Insights into the Effects of CeO₂ Nanoparticles on Medium-Chain Carboxylates Production from Waste Activated Sludge

Round 1

Reviewer 1 Report

The introduction must be definitely improved and the meaning of the work should be better motivated.

After processing the sludge at 120 C, we have an excellent material for hydrogen production - there are several papers showing this. The advantage is the spontaneous separation of the product from the bioreactor.

The authors have completely failed to show the sense of implementing their technology. After all, in addition to the product, we get a complex post-reaction mixture - the costs of separation and purification will be horrendous and exclude the sense of such production.

 

The authors focused only on biological interactions, although they consider changes in the technological process.

Already in this issue I have doubts - the harmful effects of nanoparticles have been noticed and described for a long time, so why the idea of ​​showing the harmful effects of such a huge dose as 100 mg / g.

Even if we do continuous fermentation, we still need to partially allow the wort. So - we discharge nanoparticles into the environment, which is harmful.
The authors, having biological results, could discuss the harmfulness of nanoparticles more, instead of considering the synthesis of compounds.

 

Author Response

 Thanks for giving us the opportunity to revise the manuscript. We have carefully revised the manuscript based on the comments. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have written an article entitled “Insights into the effects of CeO₂ nanoparticles on medium-chain carboxylates production from waste activated sludge”. The manuscript is quite interesting, well framed, and based on the preparation of medium chain carboxylates (MCCs) from waste activated sludge (WAS), in this approach the CeO₂ NPs improved the solubilization of WAS, resulting in higher production of MCCs. Furthermore, the results exhibited that MCCs-microbe Clostridium sensu stricto were enriched in the control group, while the relative abundance of this genus was significantly reduced with 100 mg/g-TS CeO₂ NPs. The article has some grammatical and sentence errors, and the language organization needs to be improved. The authors have described the concept to an adequate extent but the manuscript still needs some Minor corrections before publishing in the Sustainability.

I advise the authors to consider the following points when revising their manuscript.

Comment 1: Minor punctuation revision is required in the manuscript.

Comment 2: The manuscript needs to be checked for typographical/ grammatical, superscript, and subscript errors. For. e.g: Line 25, “CeO2 NPs” should be “CeO₂ NPs”

Comment 3: The introduction is well-written, and appropriate information is provided. However, include some more recent year’s literature in the introduction section to strengthen the section. It can improve the visualization of the paper’s materials for the readers in the different areas of study.

Comment 4: Include the structured graphical abstract.

Comment 5: All Figure's resolution is very poor, so improve the resolution of the images.

Comment 6: Provide some supplementary data of the procured CeO₂ NPs.

Comment 7:  Check the reference style and maintain the journal names as abbreviations according to the MDPI format. Also, correct the superscript and Subscript errors in the references.

Author Response

 Thanks for giving us the opportunity to revise the manuscript. We have carefully revised the manuscript based on the comments. 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Not only the reviewer but also the readers should be informed. Hence, information about the economic potential should be added to the introduction.

If something is in mg/L, I don't understand how it can be profitable in large-scale industrial production.

Not all symbols are clear, like mM C - mini mole of carbon?

Figure 1 - production should be related to the substrate unit, eg kg C/kg C of substrate
and so we have data on the basis of x1 less and for X2 more - this is not scientific

In addition, productivity should also be given, eg kg C/m3 day

I do not find basic technological data in this work - so how am I supposed to assess the sense of such activities.

If this is to be a work about biology and for biologists, the title is inadequate.

Summing up, the text still requires a lot of additions and explanations.

 

I don't understand the drawing very well
Consumption of ethanol
The reaction is powered by ethanol?
Then what does it mean when we use a 1:2-1:4 ratio?

 

Author Response

  Thank you for the valuable comments to improve the quality of the manuscript.   

Author Response File: Author Response.docx

Round 3

Reviewer 1 Report

It would be advisable to introduce more descriptions into the text in relation to the previous review

Author Response

Thank you for your valuable comments to improve the quality of the manuscript. 

Author Response File: Author Response.docx