Harnessing Microalgae and Cyanobacteria for Sustainable Agriculture: Mechanistic Insights and Applications as Biostimulants, Biofertilizers and Biocontrol Agents

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments Flores et al – Agriculture

The manuscript by Flores et al., “Microalgae and cyanobacteria and their application in agriculture: natural-based biofertilizers, biostimulants and biocontrol compounds”, provides a comprehensive review of the current knowledge on the potential and applications of microalgae and cyanobacteria in sustainable agriculture. It is well structured and written, summarising the key traits of these microorganisms in relation to plant growth promotion and soil fertility improvement. The work also compiles information on commercially available products derived from these microorganisms and highlights the knowledge gaps and challenges that need to be addressed to enhance their agricultural use. However, some points could be further refined to enhance the overall quality of the work.

Major points:

• The manuscript would benefit from a clear definition of “biofertilizer” and a concise explanation of how it differs from “biostimulants” from the authors’ perspective.
• Standardise the definition of “microalga,” as in some sections both microalgae and cyanobacteria are mentioned, whereas in others the term “microalgae” is used alone to encompass both eukaryotic microalgae and cyanobacteria.
• These two aspects should be clarified early on throughout the introduction.
• Sections 2 and 3 exhibit some inconsistencies in the application of the terms “biostimulant” and “biofertilizer,” which should be addressed to improve conceptual clarity.
• In Section 2, the well-established modes of action of several species as plant growth promoters and as protectors against abiotic stress should be provided, rather than focusing primarily on some issues related to the use of these microorganisms.
• In Section 3, the extensive reference to the effects of certain bacteria (non-cyanobacteria) should be removed and focus on the knowledge about the microalgae/cyanobacteria.

 

Minor points

• Line 24 – “certain species possess the capacity to fix atmospheric nitrogen,…” – should stress that this refers only to cyanobacteria!
• Line 62 – “microalgae and cyanobacteria are unicellular …” –  Are microscopic, but not always unicellular!
• Line 85 – the number of the reference should be included
• Line 159-161- Is this s biostimulant effect or biofertilizer as it adds large amounts of nutrients to the soil?
• Line 228-229 – “effective as biofertilizers in salt-affected soils, …” – It's in the biostimulants section, but referred to as biofertilizer effect. It is indeed a biostimulant effect!
• Line 258-259- If it provides nutrient is a biofertilizer effect.
• Line 295 – “synthesizing plant hormones,…” – is a biostimulants , not a biofertilizer, effect.
• Line 405-406 – “biofertilizers that can promote plant growth through phytohormone production are known as phytostimulators.” – but are in the biofertilizer section!

Author Response

(The point-by-point response is also in the attachment)

We sincerely thank the reviewer for their thoughtful comments and constructive suggestions. Their observations have been extremely valuable in improving the clarity, scientific depth, and overall quality of the manuscript. We have carefully considered all of the points raised and revised the text accordingly, which we believe has significantly strengthened the work. We are grateful for the time and effort the reviewer dedicated to evaluating our study

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REVIEWER COMMENTS 

REVIEWER #1

[Comment 1] The manuscript by Flores et al., “Microalgae and cyanobacteria and their application in agriculture: natural-based biofertilizers, biostimulants and biocontrol compounds”, provides a comprehensive review of the current knowledge on the potential and applications of microalgae and cyanobacteria in sustainable agriculture. It is well structured and written, summarising the key traits of these microorganisms in relation to plant growth promotion and soil fertility improvement. The work also compiles information on commercially available products derived from these microorganisms and highlights the knowledge gaps and challenges that need to be addressed to enhance their agricultural use. However, some points could be further refined to enhance the overall quality of the work.

[Response 1] We sincerely thank the Reviewer for the positive and encouraging evaluation of our manuscript. We greatly appreciate the acknowledgment of the structure, clarity, and scope of our review, as well as the recognition of our efforts in compiling relevant information on commercially available products and identifying knowledge gaps. We have carefully addressed the points suggested for refinement, and the corresponding changes have been incorporated into the revised version to further improve the quality and clarity of the manuscript.

Major points:

[Comment 2] The manuscript would benefit from a clear definition of “biofertilizer” and a concise explanation of how it differs from “biostimulants” from the authors’ perspective.

