Abdel-Fattah Yasser R, Abdel-Fattah Wael R, Zamilpa Rogelio, Pierce James R
Department of Bioprocess Development, Genetic Engineering and Biotechnology Research Institute, Mubarak City for Scientific Research and Technology Applications, Alexandria, Egypt.
Acta Microbiol Pol. 2002;51(3):225-35.
Statistically designed experimental strategy has been performed in order to evaluate and optimize nutritional and environmental parameters that affect ferrous ion oxidation rate in Acidithiobacillus ferrooxidans ATCC 23270. Plackett-Burman design was carried out to evaluate efficiently the biological significance of 10 culture conditions influencing ferrous-ion oxidation rate of A. ferrooxidans grown for 5 days in shake-flask batch mode on the newly modified 9-K media. Among ten fermentation factors examined, the most significant variables influencing ferrous-ion oxidation rate were statistically elucidated to be pH and calcium nitrate as positive contributors, whereas trace metals solution and potassium chloride were the most significant negative contributors. The optimal levels of the most significant three nutritional factors were further predicted from a polynomial model created from the data obtained from three level factorial design, a Box-Behnken design. Predicted optimal ferrous-ion oxidation rate Q(Fe2+) was recorded to be 0.148 (g Fe2+/l/hr). On verifying the predicted value, an experiment was performed under optimal predicted conditions and showed an actual experimental Q(Fe2+) of 0.152 g/l/hr, which was 2.7% over the predicted value. Our optimized medium formula gave overall five folds increase in ferrous-ion oxidation rates over the previously published data of standard 9-K medium on batch culture of A. ferrooxidans ATCC 23270 with higher mu(max) (hr(-1)) of 0.177 which was achieved within 75 h incubation in shake-flask culture.
为了评估和优化影响氧化亚铁硫杆菌ATCC 23270中亚铁离子氧化速率的营养和环境参数，进行了统计设计的实验策略。采用Plackett-Burman设计来有效评估10种培养条件对在新改良的9-K培养基上摇瓶分批模式下生长5天的氧化亚铁硫杆菌亚铁离子氧化速率的生物学意义。在所研究的10个发酵因素中，经统计分析得出，影响亚铁离子氧化速率的最显著变量是pH值和硝酸钙，它们是正贡献因素，而痕量金属溶液和氯化钾是最显著的负贡献因素。根据从三水平析因设计（Box-Behnken设计）获得的数据建立的多项式模型，进一步预测了三个最显著营养因素的最佳水平。预测的最佳亚铁离子氧化速率Q(Fe2+)记录为0.148（g Fe2+/l/hr）。在验证预测值时，在预测的最佳条件下进行了实验，实际实验的Q(Fe2+)为0.152 g/l/hr，比预测值高出2.7%。我们优化后的培养基配方使亚铁离子氧化速率比之前发表的关于氧化亚铁硫杆菌ATCC 23270在分批培养标准9-K培养基的数据总体提高了五倍，在摇瓶培养75小时内达到了更高的最大比生长速率μ(max)（hr(-1)）为0.177。
