Biomass Refinery Research Center (BRRC), National Institute of Advanced Industrial Science and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
Appl Biochem Biotechnol. 2012 Dec;168(8):2094-104. doi: 10.1007/s12010-012-9920-4. Epub 2012 Oct 18.
The inhibitory effects of pH and acetic acid on the co-fermentation of glucose and xylose in complex medium by recombinant flocculent Saccharomyces cerevisiae MA-R4 were evaluated. In the absence of acetic acid, the fermentation performance of strain MA-R4 was similar between pH 4.0-6.0, but was negatively affected at pH 2.5. The addition of acetic acid to batch cultures resulted in negligible inhibition of several fermentation parameters at pH 6.0, whereas the interactive inhibition of pH and acetic acid on the maximum cell and ethanol concentrations, and rates of sugar consumption and ethanol production were observed at pH levels below 5.4. The inhibitory effect of acetic acid was particularly marked for the consumption rate of xylose, as compared with that of glucose. With increasing initial acetic acid concentration, the ethanol yield slightly increased at pH 5.4 and 6.0, but decreased at pH values lower than 4.7. Notably, ethanol production was nearly completely inhibited under low pH (4.0) and high acetic acid (150-200 mM) conditions. Together, these results indicate that the inhibitory effects of acetic acid and pH on ethanol fermentation by MA-R4 are highly synergistic, although the inhibition can be reduced by increasing the medium pH.
评估了 pH 值和乙酸对重组絮状酿酒酵母 MA-R4 在复杂培养基中协同发酵葡萄糖和木糖的抑制作用。在没有乙酸的情况下，菌株 MA-R4 在 pH 值 4.0-6.0 之间的发酵性能相似，但在 pH 值 2.5 时受到负面影响。在 pH 值 6.0 的分批培养中添加乙酸，对几种发酵参数几乎没有抑制作用，而在 pH 值低于 5.4 时，观察到 pH 值和乙酸对最大细胞和乙醇浓度、糖消耗和乙醇生产速率的交互抑制作用。与葡萄糖相比，乙酸对木糖消耗速率的抑制作用尤为显著。随着初始乙酸浓度的增加，在 pH 值 5.4 和 6.0 下，乙醇产率略有增加，但在 pH 值低于 4.7 时下降。值得注意的是，在低 pH（4.0）和高乙酸（150-200mM）条件下，乙醇生产几乎完全受到抑制。总之，这些结果表明，尽管通过提高培养基 pH 值可以减轻抑制作用，但乙酸和 pH 值对 MA-R4 乙醇发酵的抑制作用具有高度协同性。