Standardise the definition of “microalga,” as in some sections both microalgae and cyanobacteria are mentioned, whereas in others the term “microalgae” is used alone to encompass both eukaryotic microalgae and cyanobacteria.

These two aspects should be clarified early on throughout the introduction.

[Response 2] Following the reviewer’s advice, we have revised the introduction to provide a clear and precise definition of both and “biostimulant” (lines 76-79) and “biofertilizer” (lines 100-101):

“In agriculture, a biostimulant is defined as a substance or microorganism that, when applied in small amounts, stimulates natural processes to enhance nutrient uptake ef-ficiency, tolerance to abiotic stress, and/or crop quality, regardless of its nutrient content”

“Microalgae and cyanobacteria address this need by acting as biofertilizers that colonize the plant rhizosphere or tissues and enhance nutrient uptake”

In addition, we have standardized the terminology throughout the manuscript. We now explicitly use “microalgae and cyanobacteria” when referring to both groups, and in certain contexts, we use “photosynthetic microorganisms” when appropriate. This change avoids ambiguity and makes it clear that we are addressing two distinct, yet functionally overlapping, groups.

[Comment 3] Sections 2 and 3 exhibit some inconsistencies in the application of the terms “biostimulant” and “biofertilizer,” which should be addressed to improve conceptual clarity.

[Response 3] We appreciate the reviewer’s valuable comment. Minor adjustments have been implemented in both sections to clearly differentiate biostimulants from biofertilizers. To avoid ambiguity, each section now begins with a precise definition of the respective term. Additionally, Section 3.5 Phytostimulators has been removed, and its content has been integrated into Section 2, ensuring consistency and preventing potential misunderstandings.

[Comment 4] In Section 2, the well-established modes of action of several species as plant growth promoters and as protectors against abiotic stress should be provided, rather than focusing primarily on some issues related to the use of these microorganisms.

[Response 4] We agree with the reviewer’s observation. To address this point, we have introduced a new subsection specifically dedicated to the different modes of action (line 269; Section 2.1. Modes of action and mechanisms of microalgae- and cyanobacteria-derived biostimulants). We have also added separate subsections presenting concrete examples (Sections 2.2, 2.3, and 2.4), which highlight the diverse species applied in agricultural contexts. This restructuring broadens the scope of the manuscript and provides a clearer, more conceptually focused presentation of the modes of action.

[Comment 5] In Section 3, the extensive reference to the effects of certain bacteria (non-cyanobacteria) should be removed and focus on the knowledge about the microalgae/cyanobacteria.

[Response 5] We agree with the reviewer’s comment. Section 3 has been completely reorganized to ensure that the focus remains on the current knowledge regarding microalgae and cyanobacteria.

Minor points

[Comment 6]  Line 24 – “certain species possess the capacity to fix atmospheric nitrogen,…” – should stress that this refers only to cyanobacteria!

[Response 6] The term cyanobacteria has been added to this sentence to ensure clarity and accuracy (line 25).

“Additionally, several cyanobacterial species can fix atmospheric nitrogen, further enhancing their agricultural relevance.”

[Comment 7]  Line 62 – “microalgae and cyanobacteria are unicellular …” –  Are microscopic, but not always unicellular!

[Response 7] We thank the reviewer for this observation. The term unicellular has been removed. Moreover, as the introduction was reorganized during the revision process, the sentence in question has been modified accordingly.

[Comment 8]  Line 85 – the number of the reference should be included

[Response 8] Done. The reference has been now inserted in line 85 (reference 5).

[Comment 9]  Line 159-161- Is this s biostimulant effect or biofertilizer as it adds large amounts of nutrients to the soil?

[Response 9] We agree with the reviewer that, in this case, the plant growth–promoting effect could result from a combination of biofertilization and biostimulation, given that these organisms contribute substantial amounts of nutrients to the soil. To avoid potential misinterpretation, the sentence has been revised as follows (line 187):

“Algae are recognized as some of the earliest plant growth promotion compounds used in agriculture, with historical records dating back to the Roman era, where they were applied as manure to enrich soil fertility and promote plant growth, an application that has continued through the centuries.”

