微量通氣對高濃度酒精醱酵之影響

Effect of aeration on the ethanol production by Saccharomyces cerevisiae in very-high-gravity(VHG) fermentation

簡萬山(WAN-SHAN CHIEN)

指導教授 ： 段國仁

大同大學/工程學院/生物工程學系所/碩士(2009年)

摘要

對酒精生產而言，控制醱酵液中的溶氧狀況是必要的，但傳統的溶氧電極（DO sensor）無法在較低溶氧值的情況下讀取有效值，因此無法對厭氧醱酵過程進行監測，而氧化還原電極（ORP sensor）給我們提供了一個新的精細監測手段，提供了利用監控醱酵液中微氧的變化，有效的控制酵母在醱酵階段所需的溶氧狀況，使用上較溶氧電極有彈性，而控制不同的ORP對於酵母的活性有重要的影響，對增強酒精轉化率（ethanol yield coefficient）和單位時間平均酒精生產速率（average ethanol productivity），以及降低殘糖濃度具有重要作用，對於酒精工業化生產而言具有重要意義。
利用以300、250及200 g/L不同濃度的葡萄糖批次酒精醱酵，各別利用通入微量空氣的方式有效控制ORP參數值於-150、-100 mV，以不控制ORP的實驗當對照組，共九組雙重複實驗之平均數據結果得知，ORP控制於-150 mV具有較佳之酒精轉化率，而ORP控制於-100 mV則有助於提高單位時間平均酒精生產速率，綜合衡量以上兩個因素之影響，利用250 g葡萄糖、ORP控制於-100 mV的實驗組具有較佳之表現，其酒精轉化率及單位時間平均酒精生產速率各為0.477、4.073 g/L/hr，比對照組之0.467、3.262 g/L/hr各提高了約2%及25%。
300 g/L的葡萄糖進行高濃度酒精醱酵時，利用於不同菌體生長階段通氣及不同的通氣量對生產酒精之影響，考量綜合各項因素之下，結果發現於菌體對數生長期（醱酵後8-18 hr）通入820 ml/min的空氣量，除了能保有與對照組相同之酒精轉化率（0.439）之外，並且能大幅提高其單位時間平均酒精生產速率（3.737 g/L/hr），為對照組（2.624 g/L/hr）的1.42倍。

關鍵字

氧化還原電位 ； 高濃度酒精醱酵 ； 通氣 ； 酵母菌

並列摘要

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.

並列關鍵字

Oxidation reduction potential (ORP) ； Very-high-gravity (VHG) ethanol fermentation ； Aeration ； Yeast (Saccharomyces cerevisiae)

參考文獻

周霖宏。2008。以葡萄糖為原料生產酒精之醱酵策略。大同大學生物工程研究所碩士論文。

黃禮彥。2008。以濃醪醱酵技術利用高梁生產酒精之研究。大同大學生物工程研究所碩士論文。

Attfield, P. V. 1987. Trehalose accumulates in Saccharomyces cerevisiae during exposure to agents that induce heat shock response. FEBS Lett. 225(1-2): 259-263.

Björkqvist, S., R. Ansell, L. Adler, and G. Lidén. 1997. Physiological response to anaerobicity of glycerol - 3 - phosphate dehydrogenase mutants of Saccharomyces cerevisiae. Appl. Environ. Microbiol. 63(1): 128- 132.

Devantier, R., S. Pedersen, and L. Olsson. 2005. Characterization of very high gravity ethanol fermentation of corn mash. Effect of glucoamylase dosage, pre-saccharification and yeast strain. Appl. Microbiol. Biotechnol. 68: 622 - 629.