Sustainable Production of Lactic Acid Using a Perennial Ryegrass as Feedstock—A Comparative Study of Fermentation at the Bench- and Reactor-Scale, and Ensiling

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article is devoted to the actual problem of obtaining lactic acid using the perennial herb Lolium perenne. Despite the relevance and the large volume of research conducted, there are some comments on the article: 1. Check the numbering of the tables, some tables have one number. 2. It is necessary to add more information about Lolium perenne. The article states: "Among the others, perennial ryegrasses (Lolium perenne) are considered an important resource..." (line 41-42) - in what area is it a resource? 3. The last paragraph "Introduction": I ask the authors to make sure that this paragraph does not refer to the item "Materials and methods". 4. In the introduction, it is necessary to justify why Lolium perenne was chosen. 5. What other crops are used for the production of lactic acid and why was the variety Lolium perenne chosen? 6. In paragraph 2.1, it is necessary to add information about the physico-chemical properties of Lolium perenne. Which component is there a lot in this raw material, as a result of which it was chosen to produce lactic acid. Why is it chosen to produce lactic acid? 7. According to the requirements of the journal, the item "Results and discussion" should be divided into 2 items: "Results" and "Discussion". 8. Why tables 3 and 4 show the results of juice analysis of only three (Honroso and Explosion are not represented) and two varieties (Arvicola, Agaska and Barmigo are not represented), and not all 5 (Arvicola, Agaska Barmigo, Honroso and Explosion), as indicated in Table 1 (page 5) and 2 (p. 9)? After eliminating the comments, the article can be accepted for publication in the journal Sustainability.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The present manuscript is based on an excellent idea, which is properly executed.

 

However, it requires addressing a few questions. 

 

Lines 31-37. How are these facts related to the present study?

 

Lines 38-40. Mention some of the most important products. 

 

Table 1 is labeled on two tables; please check the numbering.

 

Figure 3. What does the pink background indicate? 

 

Data presented in tables requires SD and statistical symbols to know the significance level. 

 

Data presented in all figures requires statistical symbols to know the level of significance. 

 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The experimental article with the long title "Sustainable production of lactic acid using Lolium perenne as feedstock- A comparative study of fermentation at bench- and reactor-scale, and ensiling" is devoted to obtaining lactic acid from the plant raw material Lolium perenne. The authors discuss the media they used and compare bench- and reactor scale. The relevance of the topic is justified by the general attention to the platform chemical, in this case, lactic acid. The authors excellently discuss the idea of obtaining lactic acid from lignocellulose, provide a table with examples of lactic acid production and put forward the goal of obtaining lactic acid from plant juice. This approach differs greatly from the main idea of obtaining lactic acid by a longer route, including preliminary treatment of lignocellulose, enzymatic hydrolysis of the substrate and subsequent fermentation. The author's approach excludes the possibility of using dry lignocellulose. Therefore, the main remark to this manuscript: discuss examples of obtaining lactic acid from plant juices right in the introduction and show the advantages of the author's approach. Below is a list of recommendations for improving the article:

1. It is recommended to correct the title of the manuscript, formulate a scientific hypothesis. Perhaps this will lead to a reduction in the text and the list of cited literature.

2. Lines 125-128. These statements concern solid lignocellulose, not plant juice. It is recommended to correct this text, since such statements can misinform a young reader.

3. Lines 151, 327, 366, etc. It is recommended to correct the numbering of tables.

4. It is recommended to provide data on the yield of juice during squeezing.

5. Lines 551-556. It is recommended to correct this text, since it is incorrect to emphasize the advantage of obtaining lactic acid from squeezed plant juice with the fermentation process from the hydrolysate of pre-treated lignocellulose. Obviously, the second process [62, 63] is much more complex and attractive due to its versatility. 6. Section 3.6 of the article is very important and in favor of the scientific integrity of the authors. It is recommended to include an additional sentence in the abstract about the lactic acid output from fresh grass in the same units of measurement as from juice, in order to correctly orient the reader. This statement should also be present in the Conclusion.

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

The article “Sustainable production of lactic acid using Lolium perenne as feedstock- A comparative study of fermentation at bench- and reactor-scale, and ensiling” is devoted to the study of the possibility of using Perennial ryegrass juice as a component of the nutrient medium for bacterial production of lactic acid.

