Global Stabilizing Control of a Continuous Ethanol Fermentation Process Starting from Batch Mode Production

Round 1

Reviewer 1 Report

This study presents novel mathematical modeling and control strategies aimed at enhancing productivity in ethanol fermentation processes, focusing on global stabilizing control laws, adaptive control to prevent input saturation, and nonlinear estimation techniques validated through simulations (not through experimental data).

Upon review, it became apparent that the title and abstract may benefit from further specificity regarding the focus on mathematical modeling for the control of the ethanol fermentation process. Clarifying this aspect could greatly assist readers, particularly those with a keen interest in mathematical approaches within this field, in understanding the contribution of your study. Additionally, it could enhance the accessibility of your work within the scientific community. I respectfully suggest considering a slight adjustment to the title and/or abstract to accurately reflect the content of your research, thereby ensuring its full impact is effectively communicated to a broader audience.

There are two typefaces throughout the manuscript. I strongly recommend a careful reading of the manuscript to remedy these errors, as well as typographical errors (capital letters, unnecessary italics...).

The bibliography needs to be almost completely edited: in-text citations should not be superscripted; references do not follow the style of the journal, and there are some that are not properly referenced (e.g., citation 29). Please review this year's template. Also, given the large number of studies related to this topic, I believe that many more relevant studies could be referred in order to better highlight and contextualise the importance of this study (e.g., lines 45-46).

I appreciate the brief presentation of the rest of the sections at the end of the introduction, as it allows the reader to follow the work easily. There is no discussion whatsoever to help understand what the contribution of this study is, and I think it is absolutely necessary for it to be properly appreciated by the rest of the scientific community.

L119-120: Up to this point, no clear reference has been made to the fact that the model is to be carried out with a yeast (Saccharomyces) in mind. I think this should be stated more clearly in the introduction. Why does the word "bacteria" appear?

In the header of table 1 it should appear what the bold means, rather than in the text. In general, figures quality need to be improved as it is difficult to properly visualise them.

Author Response

Dear Reviewers and Editor,

Thank you very much for taking the time to review this manuscript. We appreciate the chance to revise the paper, and also thank the reviewers for their constructive remarks. Hereby we submit a revised version of our manuscript entitled “stabilizing control of a continuous ethanol fermentation process starting from batch mode production” (ID: Processes-2954447). Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Best regards,

Chi Zhai, Ph. D

Associate Professor

Faculty of Chemical Engineering

Kunming University of Science and Technology

Chemical Engineering Building, Room 314

727 Jing Ming South Road, Kunming, 650500

Tel: +86-137-0842-4757

E-mail: [email protected]

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors develop an analysis of ethanol fermentation strategies in order to evaluate the theoretical conditions to increase productivity. The focus is the control of the ethanol fermentation process.

The paper is interesting and well written.

I wish to highlight that it is not necessary to write T+273, but the author should use T for temperature measured in K and t for temperature measured in °C.

It could be better to use L for liter in order to avoid errors in reading the paper.

I think that some thermoeonomic considerations could be useful in discussion. See for example Grisolia's papers as reference, but also Sciubba's papers.

For the equations not formulated by the aithors it is useful a reference.

Line 209: \Dela S is better than \delta S

In Eq. (6) what happens if Y = 0?

Author Response

Dear Reviewers and Editor,

Thank you very much for taking the time to review this manuscript. We appreciate the chance to revise the paper, and also thank the reviewers for their constructive remarks. Hereby we submit a revised version of our manuscript entitled “stabilizing control of a continuous ethanol fermentation process starting from batch mode production” (ID: Processes-2954447). Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Best regards,

Chi Zhai, Ph. D

Associate Professor

Faculty of Chemical Engineering

Kunming University of Science and Technology

Chemical Engineering Building, Room 314

727 Jing Ming South Road, Kunming, 650500

Tel: +86-137-0842-4757

E-mail: [email protected]

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

I appreciate the effort you have put into addressing the concerns I raised. I am reassured that you have incorporated the importance of your work at the beginning of the summary. This adjustment will certainly help readers understand the importance of your research from the outset.

Regarding control strategies from batch production, thank you for providing me with additional context and justification for this approach. The comparison between batch and continuous fermentation that he offers in his response is particularly illuminating. He highlights the complexities and trade-offs inherent in each approach, underlining the importance of his focus on batch production and overall stabilising control. His explanation of the differences between traditional process control and the methodology employed in his work is insightful and would strengthen the manuscript, but I understand that you do not consider it necessary. 

Overall, I agree with the thoroughness of your response and the revisions made to the manuscript. I believe these changes will improve the clarity and impact of your work in this field.

P.S. Species names (Saccharomyces cerevisiae) should be in italics.