Optimizing the conditions of ethanol production from cassava and sweet potato

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Febuary, 2018
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Cassava and sweetpotato are root and tuber crops cultivated in Ghana that could serve as industrial raw material for ethanol production. Investigations were conducted to optimize the yield of ethanol from two (2) varieties each of Cassava and Sweetpotato. Response surface methodology was used to model the optimum liquefaction, saccharification and fermentation conditions for ethanol production from the cassava and sweetpotato varieties. Three starch hydrolytic enzymes (Liquozyme SC DS, Spirizyme Fuel, Viscozyme L) and two strains of yeast (Bio-Ferm XR, Baker’s yeast) were used for fermentation. The best liquefaction, saccharification and fermentation times established were 2.1 hours, 4 hours and 57.4 hours at 34oC respectively with Liquozyme SC DS, Spirizyme Fuel/Viscozyme L and Bio-Ferm XR (Lallemand) yeast. The combination of Viscozyme L and Spirizyme Fuel enzymes in a ratio of 1:1 was the best enzyme mix for saccharification for a duration of 4 hours. The yeast to employ for best fermentation was Bio-Ferm XR at temperature of 34oC for 57.4 hours duration. The results also indicated that 10 months matured Sika bankye and 3 months old Apomuden were the best cassava and sweetpotato varieties respectively for ethanol production. The best ethanol yield established from the study was 16.2% v/v from a 50:50 cassava:sweetpotato flour combination. Ethanol production with Sika bankye and Apomuden in a 50:50 ratio with GH¢ 119.00 as cost of fresh roots and tubers, ethanol yield of 15.5% v/v, selling price of GH¢ 4.7 per litre of ethanol and the use of a 10,000 litres per day capacity ethanol distilling plant generates net profit of between 11% and 31% over a period of five years. Ethanol production with cassava and sweetpotato is therefore a profitable venture.
A Thesis submitted to the Department of Food Science and Technology, Faculty of Biosciences, College of Science, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Science and Technology.