Chair of Brewing and Beverage Technology, TUM School of Life Sciences, Technical University of Munich, 85354 Freising, Germany.
Sensors (Basel). 2024 Sep 27;24(19):6271. doi: 10.3390/s24196271.
In fermentation processes, changes in yeast cell count and substrate concentration are indicators of yeast performance. Therefore, monitoring the composition of the biological suspension, particularly the dispersed solid phase (i.e., yeast cells) and the continuous liquid phase (i.e., medium), is a prerequisite to ensure favorable process conditions. However, the available monitoring methods are often invasive or restricted by detection limits, sampling requirements, or susceptibility to masking effects from interfering signals. In contrast, ultrasound measurements are non-invasive and provide real-time data. In this study, the suitability to characterize the dispersed and the liquid phase of yeast suspensions with ultrasound was investigated. The ultrasound signals collected from three commercially available yeast were evaluated and compared. For all three yeasts, the attenuation coefficient and speed of sound increased linearly with increasing yeast concentrations (0.0-1.0 wt%) and cell counts (R > 0.95). Further characterization of the dispersed phase revealed that cell diameter and volume density influence the attenuation of the ultrasound signal, whereas changes in the speed of sound were partially attributed to compositional variations in the liquid phase. This demonstrates the ability of ultrasound to monitor industrial fermentations and the feasibility of developing targeted control strategies.
在发酵过程中，酵母细胞计数和底物浓度的变化是酵母性能的指标。因此，监测生物悬浮液的组成，特别是分散的固相（即酵母细胞）和连续的液相（即培养基），是确保有利的工艺条件的前提。然而，现有的监测方法通常具有侵入性，或者受到检测极限、采样要求或对干扰信号掩蔽效应的敏感性的限制。相比之下，超声测量是非侵入性的，并提供实时数据。在这项研究中，研究了用超声对酵母悬浮液的分散相和液相进行特征描述的适用性。评估和比较了从三种市售酵母收集的超声信号。对于所有三种酵母，衰减系数和声速随酵母浓度（0.0-1.0 wt%）和细胞计数（R > 0.95）的增加呈线性增加。对分散相的进一步特征描述表明，细胞直径和体积密度影响超声信号的衰减，而声速的变化部分归因于液相的组成变化。这证明了超声监测工业发酵的能力和开发有针对性的控制策略的可行性。
