Harnessing Raman Spectroscopy for Enhanced Bioprocess Monitoring: Predictive CO₂ Analysis and Robust pH Determination in Bioreactor Off-Gas Stream

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript(3597777), Raman spectroscopy was applied to the real-time monitoring and pH prediction of CO₂ in bioreactor exhaust gas, which has clear industrial application value. By comparing the prediction effect of the traditional method with Raman exhaust gas spectroscopy, the high accuracy of the latter in CO₂ and pH monitoring is verified, which provides a new tool for the optimization of biopharmaceutical processes. Although the direct monitoring of CO₂ and pH in fermentation broths using Raman immersion probes was not effective, it provided a direction for subsequent technical improvements.Overall, this paper provides valuable experimental results for the application of Raman spectroscopy to bioprocess monitoring, but there is room for improvement in the details of the methodology and the depth of discussion.

 

1. The details of model construction need to be added, and the article mentions "internal model" and "random forest algorithm", but it lacks specific parameters and validation methods, and needs to be described in detail to ensure reproducibility.

 

2. The limitations of immersion probe experiments need to be analyzed in depth, and the lack of pre-trained models alone may not be comprehensive, and it is recommended to explore other potential interference factors, such as the complexity of fermentation broth composition and light scattering effects.

 

3. Some of the diagrams need to be as detailed as possible, and the schematic annotations of the device in Figure 1 need to be refined, such as marking the functions of key components and using arrows to clarify the direction of gas flow.

 

 

Author Response

Dear Reviewer,

Thank you very much for your detailed feedback. We have provided our responses to your comments in the attached PDF. We hope that the revisions we have made meet your expectations and adequately address your concerns.

Best regards

Tobias Wallocha & Michaela Poth

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study employed Raman off-gas spectroscopy to achieve time-resolved prediction of CO₂ concentration in fermentation exhaust. The results highlight the potential of Raman spectroscopy as a powerful tool for real-time bioprocess monitoring and control, demonstrating significant advantages in both accuracy and efficiency. Given the solid findings and overall quality of the manuscript, I would recommend it for publication in Fermentation after appropriate revisions.

• In Figure 2, could the authors clarify which specific peaks correspond to CO₂? Additionally, some peaks appear to arise from the baseline—could the authors comment on whether these are artifacts or potentially caused by other impurities in the off-gas?

• CO₂ is an acidic gas, yet in Figure 5, the pH measurements seem to focus on a more neutral range. Could the authors elaborate on whether the acidic nature of CO₂ might affect the accuracy of the pH prediction under different environmental conditions, particularly in more acidic settings?
  Could the authors clarify the rationale for maintaining CO₂ concentrations below 10% during the experiments? Is this threshold selected based on specific considerations for future applications or bioprocess constraints?

Author Response

Dear Reviewer,

Thank you very much for your detailed feedback. We have provided our responses to your comments in the attached PDF. We hope that the revisions we have made meet your expectations and adequately address your concerns.

Best regards

Tobias Wallocha & Michaela Poth

Author Response File: Author Response.pdf