Abstract
Fermentation engineering has played a pivotal role in modern industry for mass-producing chemicals, food additives, and medicines, with optimal culture conditions crucial for maximizing microbial growth and metabolite production. Thus, bacteria growth monitoring was crucial in fermentation processes, with current methods falling into two categories: off-line sampling and in-situ on-line monitoring. While off-line methods suffered from discrete monitoring points and potential pollution, current on-line methods faced limitations including an inability to distinguish living from dead cells and impurities and a lack of direct representation of metabolism. Carbon dioxide (CO2) levels, which closely correlated with chemical synthesis, could be measured with high sensitivity with Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology, enabling non-invasive, high-sensitivity detection of CO2 concentrations in microbial fermentation, offering a powerful tool for optimizing conditions and enhancing production efficiency. This study presented a novel approach to reveal the optimal culture conditions for Escherichia coli (E. coli) fermentation. Through the implementation of a custom metabolism monitoring system based on TDLAS technology in a simulated fermenter, alongside varied pH and temperature settings, we elucidated the influence of these factors on E. coli metabolism curves and calculated the growth rates via threshold times, identifying 38°C as the optimal temperature and pH 7.5 as the optimal pH. Integration of this spectroscopy method into fermenters held promise for enhanced in situ online real-time monitoring of metabolism in future fermentations.