Institut National des Sciences Appliquées, UPS, INP, Laboratoire Ingénierie des Systèmes Biologiques et Procédés, Université de Toulouse, 135 Avenue de Rangueil, Toulouse, France.
J Ind Microbiol Biotechnol. 2010 May;37(5):437-45. doi: 10.1007/s10295-009-0688-7. Epub 2010 Jan 12.
Carbon distribution and kinetics of Candida shehatae were studied in fed-batch fermentation with xylose or glucose (separately) as the carbon source in mineral medium. The fermentations were carried out in two phases, an aerobic phase dedicated to growth followed by an oxygen limitation phase dedicated to ethanol production. Oxygen limitation was quantified with an average specific oxygen uptake rate (OUR) varying between 0.30 and 2.48 mmolO(2) g dry cell weight (DCW)(-1) h(-1), the maximum value before the aerobic shift. The relations among respiration, growth, ethanol production and polyol production were investigated. It appeared that ethanol was produced to provide energy, and polyols (arabitol, ribitol, glycerol and xylitol) were produced to reoxidize NADH from assimilatory reactions and from the co-factor imbalance of the two-first enzymatic steps of xylose uptake. Hence, to manage carbon flux to ethanol production, oxygen limitation was a major controlled parameter; an oxygen limitation corresponding to an average specific OUR of 1.19 mmolO(2) g DCW(-1) h(-1) allowed maximization of the ethanol yield over xylose (0.327 g g(-1)), the average productivity (2.2 g l(-1) h(-1)) and the ethanol final titer (48.81 g l(-1)). For glucose fermentation, the ethanol yield over glucose was the highest (0.411 g g(-1)) when the specific OUR was low, corresponding to an average specific OUR of 0.30 mmolO(2) g DCW(-1) h(-1), whereas the average ethanol productivity and ethanol final titer reached the maximum values of 1.81 g l(-1) h(-1) and 54.19 g l(-1) when the specific OUR was the highest.
用木糖或葡萄糖（分别）作为碳源，在矿质培养基中进行分批补料发酵，研究了 Candida shehatae 的碳分布和动力学。发酵分为两个阶段，有氧阶段专门用于生长，然后是氧气限制阶段，专门用于生产乙醇。用平均比耗氧速率（OUR）来量化氧气限制，OUR 变化范围为 0.30 至 2.48mmolO2 g 干细胞重量（DCW）（-1）h（-1），这是有氧转变前的最大值。研究了呼吸、生长、乙醇生产和多元醇生产之间的关系。结果表明，生产乙醇是为了提供能量，而多元醇（阿拉伯糖醇、赤藓糖醇、甘油和木糖醇）则是为了重新氧化同化反应和木糖摄取的两个初始酶步骤的辅酶失衡产生的 NADH。因此，为了控制碳流到乙醇生产，氧气限制是一个主要的控制参数；平均比 OUR 为 1.19mmolO2 g DCW（-1）h（-1）的氧气限制允许最大限度地提高木糖的乙醇产率（0.327gg（-1）），平均生产力（2.2gL（-1）h（-1））和乙醇最终浓度（48.81gL（-1））。对于葡萄糖发酵，当 OUR 较低时，葡萄糖的乙醇产率最高（0.411gg（-1）），对应的平均 OUR 为 0.30mmolO2 g DCW（-1）h（-1），而当 OUR 最高时，乙醇的平均生产力和乙醇最终浓度达到最大值，分别为 1.81gL（-1）h（-1）和 54.19gL（-1）。
