THE EFFECT OFSEQUENTIALALKALI AND ACID PRE TREATMENTSONBIOETHANOLPRODUCTION FROMPartheniumhysterophorusL. USING Saccharomyces cerevisiae

Abstract

Lignocellulosic biomass is one of the most suitable alternative energy sources, whichcan be harnessed to meet the challenges of energy security. Energy resources such as petroleum and coal are being utilized at a rapid rate and eventually run out. Therefore, this research was initiated to find an alternative substrate for the production of ethanol from a cost-effective substrate. Parthenium leaf and stem were collected from Haramaya University. The collected Parthenium leaf and stem washed and dried in an oven and ground to powder form by a grinding machine. The powders of Parthenium leaf and stem with different concentrations (50gm, 60gm, 70gm, and 80gm) were treated with sodium hydroxide (alkali pre-treatment). The inocula(1% and 2% Saccharomyces cerevisiae) with 100ml nutrient solution were added to each substrate concentration separately and the pH of the solution was adjusted to 4.5 and allowed to ferment for 15days at 30OC to determine cell denity, reucing sugar and for ethanol production. In this study, the highest cell density was observed on the 9th day of the fermentation period with 60grams of substrate inoculated at 2% inoculum concentration. The cell density decreased gradually as the fermentation period increased. Maximum bio-ethanol production of pre-treated Parthenium leaf and stem (22.50%) was achieved on the 9th day of fermentation from 60gm of substrate inoculated with 2% yeast suspension. Moreover, on the 3rd day of the fermentation period, the highest reducing sugar concentration (27.75mg/ml) was obtained from 60gm of alkali pre-treated substrate inoculated with 2% Saccharomyces cerevisiae, whereas the same substrate concentration showed 20.22mg/ml in the untreated substrate. Within time of fermentation, the bio-ethanol yield and cell density also increased up to the 9th day of the fermentation. In this study, the effect of alkali pre-treatment on bio-ethanol production was also examined. The result showed that a 60-gram substrate with 2% Saccharomyces cerevisiae showed as optimum for ethanol production and the alkali pre-treated samples yielded more ethanol than the untreated samples.