Dissertation > Industrial Technology > Chemical Industry > Other chemical industries > Fermentation industry > General issues

Continuous Fermentation of Pentose by Pichia Stipitis with Low-pH Treatments

Author JiGengSheng
Tutor YuShiYuan
School Nanjing Forestry University
Course Forest Chemical Process Engineering
Keywords Pichia stipitis Pentose fermentation Alcohol Low pH Processing Immobilized Yeast Cells
Type PhD thesis
Year 2004
Downloads 409
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Today's human society is facing major overpopulation, resource shortages, environmental pollution, energy shortages and other crises, including the energy problem is particularly severe. Humans need to get out from these crises, into an ideal path of sustainable development. In this process, including biotechnology, including the development and application of high technology will likely play an important role. Plant fiber materials include cellulose, hemicellulose and lignin, is the earth's most abundant bio-renewable resources, the use of sugar as a cheap source of fuel alcohol production is to solve the world's energy crisis, the most effective way. This paper studies the trunk Pichia (Pichia stipitis) growth and pentose fermentation law; through the establishment of steady-state continuous cultures of yeast were pentose fermentation carbon material balance and metabolic flow analysis; continuous fermentation of yeast in the free state of plant fiber Simulation materials hydrolyzate, based on the combined immobilization and low pH continuous fermentation process technology to solve the contamination problems. The main results are as follows: under the conditions of different nitrogen trunk Pichia growth and fermentation of xylose rule. The results show that the growth of ammonium sulfate and potassium nitrate is less effective as a nitrogen source, urea as a sole nitrogen source and yeast growth, the final concentration of the yeast used alone close to the time of peptone. Respectively, peptone, urea, ammonium sulfate and potassium nitrate as nitrogen source, to 40.0g / L xylose fermenting yeast Pichia trunk substrate, after 36h fermentation, alcohol concentrations were 17.29,15.07,13.76 and 13.46g / L ; ethanol yield with the theoretical yield ratio 97.30,94.79,78.03 and 84.84%, respectively. Studied the effects of trunk Pichia growth and fermentation are two important factors temperature and pH, using 30.0g / L xylose and 30.0g / L glucose syrup mixed carbon source for the proliferation, studies show that the trunk at pH Pichia 3.0 to 4.0 pH range of this lower still normal growth, but the final concentration and yield of yeast considerations Pichia tree growth optimum pH range of 4.6 to 5.8; yeast growth rate from consideration, and the optimum temperature range of 30 ~ 35 ℃. When using 40g / L xylose fermentation of xylose fermentation substrates, the results show that when the fermentation temperature is 35 ℃, pH value of 3.8 to 5.0 when the alcohol concentration in the fermentation broth higher; And when fermentation temperature is 25 ℃ , high alcohol concentration, and xylose utilization in the pH range 3.4 to 4.2. In different culture conditions, the trunk Pichia conducted two different dilution rate of continuous culture. In anaerobic continuous culture with 30.0g / L glucose as carbon source; continuous culture in limited supply of oxygen to 30.0g / L glucose and 15.0g / L of xylose as carbon source sugar mixture. The laws of both are the same, with the increase of dilution rate, the yeast concentration and decreasing alcohol concentration, the residual sugar concentration increased gradually; but yield different rates of alcohol, anaerobic continuous culture at a dilution rate of 0.14h -1 , the ethanol yield reached the maximum 1.110g / L · h; limited supply of oxygen under conditions when the dilution rate of 0.06h -1 , the maximum yield of alcohol 0.790g / L · h. It was also on the trunk Pichia were four stages of 400 h continuous chemostat at different stages of sugar fed different substrates formed four \analysis. The results showed that four \When the substrate is 15.0g / L xylose and 30.0g / L glucose mixed with sugar, the yeast fermentation metabolites after 41.19 percent of the carbon flow of alcohol; when the substrate is 30.0g / L xylose and 30.0g / L glucose sugar mixture inch, the value is only 34.46%. Studied the free trunk Pichia single-stage continuous fermentation, the dilution rate 0.08 h -1 down using a 2:1 ratio of glucose and xylose, total sugar mixed with different concentrations of sugar as substrate. The results showed that with increasing substrate concentration, the residual liquid spill total reducing sugar concentration has been increasing, but the rate of increase in the concentration of alcohol is not large; especially when the substrate concentration is greater than 60.09, yea, an alcohol concentration was maintained at 14.5 Qiao between .5 end, the theoretical yield of ethanol yields a ratio of 85.4% in the 79.8 range. This paper also studied the free trunk Pichia two series continuous fermentation. The results show that the bottom stream of the first speed is about 60.0n1L a small fermentation, in the stable phase (11 a clever days), 45.0 glL average sugar in the tank 1 32.35 pair was used, the average concentration of ethanol tank 1 12.36 pair, and the remaining 12.65 A pair of sugar continues to ferment in a tank 2 5.04 pair, two cans of alcohol concentration averaged 13.79 pair; in the bottom stream velocity is 45.Om successful first two continuous fermentation, in the stable phase (11 an 15 days), 45.0 Miao average sugar in the tank a few 34.379 was used, cans an alcohol concentration averaged H .429 few remaining 10.639 reducing sugar in the tank 2, a few continue to ferment a 6.319 average few, tank 2 .41 alcohol concentration averaged clever speaker. Free trunk experiment Pichia strain was fermented using clever .0 g / L xylose, and 30.0 g / L of glucose fermentation substrate mixture, a total of 22 days of two continuous fermentation, during a total of 3 tank 1 Different sub-processing of low pH. The results show that when the bottom stream velocity is 30 InL credits, although the continuous fermentation of yeast is free, but after two days of adaptation 1-fermentation, the fermentation tank 1 of the indicators are basically restored. Wherein the mean residual sugar concentration from the initial 8.52 glL 7.80,10.08 and ro.02 pair were changed, and accordingly, the concentration of alcohol, sugar utilization and ethanol yield is slightly decreased. Studied calcium alginate immobilized Pichia stipitis single-stage continuous fermentation, using two flow rates (O a 6 days: 45.0m balcony; 7 a 12 days: 67.5 mL small) stream plus 45.0 speaker substrate. Studies have shown that after only three days of fluctuations in the concentration of various substances fermenter has become constant, after three days of free yeast concentration, the concentration of reducing sugar, reducing sugar utilization, alcohol, ethanol yield with the theoretical ratio of the average A pair of values ??were 2.09, 7.89 secretin, 82.47%, and 84.84% Qiao .75 secretion. 7th day, increase speed bottom stream, the fermentation parameters of the fermenter reached steady state again soon. The last three days of free yeast concentration, reducing sugar concentration, sugar utilization, alcohol, ethanol yield and theoretical average values ??of the ratio of 1.88 pair, 10.509 / L, 76.67%, 14.34g / L and 52.35%. Finally, our results in a free trunk Pichia strain was fermented, with immobilized and low pH treatment technology for the continuous fermentation of sugar mixture of two series of studies, a total of

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