Horváth I S, Taherzadeh M J, Niklasson C, Lidén G
Department of Chemical Reaction Engineering, Chalmers University of Technology, S-412 96 Göteborg, Sweden.
Biotechnol Bioeng. 2001 Dec 5;75(5):540-9. doi: 10.1002/bit.10090.
Furfural is an important inhibitor of yeast metabolism in lignocellulose-derived substrates. The effect of furfural on the physiology of Saccharomyces cerevisiae CBS 8066 was investigated using anaerobic continuous cultivations. Experiments were performed with furfural in the feed medium (up to 8.3 g/L) using three different dilution rates (0.095, 0.190, and 0.315 h(-1)). The measured concentration of furfural was low (< 0.1 g/L) at all steady states obtained. However, it was not possible to achieve a steady state at a specific conversion rate of furfural, q(f), higher than approximately 0.15 g/g.h. An increased furfural concentration in the feed caused a decrease in the steady-state glycerol yield. This agreed well with the decreased need for glycerol production as a way to regenerate NAD+, i.e., to function as a redox sink because furfural was reduced to furfuryl alcohol. Transient experiments were also performed by pulse addition of furfural directly into the fermentor. In contrast to the situation at steady-state conditions, both glycerol and furfuryl alcohol yields increased after pulse addition of furfural to the culture. Furthermore, the maximum specific conversion rate of furfural (0.6 g/g.h) in dynamic experiments was significantly higher than what was attainable in the chemostat experiments. The dynamic furfural conversion could be described by the use of a simple Michaelis-Menten-type kinetic model. Also furfural conversion under steady-state conditions could be explained by a Michaelis-Menten-type kinetic model, but with a higher affinity and a lower maximum conversion rate. This indicated the presence of an additional component with a higher affinity, but lower maximum capacity, either in the transport system or in the conversion system of furfural.
糠醛是木质纤维素衍生底物中酵母代谢的重要抑制剂。采用厌氧连续培养法研究了糠醛对酿酒酵母CBS 8066生理特性的影响。在进料培养基中添加糠醛（最高8.3 g/L），以三种不同的稀释率（0.095、0.190和0.315 h⁻¹）进行实验。在所有获得的稳态下，测得的糠醛浓度都很低（<0.1 g/L）。然而，当糠醛的特定转化率q(f)高于约0.15 g/g·h时，无法达到稳态。进料中糠醛浓度的增加导致稳态甘油产量下降。这与作为再生NAD⁺的一种方式（即作为氧化还原汇发挥作用）对甘油生产需求的降低非常吻合，因为糠醛被还原为糠醇。还通过将糠醛直接脉冲添加到发酵罐中进行了瞬态实验。与稳态条件下的情况相反，向培养物中脉冲添加糠醛后，甘油和糠醇产量均增加。此外，动态实验中糠醛的最大特定转化率（0.6 g/g·h）明显高于恒化器实验中所能达到的转化率。动态糠醛转化可以用一个简单的米氏动力学模型来描述。稳态条件下的糠醛转化也可以用米氏动力学模型来解释，但具有更高的亲和力和更低的最大转化率。这表明在糠醛的运输系统或转化系统中存在一种具有更高亲和力但最大容量较低的额外成分。
