STUDYING THE OPTIMAL CONDITIONS FOR GLUCOSE AND BIO-ETHANOL PRODUCTION FROM SPIROGYRA AFRICANA

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Department of Engineering

ABSTRACT
In this research work, the optimal conditions for glucose and bio-ethanol production from Spirogyra africana were studied. The Spirogyra africana samples collected from the Ahmadu Bello University Zaria Dam were dried, milled and sieved to ≤ 125 μm, and subsequently analyzed for carbohydrate content. Prior to hydrolysis, a set of the samples was pre-treated with NaOH, 0.5, 1.0 and 2.0 % (w/v), another set was blanched for 5 minutes at different temperatures (30 oC to 100 ºC), while another set served as control (untreated). Aspergillus niger and Saccharomyces cerevisiae were used for saccharification and fermentation processes, respectively. Untreated biomass sample at two (2) days of hydrolysis with glucose yield of 29.13 wt/wt % was chosen as ideal for saccharification in this study. The result from the proximate analysis showed that Spirogyra africana contains 39.72 % carbohydrate. On the first day of hydrolysis, the blanched sample gave a relatively superior glucose yield of 15.94 wt/wt % in comparison to the values of 14.33 and 12.03 wt/wt % for NaOH treated sample and the control, respectively. However, on the second day, the glucose yield from the three set ups (blanched, NaOH treated and the control) all gave a comparative glucose yield of 29.15, 29.41 and 29.13 wt/wt %, respectively. Only marginal increments were recorded on the third day, corresponding to 30.72, 32.28 and 30.66 wt/wt % respectively. The optimum Saccharification conditions obtained in this work were: reaction temperature of 25-30 oC, pH of 4.5, residence time of 48 hrs., substrate concentration of 50 g/l and A. niger concentration of 0.6 % (w/v). Similarly, the optimal conditions for the fermentation were: reaction temperature of 35 oC, pH of 5.5, reaction time of 72 hrs., and yeast concentration of 1.0 % (w/v), which gave a bio-ethanol yield of 21.4 % (v/v).