ABSTRACT
The production of bio-ethanol from Elephant grass (Pennisetun purpureum) stem was carried out using elephant grass stem as a feedstock and a combination of Aspergillus niger at 0.2%(w/v) 0.4%(w/v), 0.6%(w/v), 0.8%(w/v) and 1%(w/v) concentrations and Saccharomyces cerevisiae (brewer's yeast) at 0.5% (w/v), 1%(w/v), 1.5%(w/v), 2%(w/v) and 2.5%(w/v) concentrations as cells by simultaneous saccharification and fermentation (SSF). The study determined the most suitable pre-treatment method from the following pretreatment methods; 1M H2SO4, 0.1M H2SO4, 1M NaOH, 0.2M NaOH, Boiling, and 3M NH4OH. IM NaOH pre-treatment gave the highest cellulose and lowest lignin content. The effects of temperature at 25oC, 30oC, 35oC, 40oC and 45oC; pH values of 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5; substrate concentration values of 1%(w/v), 2%(w/v), 3%(w/v), 4%(w/v) and 5%(w/v); particle size range of 53-106μm, 106-150μm, 150-250μm, 250-300μm and 300-425μm; and cell loading combination of Aspergillus niger at 0.2%(w/v) 0.4%(w/v), 0.6%(w/v), 0.8%(w/v), 1%(w/v) concentrations and Saccharomyces cerevisiae (brewer's yeast) at 0.5% (w/v), 1%(w/v), 1.5%(w/v), 2%(w/v), 2.5%(w/v) on the hydrolysis and fermentation process were investigated to obtain optimum conditions of fermentation. The optimum conditions of fermentation were obtained at temperature of 350C, pH value of 5.5, substrate concentration of 30g/l, particle size range of 250-300μm and Aspergillus niger to yeast ratio of 0.6/1.5 after 72 hours of fermentation time. Also substrate concentration of 30g/l, gave highest ethanol concentration of 23.4g/l and a yield of 78%. From the research, the kinetic Parameters which are reaction constant k and order of reaction n were evaluated to be 8.172x10-8l/g.s and 2 respectively.