Study On Fuel Ethanol Production With Enzymatic Hydrolysis And Fermentation Of Acorn Starch

Fuel ethanol is a kind of renewable clean energy. Nowadays with energy supply and ecological environment worsens unceasingly, the development of fuel ethanol industry is priority in many countries as a kind of clean energy instead of oil. Therefore, seeking cheap and available biomass as fuel ethanol's raw fermentation materials has become a research hotspot at home and abroad.The forest fruits acorns were used as raw materials in the thesis. By double enzymatic hydrolysis and central composite design in Pachysolen tannophilus fermentation, acorns were hydrolyzed to glucose and then fermented to ethanol. Different influences of tannins to enzymes and Pachysolen tannophilus were also discussed so as to provide new fermentation materials and new technology.The physical properties of acorn starch were compared with them of corn and cassava starches which were used in fuel ethanol production by SEM diagram, X ray and viscosity analysis. Compared the particle shape and size,crystal structure and paste property of acorn starch with corn and cassava starch, we could conclude that the acorn starch was oval-shape. The particle size of it was smaller than the size of corn and cassava starch. The crystalline structure was C type. Otherwise, the corn and cassava starch were typically A crystal structure. The paste temperature was higher than corn and cassava starch. The overall paste property of acorn starch was similar to corn starch. Through these comparative studies we concluded that acorn starch could also be used in fuel ethanol production.Two-level factorial design was applied in optimizing the process of double enzymatic hydrolysis in acorn starch. By investigating the liquid-solid ratio, amylase dosage, liquefaction time, liquefaction temperature, glucoamylase dosage, saccharification time and temperature, we got the main factors amylase dosage, liquefaction time, glucoamylase dosage and saccharification time. Then the four main factors were optimized by orthogonal tests. Through analysis, the optimal conditions were: amylase dosage 50 U/g, liquefaction time 2 h, saccharification time 2 h, glucoamylase dosage 600 U/g. under these conditions the dextrose equivalent value of the acorn liquefied solution was 58.15 %. The ethanol production by Pachysolen tannophilus fermentation was optimized by 4-factors and 3-levels central composite design. Effects of fermentation time, inoculation, rotation speed and fermentation temperature on ethanol production were investigated and made a mathematical model according to the results. By investigating the ethanol concentration, the optimized technological parameters were as follows: fermentation time 68 h, inoculation 6 %, rotation speed 120 r/min and fermentation temperature 32℃. Under these conditions, the ethanol concentration was up to 20.58 g/L and 0.119 g/L residual glucose concentration. The adequacy of the model equation for predicting the optimum response values was verified effectively by the validation.Take regular water extraction to remove the tannins in acorns. Measure the residual tannin content according to different extraction times. With the increase in the number of extraction, the extraction time, the residual tannin content reduced gradually. Using the optimized double enzymatic hydrolysis craft hydrolyzed the acorn starch which was extracted for different times and contained different residual tannin content. We concluded from the hydrolysis that overall the glucose concentration increased as the increase of the extraction times which means there were inhibition to amylase and glucoamylase of tannin to some extent. Then using the optimized fermentation craft fermented the hydrolytic liquid by the two strains Pachysolen tannophilus and Saccharomyces cerevisiae. Through the comparison it could be concluded that there were also inhibition both to Pachysolen tannophilus and Saccharomyces cerevisiae. But the effect of inhibition is stronger to Saccharomyces cerevisiae than to Pachysolen tannophilus. That is, Pachysolen tannophilus showed more tannin tolerance than Saccharomyces cerevisiae.