Exploiting Deep Eutectic Solvent-like Mixtures for Fractionation Biomass, and the Mechanism Removal of Lignin: A Review

Round 1

Reviewer 1 Report

I think this review is well written. The topic "Exploiting DES-like mixtures for fractionation biomass, mechanism removal of lignin" is described in sufficient detail.

This review may be very useful for those who are just starting to use DES-like mixtures.

However, two comments to the work are present.

1) The quality of Figure 2 should be improved.

2) Section 2 is very large and poorly digested. I recommend dividing it into 3-5 subsections, united by one idea.

Author Response

Dear Sir,

I would like to thank the reviewers for their recommendation to publish our paper and for their comments. We accepted all the comments and suggestions of the reviewers and modified the paper accordingly. The added parts are highlighted in blue. We hope you will find our paper after its revision acceptable for publication in your journal.

Looking forward to hearing from you soon,

Sincerely yours,

Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

A study conducted on “Exploiting DES-like mixtures for fractionation biomass, mechanism removal of lignin: A review ”  used di-17 ethyl ether to pretreat Plantain stem studied lignin recovery.  However, the logic of the writing was the biggest problem in this manuscript. Beside, there are several major points that need restructuring, restating and major language revision. 

· In Abstract: the authors stated that:  “The results of this review indicate that the physicochemical properties (acidity, hydrogen bond capacity, polarity, viscosity, and water content) of DES-like mixtures have a significant effect on the biomass fractionation process, and that these effects are mainly determined by the hydrogen bond donor (HBD). ” The statements are vague to understand.

· In section 1, Line 38-39 the authors stated that: “Those such as agricultural residues, forest residues, herbal and woody energy crops, and specialty crops are renewable and cheap with an annual production of 200 gigatons per year.” Again it is not clear. The scientific paper is a one of the ways of dissemination of findings, knowledge and technology transfer and its logic is important.

· In section 1, Line 41-42 the authors stated that: “The effective recovery of valuable content in lignocellulosic biomass requires techniques to effectively fractionate biomass to overcome the recalcitrant properties of the substances in this matrix. ” Sentence structure should be rewritten.

· In section 1, Line 55,  the authors stated that the physicochemical properties of specific biomass are strongly dependent on the concentration and nature of the main components. A table about the composition of different biomass components should be provided.

· In section 1, figure 2 should be improved.

· In section 1, Line 138-143, the logical expression needs to be modified.

· In section 1, For a review article, there lacks a literature review on the current research status of DES-like mixtures for fractionation biomass, it is very improtent for a review article.

· In section 2, the mechanism review section should be supplemented with more graphs, tables, and reaction formulas.

· In section 3, perspective should be given.

· Conclusions should be refined, it is too long and vague to understand.

This manuscript need intensive revision for writing. the speaking language were seen thoughout the manuscript.

Author Response

Dear Sir,

I would like to thank the reviewers for their recommendation to publish our paper and for their comments. We accepted all the comments and suggestions of the reviewers and modified the paper accordingly. The added parts are highlighted in blue. We hope you will find our paper after its revision acceptable for publication in your journal.

Looking forward to hearing from you soon,

Sincerely yours,

Authors

Author Response File: Author Response.pdf

Reviewer 3 Report

The review “Exploiting DES-like mixtures for fractionation biomass, mechanism removal of lignin: A review” is devoted to the current topic of preparing lignocellulosic biomass for further use. DES-like mixtures are listed in detail in the manuscript and scientifically presented as green lignin solvents from various types of lignocellulosic feedstocks. The review covers a sufficient number - 64 publications, among which the majority are from 2020-2023, which should be attributed to the positive aspects of the article. It is a pity that the authors did not find a reason to cite their own review, which was published a year earlier: https://doi.org/10.3390/en15249333. The authors have a good knowledge of the physicochemical properties of DES-like mixtures and clearly describe the mechanism of the process of interaction between the solvent and lignin, giving well-founded arguments and specific examples of application. According to the main criteria (relevance, target setting, objects of research, terminology, main conclusions), the manuscript corresponds to the Sustainability publication. But there is a small list of comments to the review.

Notes:

1. Abstract, line 10-11: the expression “fractionation of lignocellulosic materials” is incorrect, because the fractionation process is directed not at the material, but at the raw material. To correct.

