.3 g/l in 96 h of fermentation, which is a low yield of 25% and 0.13 g/l/h productivity. Although the fermentation in medium M2 was also low (with 11.4 g/l butanol optimally), it allowed to save on the nutrient supply since it was done without the addition of minerals and organic substances.