The effect of hydrogen acceptors on the kinetic parameters of D-xylose fermentation under anaerobic conditions was studied in a transient culture of immobilized Pachysolen tannophilus cells. Addition of oxygen to a steady-state culture resulted in a rapid increase (up to fivefold) in the rates of ethanol production and D-xylose uptake, but the rate of xylitol production was unaffected. Furthermore, the molar ethanol yield increased from 0.97 to 1.43 in the presence of oxygen. The moles of ethanol produced per moles of oxygen utilized were considerably greater than would be predicted from the stoichiometry of D-xylose fermentation, which suggests that the organism required oxygen for other functions in addition to its role as a hydrogen acceptor in D-xylose metabolism. When the artificial hydrogen acceptors acetone, acetaldehyde, and acetoin were added to the culture, the rate of ethanol production increased while the xylitol production rate decreased but the rate of xylose uptake was unaffected. The molar ethanol yields increased from 1.03 to 1.63, 1.43, and 1.24 upon addition of acetaldehyde, acetone, and acetoin, respectively, at the expense of the molar xylitol yields. The hydrogen acceptors sodium acetate, methylene blue, benzyl viologen, phenazine methosulfate, indigo carmine, and tetrazolium chloride had no effect on ethanol production.

译文

在固定化的Pachysolen tannophilus细胞的瞬时培养中,研究了氢受体对厌氧条件下D-木糖发酵动力学参数的影响。向稳态培养物中添加氧气会导致乙醇产生和D-木糖吸收的速率迅速增加 (高达五倍),但木糖醇产生的速率不受影响。此外,在氧存在下,摩尔乙醇产率从0.97增加到1.43。每摩尔使用的氧气产生的乙醇摩尔比D-木糖发酵的化学计量所预测的要大得多,这表明该生物除了在D-木糖代谢中充当氢受体外,还需要氧气来发挥其他功能。当将人工氢受体丙酮,乙醛和乙酰丁添加到培养物中时,乙醇的产生速率增加,而木糖醇的产生速率降低,但木糖的吸收速率不受影响。在添加乙醛、丙酮和乙妥英后,摩尔乙醇产率分别从1.03增加到1.63、1.43和1.24,但牺牲摩尔木糖醇产率。氢受体乙酸钠,亚甲基蓝,苄基紫精,吩嗪硫酸酯,靛蓝胭脂红和氯化四唑对乙醇生产没有影响。

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