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Article
Peer-Review Record

Evaluation and Characterization of Alginate Extracted from Brown Seaweed Collected in the Red Sea

Appl. Sci. 2021, 11(14), 6290; https://doi.org/10.3390/app11146290
by Sarah H. Rashedy 1,*, Mohamed S. M. Abd El Hafez 1,2, Mahmoud A. Dar 1, João Cotas 3 and Leonel Pereira 3
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Appl. Sci. 2021, 11(14), 6290; https://doi.org/10.3390/app11146290
Submission received: 24 June 2021 / Revised: 4 July 2021 / Accepted: 5 July 2021 / Published: 7 July 2021
(This article belongs to the Special Issue Algae as a Nutritional and Bioactive Biomass)

Round 1

Reviewer 1 Report

The paper entitled ‘Evaluation and characterization of alginate extracted from  brown seaweed collected in the Red Sea’ prepared by Rashedy et al. presents important comparison of five species of dominant brown seaweeds in terms of their alginate yield and properties.  The paper is well prepared. The presented studies results are interesting, presented in form of figures and tables. Statistical analysis confirms reliability of the results. On the whole, the paper is suitable for publication in Applied Sciences nevertheless the following points should be improved/corrected:

  1. Table 4: please provide explanation (i.e. below table) the symbols: FG, FGG, etc. It will be more readable.
  2. Table 4. Please provide statistic information (standard deviation) in the table
  3. English correction is recommended

Author Response

REVIEWER 1:

Comment 1: The paper entitled ‘Evaluation and characterization of alginate extracted from  brown seaweed collected in the Red Sea’ prepared by Rashedy et al. presents important comparison of five species of dominant brown seaweeds in terms of their alginate yield and properties.  The paper is well prepared. The presented studies results are interesting, presented in form of figures and tables. Statistical analysis confirms reliability of the results. On the whole, the paper is suitable for publication in Applied Sciences nevertheless the following points should be improved/corrected:

  1. Table 4: please provide explanation (i.e. below table) the symbols: FG, FGG, etc. It will be more readable.
  2. Table 4. Please provide statistic information (standard deviation) in the table
  3. English correction is recommended

 

Answer 1: Firstly, we would like to thank the reviewer for his/her words. They were very valuable in improving the overall quality of the manuscript. All the question were addressed, at blue color. Due to be analysis of the NMR spectra, we did not have standard deviation values because all the samples spectra were identical without differentiation. The English was revised.

Reviewer 2 Report

See the attached file

Comments for author File: Comments.pdf

Author Response

Reviewer 2:

 

Comment 1: Major observations

It seems that Figure 6 duplicate Table 5. Anyway, chemical composition should be always presented in table 4. I recommend authors to verify if the information is not duplicated and to remove Figure 6.

Line 347. Table 5 do not contain the discussed information about alginate yield. I recommend authors to verify the given information. It should be Figure 3.

Minor observations

Line 109. Add the past tense: “…created and managed by Guiry and Guiry”.

Line 295 : Add the plural :” The results...”

Line 389. I suggest to use the following form : “… is good by according to the FAO report

Answer 1: Firstly, we would like to thank the reviewer for his/her words. They were very valuable in improving the overall quality of the manuscript. We addressed the all questions in orange.

Figure 6 was deleted. Table 4 is only related to the NMR spectra analysis, and table 5 is related to other techniques to detect the composition by biochemical analysis, unlike the NMR and FTIR which are spectroscopic methods. The table 5 is related to the alginate characterization of alginate obtained and not alginate yield, thus the alginate characterization by the alginate physical properties and alginate spectroscopy analysis were considered more important after the alginate yield to confirm the rheological properties and alginate characterization. Where phytochemical (without results of other seaweed compound with exception of saponins, which is explained in the section 3.5) and biochemical analysis were done to confirm the results of FTIR and NMR by biochemical analysis (plus, to quantify the alginate impurities which is the main topic in the table 5, and alginate yield (carbohydrates)), to have a robust and coherent analysis of the alginate obtained. Although we added information about the topic in in results section 3.6.

Reviewer 3 Report

The paper "Evaluation and characterization of alginate extracted from brown seaweed collected in the Red Sea", written by Rashedy, S et al. is of interest to researchers in the field of biopolymers. The paper is well documented and argued.
I did not find mentioned how long after the algae storage the determinations were made. It would also be interesting if the authors would resume these determinations at different storage periods, in order to observe possible changes in the algae characteristics.

 

Author Response

Reviewer 3:

Comment 1: The paper "Evaluation and characterization of alginate extracted from brown seaweed collected in the Red Sea", written by Rashedy et al. is of interest to researchers in the field of biopolymers. The paper is well documented and argued.
I did not find mentioned how long after the algae storage the determinations were made. It would also be interesting if the authors would resume these determinations at different storage periods, in order to observe possible changes in the algae characteristics.

 

Answer 1: Firstly, we would like to thank the reviewer for his/her words. They were very valuable in improving the overall quality of the manuscript. We addressed all questions in purple. We added information about the storage time (which happened after seaweed drying), line 116/117, section 2.2 last sentence. We concord with reviewer, it is planned to do that in the future, added in the conclusion.

 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.


Round 1

Reviewer 1 Report

I don't have more questions

Author Response

Reviewer 1:

Comment 1: I don't have more questions

Answer 1: Firstly, we would like to thank the reviewer for his/her words.

Reviewer 2 Report

Line 61. Should read ‘easy to incorporate into food, well accepted for human food consumption, and quick to adapt for a specific role.’

