pH 對 Clostridium acetobutylicum ATCC 824 於厭氧醱酵應答之影響

Effects of pH on the response of anaerobic fermentation of Clostridium acetobutylicum ATCC 824

陳譽升(Yu-sheng Chen)

指導教授 ： 賴龍山

朝陽科技大學/理工學院/應用化學系/碩士(2011年)

摘要

在 C. acetobutylicum 厭氧醱酵過程中，調控 pH值顯著影響醱酵應答，推測可能是藉由改變利用因而變更代謝途徑。舉例來說，在pHOverall 6試驗中，糖源在醱酵初期幾乎就已耗盡了；相對地，在沒有控制 pH 的實驗，在此時機其糖源利用率僅36％。
實驗中，當起始 pH值控制在範圍4.5至7.5間，與控制組相較、細胞產量減低(最低降為45％)；然而，若醱酵全程控制在 pHOverall 4.5，則細胞生長量卻增加了20％，此時，酸類代謝物延後生產而溶劑類代謝物則大幅減產。另一方面，在pHInitial 7.5的實驗中，研究發現酸類會延後約10 h 生產而溶劑產量降為48-67%；綜合以上結果：調控醱酵液 pH值會顯著地影響此菌株之醱酵型式等生化應答。此外，在血清瓶實驗中，丁酸/乙酸的比值 (即HBu/HAc) 與氣體總產量密切相關；然而，此比值在醱酵槽操作所扮演的角色仍不甚清楚。 在此厭氧醱酵、本研究發現：在調控醱酵液 pH值的實驗中，發現氧化還原電位 (ORP) 的讀數會因醱酵液 pH值之不同而變動若比對調控 pHInitial或 pHOverall實驗結果，它說明：本厭氧醱酵系統可能存在 pH-ORP 交互作用，特別在細胞對數生長期尤然。此外， ORP值之應答也可能被視為細胞對數生長之前或之後二個獨立的參數。

關鍵字

Clostridium 醱酵 ； ORP 應答 ； pH 調控

並列摘要

It was found that pH manipulation significantly influenced fermentation response of C. acetobutylicum, probably by changing nutrient utilization and then altering metabolic pathways. For example, sugar was almost depleted at earlier stages of the trial of pHOverall 6, whereas a 36% of sugar utilization was found at this timing when no pH manipulation was applied.
In experiments, biomass production was reduced and minimized to 45% when the initial pH was manipulated in the range of 4.5-7.5. Nevertheless, cell growth was increased by 20% in the trial of controlling pH 4.5 throughout the fermentation. In such a trial, acid production was shifted later, whereas solvent production was largely reduced. Moreover, acid production was postponed 10 h-later when the initial pH was manipulated at 7.5; meanwhile, solvent production was reduced by 48-67%. Therefore, the findings mentioned above described that fermentation type or biological response could be largely influenced by applying pH manipulation. Besides, the ratio of butyrate (HBu) to acetate (HAc) was closely related to total gas production in serum-bottle experiments; however, the role of such a ratio (HBu/HAc) in fermentor operations was not yet clear.
Under pH manipulation, the reading of ORP varied as the pH fluctuated in such an anaerobic fermentation. By manipulating pHInitial or controlling pHOverall, the difference of fermentation response described that pH-ORP interactions might probably be existed, especially in exponential growth phase of the fermentation. In addition, there was a possibility that the response of ORP could be viewed as two distinct parameters before or after exponential growth of the fermentation.

並列關鍵字

ORP response ； pH manipulation ； Clostridium fermentation

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