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

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.