[Comment 10]  Line 228-229 – “effective as biofertilizers in salt-affected soils, …” – It's in the biostimulants section, but referred to as biofertilizer effect. It is indeed a biostimulant effect!

[Response 10] We agree with the reviewer and apologize for the misinterpretation. To ensure accuracy, the term biofertilizer has been replaced with biostimulant in the revised manuscript in line 374.

[Comment 11]  Line 258-259- If it provides nutrient is a biofertilizer effect.

[Response 11] This sentence has been removed to avoid misinterpretation.

[Comment 12]  Line 295 – “synthesizing plant hormones,…” – is a biostimulants , not a biofertilizer, effect.

[Response 12] Done. Concept has been removed.

[Comment 13]  Line 405-406 – “biofertilizers that can promote plant growth through phytohormone production are known as phytostimulators.” – but are in the biofertilizer section!

[Response 13] We agree with the reviewer. This section has been removed in the revised manuscript, and its content has been incorporated into the reorganized Section 2 to enhance clarity, coherence, and consistency.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors reviewed the current applications, market, technological constraints, and research gaps of microalgae- and cyanobacteria-based products in agriculture field. The topic holds potential for future application of bio-based fertilizer and biocontrols in sustainable agriculture. However, it is not acceptable in its current form. My major concerns are:

• It seems that the contents are combined by independent parts, instead of linking them together. For example, in introduction, the repetition of introducing microalgae and cyanobacteria (paragraphs started from Lines 58, 71). In section 3, almost the whole section (except for 3.6) is centered at the biofertilizers using beneficial microorgainsms (like PGPR), while failed to incorporate the role of microalgae and cyanobacteria within each section, respectively. Although the authors discuss the microalgae and cyanobacteria in biofertilizer field in section 3.6, it seems isolated from previous contents and should be revised thoroughly.
• A lot of key statement with a wide variety of species and background environments usually have only one or no reference, perhaps due to multiple participation of original draft writing? Anyhow, this is not appropriate. Such statement should be avoided or cited correctly.
• Many empirical evidences of the functional/metabolic role of microalgae and cyanobacteria were summarized from literatures that conducted under non-soil environment, pls check the main text thoroughly and be careful when draw the conclusion of their applications in farmlands
• The illustration is rather weak to explain the main points listed in the main text. For example, in Fig. 1, on the left we can see the microalgae-based products, however, I cannot see their application value on the right panel with four plants (why these four plants?). Moreover, the text on the right-bottom corner mentioned about bottleneck and perspectives, but only listed the forms of microalgae-based products. The title is “Illustration as an overview of the present revision.” Pls improve this title the figure legend to be more informative, and make a double check, do you mean present review? Same applies to the figure 2, the information is very limited and not clear to me. Pls improve these figures very carefully.
• In addition, the authors should consider add one more figure for section 2, as they indicated in Line 173-174 “selecting the most effective and suitable strains remains a complex task.” and Line 184 “a decision-making matrix for strain selection should integrate both production performance and biochemical profiles.” Since this is directive section, pls make an informative figure to illustrate how to make an appropriate and efficient solution (e.g., strain growth ability, environmental condition, species dependency, cost-effective, application form, environmental impacts, etc). I would also suggest to divide section 2 into several subsections, just like section 3 and section 4.
• For Table 1 and table 2, 3, pls add the detailed information of these species when used as biofertilizer and bioagents, including the location of the study, the form of products, study duration, host plant species, soil type, pH, climate conditions, etc. for now, it is too simple and does not meet the criteria of an academic review

Other comments:

Line 36-56, pls consider combine these two paragraphs as one to show the background in more direct way and propose the use of microalgae and cyanobacteria earlier at the second paragraph.

Line 66, 70, there should be more than just one reference for such statement

Line 81, add the reference after “depending on the crop needs and environmental conditions

Line 94, line 111-114, line 126 ongoing advances, line 189-191, Line 406-409, same here, add the refs, pls also check other similar issues in the main text

Line 138 Whether these prospects were ideally covered in the following section? pls check and improve such statement

Line 173, remains complex? How ?

