Effects of Temperature Shifts on Microbial Communities and Biogas Production: An In-Depth Comparison

Round 1

Reviewer 1 Report

 

The article "Discover the Effects of Temperature Shifts on Microbial Communities and Biogas Production: An In-Depth Comparison" by Sudiartha et al. is interesting in that it deals with a subject that has received little attention in the literature. While mesophilic and thermophilic anaerobic digestion are well documented, the transition states between temperatures are much less so. However, the current version of the article needs to be improved before it can be published.

First of all, the reactor management method is not clear. The authors talk about fed-batch, but in the materials and methods section there is only mention of 2 injections of 2 mL of glucose solution, one at start-up and the other after 1 month. Is this really what was used? The gas fluctuations in Figure 2 seem to indicate a cycle of 5 days of feeding followed by 2 days without feeding.

Next, the choice of a 100 g/L glucose solution seems strange, firstly because in doing so the authors neglected a large part of the microbial communities, and secondly because under these conditions there is a significant risk of volatile fatty acid production, which the authors do not seem to have measured, which is regrettable. Yields and microbial populations were potentially affected.

The volume of the reactors is also surprising. Why were such small volumes used (70 mL plus the multiple additions of glucose solution), which makes taking samples for analysis tricky? Furthermore, when were the samples taken for genomic analysis, on what date, and what volume was taken? None of this is described in the text.

Finally, the title is a bit bombastic. A simpler title such as "Effects of Temperature Shifts on Microbial Communities and Biogas Production" would be more appropriate.

Finally, are the gas volumes and the resulting figures standardised and expressed under standard conditions (0°C, 100 kPa)?

Author Response

Dear reviewers, we would like to thank you for the noteworthy feedback. We appreciate the time and effort that you have dedicated to providing valuable feedback on my manuscript. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewer. We have highlighted the changes in the manuscript using the Track Changes function.

Here is a point-by-point response to the reviewer’s comments and concerns. The letters written in red ink are the concerns, comments, and questions. While the letters written on black ink are the responses from us as the authors.

Author Response File: Author Response.pdf

Reviewer 2 Report

The present study designed two scenarios to illustrate the effect of temperature on biogas production. Besides, sequencing analysis was used to reveal the dominated microbes on biogas production with the changed temperature.

The experimental design of this paper is reasonable, and it has certain innovative and guiding value. The writing, drawings and the tables are very standard. Have a full discussion of the results of their experiments.

Based on the above considerations, my recommendation is accept in present form

Author Response

We thank the reviewer for the positive feeback on our manuscript. We are delighted to hear that the reviewer found our experimental design reasonable and appreciated its innovative and guiding value. We would also like to express our sincere gratitude for recommending the acceptance of our paper in its present form.

Response to Reviewer 2 Comments

 

Dear reviewers, we would like to thank you for the noteworthy feedback. We appreciate the time and effort that you have dedicated to providing valuable feedback on my manuscript. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewer. We have highlighted the changes in the manuscript using the Track Changes function.

 

Here is a point-by-point response to the reviewer’s comments and concerns. The letters written in red ink are the concerns, comments, and questions. While the letters written on black ink are the responses from us as the authors.

 

• Point 1: The present study designed two scenarios to illustrate the effect of temperature on biogas production. Besides, sequencing analysis was used to reveal the dominated microbes on biogas production with the changed temperature. The experimental design of this paper is reasonable, and it has certain innovative and guiding value. The writing, drawings and the tables are very standard. Have a full discussion of the results of their experiments.Based on the above considerations, my recommendation is accept in present form.

 

Response :  We thank the reviewer for the positive feeback on our manuscript. We are delighted to hear that the reviewer found our experimental design reasonable and appreciated its innovative and guiding value. We would also like to express our sincere gratitude for recommending the acceptance of our paper in its present form.

Reviewer 3 Report

 

 

Line 23: „decrease of_83%,“ replace with „decrease of 83%,“

 

Line 41: „and other elements,“ replace with „and other compounds,“

 

Line 45: „involvement of various physiological microorganisms involved in hydrolysis,“ replace with „involvement of physiologicaly various microorganisms involved in hydrolysis,“

 

Line 46-47: „In order to generate methane: acetate, H2, and CO2 are the primary components, “

Colon symbol can be replaced by comma.

 

Line 50: „Methanosaetaceae spp.. „ Delete the redundant full stop symbol.

 

Line 110: „The properties of the inoculum (I) are presented in Table 1.“
Please explain what is „inoculum (I)“? Is it the Roman numeral one or the letter I?

 

Line 114-115: „following essential nutrients required for bacterial growth“
Please cite the literature from which this composition was taken.
Was it added as a stock solution? What is the concentration of the stock solution and what volume was added?

 

Line 120: Serum vials were used to produce methane. Please correct the word reactor, which is used in several places in the text and on the graphs.

 

Line 128: „self-fermentation“ – please, explain

 

Line 137, table 2: Please clarify the experiment plan in the text (conditions and labels, meaning of U42 -U48, D55-D48). . How many parallel serum vials were there for each experiment and how were they labeled?

 

Line 162 – “reactor” – it is not reactor

 

Line 487: „due to the intense food competition“ – please write  „nutrient” instead of “food”

 

Experimental Setup section (2.2.) should be rewritten and clarified

 

Minor editing of English language required.

Author Response

Dear reviewer, we would like to thank you for the noteworthy feedback. We appreciate the time and effort that you have dedicated to providing valuable feedback on my manuscript. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewer. We have highlighted the changes in the manuscript using the Track Changes function.

Here is a point-by-point response to the reviewer’s comments and concerns. The letters written in red ink are the concerns, comments, and questions. While the letters written on black ink are the responses from us as the authors.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

 

I would firstly like to thank the authors for the efforts they have made to improve the text and its comprehensibility. However, it would be desirable to further improve the text before publication.

 

Section 2 has been modified, but it is still not clear: how much glucose solution was added, on which days, and what was the cumulative volume over time?

 

Regarding the volume of vials, even if the answer is based on existing literature, the vast majority of researchers in the field use larger, more representative volumes, which, for example, would have made it possible to measure VFA's. For example, BMP tests use volumes of 400 to 500 mL. The reviewer can only encourage changes in experimental conditions for future work.

 

With regard to the title, the term "discovery" implies that the authors were the very first to work on temperature variations in anaerobic digestion. The term "Discover" should be removed from the title.

Author Response

Dear reviewers, we would like to thank you for the noteworthy feedback. We appreciate the time and effort that you have dedicated to providing valuable feedback on my manuscript. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewer. We have highlighted the changes in the manuscript using the Track Changes function according to Editor’s suggestion.

Author Response File: Author Response.pdf

Reviewer 3 Report

         Point 9: Line 128: „self-fermentation“
Please provide references in the manuscript that mention establishing a sustainable anaerobic condition inside the vials and self-fermentation.

 

·         Table 2.
Please, note in the manuscript how many vials there were for each condition sets. Was there only one vial for each condition?

 

Line 155 „Kpa“ - please replace with kPa for kilopascal

 

Author Response

Dear reviewer, we would like to thank you for the noteworthy feedback. We appreciate the time and effort that you have dedicated to providing valuable feedback on my manuscript. We have been able to incorporate changes to reflect most of the suggestions provided by the reviewer. We have highlighted the changes in the manuscript using the Track Changes function.

Author Response File: Author Response.pdf