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URN etd-0907109-020347 Statistics This thesis had been viewed 2275 times. Download 1292 times. Author WAN-SHAN CHIEN Author's Email Address No Public. Department Bioengineering Year 2008 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 118 Title Effect of aeration on the ethanol production by Saccharomyces cerevisiae in very-high-gravity(VHG) fermentation Keyword Yeast (Saccharomyces cerevisiae) Aeration Very-high-gravity (VHG) ethanol fermentation Oxidation reduction potential (ORP) Oxidation reduction potential (ORP) Very-high-gravity (VHG) ethanol fermentation Aeration Yeast (Saccharomyces cerevisiae) Abstract Controlling the level of dissolved oxygen in fermenting medium is essential in ethanol production. Since the traditional DO sensor failed to monitor anaerobic fermentation by detecting the significant value at low amount of dissolved oxygen, ORP sensor was utilized as a new delicate method to monitor the slight change of oxygen level, furthermore, to control the level of dissolved oxygen during yeast fermentation. Comparing to DO sensor, ORP sensor offered more flexibility and the management to control different ORP levels which played a significant role in ethanol industry by increasing activity of yeast, enhancing ethanol yield coefficient and average ethanol productivity, and reducing residual glucose concentration.
Nine groups of ethanol fermentation studies were conducted using glucose baths of the concentrations of 300, 250, and 200 g/L, parameters of ORP -150, -100 mV by injecting slight different amount of air and uncontrolled ORP as negative control group. The results showed the best ethanol yield coefficient was achieved at -150 mV of ORP, and average ethanol productivity was increased at -100 mV of ORP. Taken both factors into consideration, the group using 250 g/L glucose with -100 mV of ORP had better performance, in which the ethanol yield coefficient was increased by 2% to 0.477, comparing to that of control group 0.467. Average ethanol productivity was increased by 25% to 4.073 g/L/hr, comparing to that of the control group 3.262 g/L/hr.
During very-high-gravity ethanol fermentation using 300 g/L glucose, considering the influence of aeration in different phases of yeast growth and the different injection levels of air on the productivity of ethanol, it was found in log phase of cell growth (after 8-18 hr fermentation), with 820 ml/min air injection, ethanol yield coefficient maintained the same as that of control group (0.439) and average ethanol productivity was increased by 142 % to 3.737 g/L/hr, comparing to that of the control group 2.624 g/L/hr.
Advisor Committee Kow-Jen Duan - advisor
Chi-Hsien Liu - co-chair
Ming-Tse Lin - co-chair
Files Date of Defense 2009-07-31 Date of Submission 2009-09-07