The tests for phlorotannins and terpenoids seem very basic and don’t seem to have reference controls. For example FC assay for phenolics would give a better indication of the level of phenolic present. For these tests are authors following known procedures? They are not referenced if so.

Figure 5. I’m unsure if these are due to the anomeric protons of mannuronic acid (A) because you would expect the anomeric proton to be a doublet. (B) residual H2O in D2O will show as a broad peak at 4.7-4.8 which is very close to this peak and I would expect some water in this type of sample. I would like to see the rest of the spectra to see if this is actually showing much in terms of sugars as from this peak I am unconvinced.

Tannins are very commonly covalently bonded to alginate – this is a very common issue for food as it can affect the taste. I would suggest performing a better colorimetric assay for phlorotannin content.

Author Response

Comment 1: Line 61. Should read ‘easy to incorporate into food, well accepted for human food consumption, and quick to adapt for a specific role.’

Answer 1: The question was addressed in the manuscript.

 

Comment 2: The tests for phlorotannins and terpenoids seem very basic and don’t seem to have reference controls. For example, FC assay for phenolics would give a better indication of the level of phenolic present. For these tests are authors following known procedures? They are not referenced if so.

Answer 2: The colorimetric analysis for phytochemical analysis was done due to be rapid assay and it is very specific, and it was cited in the methodology the reference where we gathered the rapid assay methodology (section 4.6, all the section was based in the methodology of Trease and Evans and Sofowora). If these methods resulted in that alginate positive with phenols, tannins, and terpenoid, in this case, colorimetric methods are required for knowing their concentrations by using standards. FC assay can give false analysis due to be easily influenced to other seaweed compounds, mainly sulphated polymers (10.1007/s10811-020-02362-3, 10.1016/j.recqb.2017.04.003). Also, if their other seaweed compounds the NMR and FTIR demonstrated also that. Because of that, we added specific assays in the yield of ashes, lipids and proteins.

 

 

Comment 3: Figure 5. I’m unsure if these are due to the anomeric protons of mannuronic acid (A) because you would expect the anomeric proton to be a doublet. (B) residual H2O in D2O will show as a broad peak at 4.7-4.8 which is very close to this peak and I would expect some water in this type of sample. I would like to see the rest of the spectra to see if this is actually showing much in terms of sugars as from this peak, I am unconvinced.

 Answer 3: The samples of alginate for NMR are the same samples of FTIR and all samples are completely dry (using, the moisture content in samples are present in Table 2 in manuscript). Although the humidity, the crossing the data obtained in the FTIR and NMR are positively correlated. The FTIR do not show high content in humidity (3200 cm-1 area)

The original the images, before the analysis: see PDF in annex, please

Comment 4:  Tannins are very commonly covalently bonded to alginate – this is a very common issue for food as it can affect the taste. I would suggest performing a better colorimetric assay for phlorotannin content.

Answer 4: This was analyzed using the FTIR analysis, which can detect the phlorotannins in seaweed, as demonstrated in a previous of the authors (10.1007/s00343-019-8111-3), thus giving more specific characterization. We added a sentence in discussion about the topic. And the steps of his extraction, with the HCl pre-treatment, the organosoluble compounds are hydrolysated and only the alginate and polymer are maintaining intact after the pre-treatment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper entitled 'Evaluation and characterization of alginate extracted from 2 brown seaweed collected in the Red Sea' is aimed to extraction of alginate and determination phytochemical profile and phytochemical properties of the obtained samples. Auhors decided to use five species of dominant brown seaweeds. The paper include sufficient Introduction, methodology, results and discussion. References are to date and adequate. On the whle the presented studies are interesting. In accordance with my knowledge, there are available similar studies based on  brown seaweeds but the papers are based on different methods. The paper is suitable for publication but some points should be imrpoved:

  1. Abstract is too long. In accordance with authors’ guideline, this part should be a total of about 200 words maximum.
  2. Why there are a lot of words in red? In whole manuscript.
  3. Table 1 is not suitable. Please improve format of this part.

Author Response

Reviewer 3 (at green)

Comment 1: The paper entitled 'Evaluation and characterization of alginate extracted from 2 brown seaweed collected in the Red Sea' is aimed to extraction of alginate and determination phytochemical profile and phytochemical properties of the obtained samples. Auhors decided to use five species of dominant brown seaweeds. The paper includes sufficient Introduction, methodology, results and discussion. References are to date and adequate. On the whole the presented studies are interesting. In accordance with my knowledge, there are available similar studies based on brown seaweeds, but the papers are based on different methods. The paper is suitable for publication but some points should be improved:

Answer 1: Firstly, we would like to thank the reviewer for his/her words. They were very valuable in improving the overall quality of the manuscript. We corrected the name of the compound.

Comment 2: Abstract is too long. In accordance with authors’ guideline, this part should be a total of about 200 words maximum.

Answer 2: We addressed the problem.

Comment 3: Why there are a lot of words in red? In whole manuscript.

Answer 3: This was resubmission, and the editor ask to highlight the changes.

Comment 4: Table 1 is not suitable. Please improve format of this part.

Answer 4: This table was redone and formatted according to the journal guidelines

Round 2

Reviewer 2 Report

The NMR experiments need to be completely removed or redone - or show the full NMR spectrum. Authors have not changed any suggestions made. I believe the peak they are referring to in figure 5 is just H2O in D2O. The assays used are not referenced. 

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