A large number of research methods were used in the experimental work. However, many corrections are needed in the article. Many English words do not fit the meaning of the text. The translation needs to be checked.

The article can be published in the journal “ Sustainability ” after major revisions have been made.

Line 21. Lactic acid production was 26.61 ± 1.2 g / L in press-juice medium. The value for the complex medium of 22 g / L is given without error.

Table 1. The abbreviation SSF needs to be expanded.

The expansion of “LAB” should be done before Table 1, not after it.

23 feedstock sources are given in table 1 for LA production. Discussion of the table is not given.

The authors chose Lolium perenne as feedstock. It is necessary to indicate the identity of the names Lolium perenne = perennial ryegrass at the beginning of the article. The authors indicated this only in the Abstract. Why did the authors choose this particular plant? At what period of plant development were the samples collected?

There are two first tables in the article.

For each device used, the name of the device, the manufacturer, the year and country of manufacture must be given.

Table 1. “Lolium perenne varieties used in this study with information on ploidy and breeder”. Information on the breeder must be given in more detail.

Line 152. In what interval were the IR spectra recorded?

Line 177. Which ions were determined?

What pH meter was used to check the pH readings during the study?

Line 199. What does v/v mean? Volume per volume?

Line 221. Why were these time intervals chosen?

Equation 8 does not contain the QCELL value. Please correct the typo.

Table 2. I would like to clarify the units of measurement (dt/ha) for DM.

Table 3. Values ​​should be rounded equally (e.g. to the first decimal place)

Line 371. If several experiments with the same plant species at different periods of vegetation are to be conducted, then such important conclusions can be drawn. The comparison of experiments with different plant varieties is given in the article. Since the plants were collected at different times, such conclusions cannot be drawn.

Line 528. There may be an empty line.

Line 597 What was the yield LA of Agaska.

Line 631. The error is not given.

Line 759, 839. The reference may be incorrectly formatted.

Grasses can absorb various harmful substances from contaminated soil. Was the obtained lactic acid analyzed for chemical purity?

Author Response

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Author Response File: Author Response.docx

Reviewer 5 Report

Comments and Suggestions for Authors

Please check the enclosed file

Comments for author File: Comments.pdf

Comments on the Quality of English Language

I suggest language improvements, a professional editing would improve the overall quality

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors thoroughly addressed the suggestions and questions raised by the reviewer, and this manuscript could be accepted after revising minor errors. 

 

Regarding the manuscript's title, using "a perennial ryegrass" makes it a little ominous, such as "Which ryegrass?" It is better to specify the name, as it was in the first draft. 

 

The reviewer suggests the title, "Sustainable production of lactic acid using Lolium perenne, a perennial ryegrass, as feedstock- A comparative study of fermentation at bench- and reactor-scale, and ensiling." 

 

Double spaces are used at several places in the whole manuscript, which need revision. 

Comments on the Quality of English Language

Minor language and grammar revision is required. 

Author Response

Comments 1: Regarding the manuscript's title, using "a perennial ryegrass" makes it a little ominous, such as "Which ryegrass?" It is better to specify the name, as it was in the first draft. 

The reviewer suggests the title, "Sustainable production of lactic acid using Lolium perenne, a perennial ryegrass, as feedstock- A comparative study of fermentation at bench- and reactor-scale, and ensiling." 

Response 1: The authors appreciate the feedback. However, the title was changed according to a comment from another reviewer. The authors prefer to be more general with the title. 

Comments 2: Double spaces are used at several places in the whole manuscript, which need revision. 

Response 2: The authors thank for the feedback and they revised deeply the manuscript. 

Reviewer 4 Report

Comments and Suggestions for Authors

I thank the authors of the article and the editor of the journal for the work done. The article has become much better. The article can be published after minor corrections.

Line 75. Text not related to the article.

The year of manufacture must be given for all devices.

Author Response

Comments 1: Line 75. Text not related to the article.

Response 1: The authors appreciated the input. Lines 74-75 justified why we used a homolactic bacteria for our experiments.

 

Comments 2: The year of manufacture must be given for all devices.

Response 2: The authors did not have the year of each device, so they did not give them.  

Reviewer 5 Report

Comments and Suggestions for Authors

Many thanks for your additional work

Author Response

Comments 1: Many thanks for your additional work

Response 1: Thank you for helping in the manuscript's improvement.