Development of Suitable Bio-Carrier for Continuous Ethanol Fermentation Using Sugarcane Bagasse
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Date
2019-10
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Addis Ababa University
Abstract
Cell immobilization has been proposed as an effective means of improving ethanol production. In this work, sugar cane bagasse as economically cheap and renewable was used as biofilm developmental carrier for saccharomyces cerevisiae ethanol production with cane molasses as a substrate. The aim of this thesis was to investigate the effect of cane preparation index (P.I.) and bagasse type; mill tandem bagasse (MTB) and cane diffuser bagasse (CDB) to cell retention then develop suitable bio-carrier for continuous ethanol production. The demand of ethanol per annum is increasing as the number of industries using ethanol as a solvent, fuel blending whereas distilleries production declined due to low fermentation efficiency. Hence the production of ethanol by fermentation technology has triggered us to investigate the best way and method which improve volumetric productivity. The CDB-immobilized bio-carrier was used for repeated batch fermentation, because CDB was with the highest cell retention from immobilization, the mass of cells retained on the carrier was quantified gravimetrically. From repeated batch fermentation overall results CDB of cane P.I. 87.5% was selected for continuous fermentation due to its highest stability. Continuous ethanol fermentation conducted in laboratory scale packed bed reactor and operating conditions (TRS and dilution rate) was optimized by using a central composite design (CCD) method. The optimum result which maximize ethanol volumetric productivity and ethanol yield were TRS 93.40 g/l, Dilution rate 0.91h-1 whereas the ethanol volumetric productivity and ethanol yield attained were 26.03g/lh and 0.474g/g respectively. The results have established the continuous ethanol fermentation with CDB at high cane P.I. (87.5%) with immobilized yeast cell reveals that the high dilution rate is favourable to the feed with low sugar concentration. For a high sugar concentration feed, the maximum sugar utilization can be achieved either by increasing bed height or by increasing number of columns.
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Keywords
Immobilization, sugarcane bagasse, saccharomyces cerevisiae, cane preparation index, Biofilm, Continuous ethanol fermentation