Production of bioethanol from liquid waste from cassava dough during gari processing

摘要

Starch is a polysaccharide that can be hydrolyzed by enzymes and fermented into bioethanol. It is commonly found in Ghana as the effluent during cassava-gari processing. The copious amount and its related stench in the environment as effluent have necessitated its conversion into ethanol. This present study investigated bioethanol production by enzyme catalysis using effluent from cassava dough during gari processing. The starch was converted to dextrins using alpha-amylase enzymes extracted from paddy rice after which glucoamylase extracted from Aspergillus niger was used to hydrolyze the dextrins to glucose. The glucose was subsequently fermented into ethanol using yeast, and the ethanol was recovered by fractional distillation. The optimum temperature and pH of the enzymes applied were investigated. Hence, the optimum pH and temperature for the alpha-amylase during the starch liquefaction was 4 and 60 degrees C, respectively, while that of the glucoamylase for the starch saccharification was 3.5 and 60 degrees C, respectively. The average ethanol yield was 26.5 +/- 0.15% v/v, and the distillate purity was determined as 65.33 +/- 0.58%. This suggests that bioethanol production from the starch effluent of cassava dough during gari processing by enzyme catalysis may be employed industrially in addition to the conventional acid enzyme catalysis if the process is fully optimized.