Instituto Politécnico Nacional, Centro de Investigación en Biotecnología Aplicada, Carretera Estatal Santa Inés Tecuexcomac-Tepetitla, km 1.5, 90700, Tepetitla de Lardizábal, Tlaxcala, Mexico.
Departamento de Ciencias, Instituto Nacional de Astrofísica, Óptica Y Electrónica, Luis Enrique Erro No.1, Santa María Tonantzintla, 72840, San Andrés Cholula, Puebla, Mexico.
Bioprocess Biosyst Eng. 2021 Sep;44(9):1923-1934. doi: 10.1007/s00449-021-02572-0. Epub 2021 Apr 21.
The most important parameter in bioprocesses is biomass, where not only the quantity produced in a culture but also the behavior that is presented are important concerns. It is clear that conditions of operation in a bioreactor affect biomass production, but how operation conditions affect the measurement of biomass on-line is of special interest. We studied the effect of bioreactor operating condition variations on model parameters using impedance spectroscopy for biomass monitoring. The model parameters analyzed were capacitance, resistance, alpha (α), conductivity delta (∆σ) and critical frequency (fc). These model parameters were obtained by fitting data from impedance measurements to an equivalent circuit model and Cole-Cole conductivity model. The effect of operating conditions on the medium with no cells was estimated by the percentage of change in each model parameter. The operating conditions with the most significant percentage of change were determined, by comparing to the percentage of change of the same model parameters obtained, during a fermentation of Bacillus thuringiensis as a cellular model. Equivalent circuit parameters were mainly affected by variation in pH, temperature and aeration, whereas Cole-Cole parameters were affected by variation in agitation, aeration, temperature and pH. Therefore, any variation in these operating conditions (within the test interval) during a fermentation may generate changes in monitoring parameters, which will not be a direct consequence of any change in the properties of the biomass.
在生物工艺中，最重要的参数是生物量，不仅要关注培养物中产生的数量，还要关注其表现出的特性。显然，生物反应器的操作条件会影响生物量的产生，但操作条件如何影响生物量的在线测量是特别值得关注的。我们使用阻抗谱法研究了生物反应器操作条件变化对生物量监测模型参数的影响。分析的模型参数有电容、电阻、α（α）、电导率增量（∆σ）和临界频率（fc）。这些模型参数是通过将阻抗测量数据拟合到等效电路模型和科尔-科尔电导率模型来获得的。通过比较在发酵过程中获得的相同模型参数的变化百分比，估计了无细胞介质中操作条件对每个模型参数的变化百分比的影响。通过比较发酵过程中苏云金芽孢杆菌作为细胞模型时相同模型参数的变化百分比，确定了具有最大变化百分比的操作条件。等效电路参数主要受 pH 值、温度和通气变化的影响，而科尔-科尔参数则受搅拌、通气、温度和 pH 值变化的影响。因此，发酵过程中这些操作条件（在测试区间内）的任何变化都可能导致监测参数的变化，而这些变化不会直接导致生物量特性的任何变化。
