Production of Bioethanol from Cassava using Zymomonas mobilis: Effect of Temperature and Substrate concentration

Abstract

The production of ethanol from cassava flour using Zymomonas mobilis a gram negative bacterium was conducted at 30oC, 33oC, 35oC and 37oC. The fermentation reaction was also carried out at different substrate concentrations; 5% W/V, 7% W/V and 10% W/V. The microorganism Zymomonas mobilis was detected in palm wine, isolated and identified. It was found to be gram negative, oxidase negative, catalase positive, anaerobic and plump rods with an unusual width. Results obtained from the simultaneous saccharification and fermentation reactions carried out with Zymomonas mobilis showed that maximum theoretical ethanol yield of 63% was obtained for 7% W/V cassava flour at 35oC. This was followed by a theoretical yield of 56.23 and 54.12 for 5% W/V and 10% W/V cassava flour, respectively. Fermentations at 30oC and 33 oC gave similar results with 7% W/V cassava producing higher ethanol yield when compared to 5% W/V and 10% W/V. Fermentation reactions at 37oC gave the lowest ethanol yields. The optimum pH for the simultaneous saccharification and fermentation of cassava was found to be pH of 6.