Kongjan Prawit, Min Booki, Angelidaki Irini
Department of Environmental Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark.
Water Res. 2009 Mar;43(5):1414-24. doi: 10.1016/j.watres.2008.12.016. Epub 2008 Dec 24.
Biohydrogen production from xylose at extreme thermophilic temperatures (70 degrees C) was investigated in batch and continuous-mode operation. Biohydrogen was successfully produced from xylose by repeated batch cultivations with mixed culture received from a biohydrogen reactor treating household solid wastes at 70 degrees C. The highest hydrogen yield of 1.62+/-0.02 mol-H2/mol-xylose(consumed) was obtained at initial xylose concentration of 0.5 g/L with synthetic medium amended with 1g/L of yeast extract. Lower hydrogen yield was achieved at initial xylose concentration higher than 2g/L. Addition of yeast extract in the cultivation medium resulted in significant improvement of hydrogen yield. The main metabolic products during xylose fermentation were acetate, ethanol, and lactate. The specific growth rates were able to fit the experimental points relatively well with Haldane equation assuming substrate inhibition, and the following kinetic parameters were obtained: the maximum specific growth rate (mu(max)) was 0.17 h(-1), the half-saturation constant (K(s)) was 0.75g/L, and inhibition constant (K(i)) was 3.72 g/L of xylose. Intermittent N2 sparging could enhance hydrogen production when high hydrogen partial pressure (> 0.14 atm) was present in the headspace of the batch reactors. Biohydrogen could be successfully produced in continuously stirred reactor (CSTR) operated at 72-h hydraulic retention time (HRT) with 1g/L of xylose as substrate at 70 degrees C. The hydrogen production yield achieved in the CSTR was 1.36+/-0.03 mol-H2/mol-xylose(sonsumed), and the production rate was 62+/-2 ml/d x L(reactor). The hydrogen content in the methane-free mixed gas was approximately 31+/-1%, and the rest was carbon dioxide. The main intermediate by-products from the effluent were acetate, formate, and ethanol at 4.25+/-0.10, 3.01+/-0.11, and 2.59+/-0.16 mM, respectively.
研究了在极端嗜热温度（70摄氏度）下从木糖生产生物氢的分批和连续模式操作。通过从处理70摄氏度家庭固体废物的生物氢反应器接收的混合培养物进行重复分批培养，成功地从木糖生产了生物氢。在初始木糖浓度为0.5 g/L且添加1g/L酵母提取物的合成培养基中，获得了最高氢产率1.62±0.02 mol-H2/mol-木糖（消耗）。初始木糖浓度高于2g/L时，氢产率较低。在培养基中添加酵母提取物可显著提高氢产率。木糖发酵过程中的主要代谢产物是乙酸、乙醇和乳酸。假设存在底物抑制，比生长速率能够用Haldane方程较好地拟合实验点，并获得了以下动力学参数：最大比生长速率（μ(max)）为0.17 h(-1)，半饱和常数（K(s)）为0.75g/L，抑制常数（K(i)）为3.72 g/L木糖。当分批反应器顶部空间存在高氢分压（> 0.14 atm）时，间歇N2鼓泡可提高产氢量。在70摄氏度下，以1g/L木糖为底物，在水力停留时间（HRT）为72小时的连续搅拌反应器（CSTR）中可成功生产生物氢。CSTR中的产氢率为1.36±0.03 mol-H2/mol-木糖（消耗），生产率为62±2 ml/d x L（反应器）。无甲烷混合气体中的氢含量约为31±1%，其余为二氧化碳。流出物中的主要中间副产物分别为乙酸、甲酸和乙醇，浓度分别为4.25±0.10、3.01±0.11和2.59±0.16 mM。
