Investigation On The Production Of Ethanol From Cassava Pulp By Separate Hydrolysis And Fermentation And Simulataneous Saccharification And Fermentation

Ethanol fuel is made by fermentation and distillation from corn, potato, sugarcane orother plants. The rising price of oil promotes the vigorous development of the global biofuelethanol industry. Cassava pulp is a solid waste from cassava starch manufacture, with hugeannual output and high contents of starch and lignocelluloses, attracting the increasing focuson its recovery. In the present study, attempts to improve ethanol fermentation from cassavapulp were conducted by Saccharomyces cerevisiae in both Separate hydrolysis andfermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF).Moisture content of wet cassava pulp was 83.12%, with pH value 3.4. The maincompositions of dry cassava pulp were ash 2.84%, cellulose 11.40%, starch content 40.12%,hemicellulose content 8.29%, protein content 4.43%, and fa t content 3.45%. The resultsshowed that the optimal enzymatic hydrolysis conditions were pH 5.0, 50℃, cellulase loading15 FPU/g cellulose, Novozyme 188 loading 30 U/g cellulose, Amylase loading 500 IU/gstarch, AMG loading 500 IU/g starch, and initial substrate concentration of 4% (w/v), inwhich released glucose can reach 74.4%. For fed-batch process, the released glucose of 72.4%was reached, which was 18% higher than that of batch process with the initial substrateconcentration of 16% (w/v). The released glucose for enzymes feeding was 61.2%.The optimum conditions of SSF were 37℃, pH value of 5.0 and inoculum size of 6%.Under the optimum conditions, the ethanol concentration and fermentation efficiency were7.71 g/L and 70.76%, respectively, with the substrate concentration of 4%. The ethanolconcentration and fermentation efficiency reached 34.67 g/L and 63.60%, respectively, at thesubstrate concentration of 20% (w/v).The nitrogen supplementation did not result in significant effect on the fermentation atthe substrate concentration of 4%. However, when the substrate concentration was as high as16%, 5.2% higher fermentation efficiency was observed with nitrogen supplementation andthe ethanol concentration of 26.3 g/L was reached.Compared with the batch process, the fed-batch culture greatly improved ethanolproduction and fermentation efficiency, with 40.12 g/L and 71.39% respectively . While in thefed-batch culture, ethanol production of 43.25 g/L and fermentation efficiency of 76.96% were reached with enzymes feeding.