2. Introduction, lines 56-57: the sentence “The lignocellulosic biomass is highly resistant to fractionation by the heterogeneous matrix formed between hemicelluloses and lignin, which are cross-linked through strong covalent and hydrogen bonds.” is incorrect because the main polymer cellulose is excluded , which is also associated with two other polymers hemicellulose and lignin. To correct.

3. Introduction, line 81, it is recommended to put the expression “low production costs” in a separate sentence, provide numbers and provide links.

4. Introduction, lines 136-138, sentence “Recent studies have highlighted the potential of DES-like mixtures for biomass pretreatment, substance extraction, cellulose modification, and the creation of nanocellulose fibers, nanocrystals, and microcrystalline nanocellulose.” either expand into a separate paragraph with specific explanations of how the use can provide effective chemical modification or produce “nanocellulose fibers,” or provide links to such examples directly in the sentence.

Please note that you have two typos in the expression “nanocrystals, and microcrystalline nanocellulose”: there are “nanocrystalline cellulose” and “microcrystalline cellulose”. To correct.

5. Figure 2. Directly in the figure, after “pre-treatment” you need to put “fibers” in the first place, then use another arrow to highlight additional stages up to “bioethanol”.

6. Section 2 is either divided in half and given titles, or subheadings are given within section 2. The review cannot consist of two sections, one of which is an introduction.

7. It is logical to quote https://doi.org/10.3390/su152115343

8. Line 528. Discussion of "lactic acid" as a solvent. It must be justified or explicitly stated that the use of lactic acid as a fractionation solvent is not considered if the purpose of the fractionation is to obtain a substrate for the production of the lactic acid fermentation product.

9. Lines 706-707. Check out the sentence “The work by Ma et al. [55] focused on the degumming of hemp fibers using DES-like mixtures based on choline chloride and urea with the participation of alkaline pretreatment (H2O2)." The formula H2O2 refers to which substance? Look into this issue and fix it.

10. Section 3. Summary and conclusions. After reading carefully, I discovered that there is no erroneous statement that the use of DES-like mixtures can contribute to the process of obtaining “nanocrystalline cellulose” and “microcrystalline cellulose”. Therefore, this statement needs to be corrected (see remark 4).

Author Response

Dear Sir,

I would like to thank the reviewers for their recommendation to publish our paper and for their comments. We accepted all the comments and suggestions of the reviewers and modified the paper accordingly. The added parts are highlighted in blue. We hope you will find our paper after its revision acceptable for publication in your journal.

Looking forward to hearing from you soon,

Sincerely yours,

Authors

Author Response File: Author Response.pdf

Reviewer 4 Report

The manuscript is a review that is easy to follow and leads the reader to understand the importance of DES-like mixtures, especially in the pretreatment of biomass and lignin removal.

My suggestions are:

1) The title. I believe it would be better to write the complete name Deep Eutectic Solvents-Like Mixtures (DES-like mixtures).

2) Improving the tables. They need to keep the journal format.

3) About Figure 2. It needs to be larger in size and in higher resolution.

Author Response

Dear Sir,

I would like to thank the reviewers for their recommendation to publish our paper and for their comments. We accepted all the comments and suggestions of the reviewers and modified the paper accordingly. The added parts are highlighted in blue. We hope you will find our paper after its revision acceptable for publication in your journal.

Looking forward to hearing from you soon,

Sincerely yours,

Authors

Author Response File: Author Response.pdf

Reviewer 5 Report

This review concerns DES-like mixtures for biomass fractionation, a curent topic. A special focus on lignin removal is pproposed.

The first part of the paper reds rather well (until page 6) but the second part is a listing of the different works reported in the literature, more difficult to follow This part must be modified to bring out the originality of the different approaches and could be reduced. The Figure 2 is poor quality and could be separate in two or three indépendant Figure coming with the appropriate text.

With some modifications this paper could be very useful for reader of Sustainability to know more about DES-like mixtures.

Author Response

Dear Sir,

I would like to thank the reviewers for their recommendation to publish our paper and for their comments. We accepted all the comments and suggestions of the reviewers and modified the paper accordingly. The added parts are highlighted in blue. We hope you will find our paper after its revision acceptable for publication in your journal.

Looking forward to hearing from you soon,

Sincerely yours,

Authors

Author Response File: Author Response.pdf

Round 2

Reviewer 5 Report

Authors followed the reviewer's recommendations to improve their paper and improve the reading.