Schenk Jonas, Marison Ian W, von Stockar Urs
Laboratory of Chemical and Biological Engineering, Ecole Polytechnique Fédérale de Lausanne, CH J2 503, Station 6, CH-1015 Lausanne, Switzerland.
Biotechnol Bioeng. 2008 May 1;100(1):82-93. doi: 10.1002/bit.21719.
An on-line pH monitoring method based on mid-infrared spectroscopy relevant to bioprocesses is presented. This approach is non-invasive and does not require the addition of indicators or dyes, since it relies on the analysis of species of common buffers used in culture media, such as phosphate buffer. Starting with titrations of phosphoric and acetic acid solutions over almost the entire pH range (2-12), it was shown that the infrared spectra of all samples can be expressed as a linear combination of the molar absorbance of the acids and their deprotonated forms. In other words, pH had no direct influence on the molar infrared spectra themselves, but only on deprotonation equilibria. Accurate prediction (standard error of prediction for pH < 0.15 pH units) was achieved by taking into account the non-ideal behavior of the solutions, using the Debye-Hückel theory to estimate the activity coefficients. Batch cultures of E. coli were chosen as a case study to show how this approach can be applied to bioprocess monitoring. The discrepancy between the spectroscopic prediction and the conventional electrochemical probe never exceeded 0.12 pH units, and the technique was fast enough to implement a feedback controller to maintain the pH constant during cultivation.
提出了一种基于中红外光谱的与生物过程相关的在线pH监测方法。这种方法是非侵入性的，不需要添加指示剂或染料，因为它依赖于对培养基中常用缓冲液（如磷酸盐缓冲液）成分的分析。从几乎整个pH范围（2 - 12）对磷酸和乙酸溶液进行滴定开始，结果表明所有样品的红外光谱都可以表示为酸及其去质子化形式的摩尔吸光度的线性组合。换句话说，pH对摩尔红外光谱本身没有直接影响，而仅对去质子化平衡有影响。通过考虑溶液的非理想行为，利用德拜 - 休克尔理论估计活度系数，实现了准确的预测（pH预测标准误差 < 0.15 pH单位）。选择大肠杆菌的分批培养作为案例研究，以展示这种方法如何应用于生物过程监测。光谱预测与传统电化学探头之间的差异从未超过0.12 pH单位，并且该技术足够快，可以实施反馈控制器以在培养过程中保持pH恒定。