Line 184, decision-making matrix, be more specific

Line 277, rhizobacteria, should be revised to microorganisms, as there should be beneficial m in other niches

L 299. Very limited information on N-fixing fertilizer using microalgae and cyanobacteria, this section and the follow-up section should be revised

L 465 pls improve the table accordingly

Line 467: It seems like section 4 is focused on the microalgae instead of cyanobacteria? Such as 4.2. Microalgae as herbicides 4.3. Microalgae as insecticides

Line 584: for this section, the authors should consider summarizing the challenges and pitfalls in each previous section accordingly. For instance, pls be more direct to inform the farmers how to select the most relevant microalgae products for improving crop production in a sustainable and economically friendly way

 

Author Response

(The point-by-point response is also in the attachment)

We sincerely thank the reviewer for their thoughtful comments and constructive suggestions. Their observations have been extremely valuable in improving the clarity, scientific depth, and overall quality of the manuscript. We have carefully considered all of the points raised and revised the text accordingly, which we believe has significantly strengthened the work. We are grateful for the time and effort the reviewer dedicated to evaluating our study

***********************************

REVIEWER #2

[Comment 1]  It seems that the contents are combined by independent parts, instead of linking them together. For example, in introduction, the repetition of introducing microalgae and cyanobacteria (paragraphs started from Lines 58, 71).

[Response 1] We thank the reviewer for this insightful comment. Following the suggestion, we have revised the manuscript to improve coherence between sections, ensuring that the content is more clearly linked. In particular, the introduction has been streamlined to avoid repetition regarding the presentation of microalgae and cyanobacteria (former paragraphs starting at Lines 58 and 71), resulting in a more cohesive and integrated narrative.

[Comment 2]  In section 3, almost the whole section (except for 3.6) is centered at the biofertilizers using beneficial microorgainsms (like PGPR), while failed to incorporate the role of microalgae and cyanobacteria within each section, respectively. Although the authors discuss the microalgae and cyanobacteria in biofertilizer field in section 3.6, it seems isolated from previous contents and should be revised thoroughly.

[Response 2] We thank the reviewer for raising this point, which was also noted by other reviewers. Following their advice, Section 3 has been thoroughly reorganized and now focuses primarily on the role of microalgae and cyanobacteria as biofertilizers, while including some examples of non-photosynthetic organisms for context.

[Comment 3]  A lot of key statement with a wide variety of species and background environments usually have only one or no reference, perhaps due to multiple participation of original draft writing? Anyhow, this is not appropriate. Such statement should be avoided or cited correctly.

[Response 3] We thank the reviewer for this valuable comment. Following the suggestion, we have added additional references to the tables and carefully revised the manuscript to ensure that all key statements are properly supported and appropriately cited.

[Comment 4]  Many empirical evidences of the functional/metabolic role of microalgae and cyanobacteria were summarized from literatures that conducted under non-soil environment, pls check the main text thoroughly and be careful when draw the conclusion of their applications in farmlands

[Response 4] We thank the reviewer for the comment. A new column has been introduced in Table 1 and Table 2 to specify whether the study was conducted in a soil or non-soil environment, and several other minor changes have been made throughout the text accordingly.

[Comment 4]  The illustration is rather weak to explain the main points listed in the main text. For example, in Fig. 1, on the left we can see the microalgae-based products, however, I cannot see their application value on the right panel with four plants (why these four plants?). Moreover, the text on the right-bottom corner mentioned about bottleneck and perspectives, but only listed the forms of microalgae-based products. The title is “Illustration as an overview of the present revision.” Pls improve this title the figure legend to be more informative, and make a double check, do you mean present review? Same applies to the figure 2, the information is very limited and not clear to me. Pls improve these figures very carefully.

[Response 4]  We thank the reviewer for the constructive feedback regarding the figures. Figure 1 has been revised according to the suggestions to improve clarity and to better illustrate the main points discussed in the text. The title and legend have also been corrected and expanded to provide a more informative overview of the present review. In addition, Figure 2 has been replaced with Table 3, which now details the different molecules produced, their modes of action, and the corresponding references, thereby providing clearer and more comprehensive information.

[Comment 5]  In addition, the authors should consider add one more figure for section 2, as they indicated in Line 173-174 “selecting the most effective and suitable strains remains a complex task.” And Line 184 “a decision-making matrix for strain selection should integrate both production performance and biochemical profiles.” Since this is directive section, pls make an informative figure to illustrate how to make an appropriate and efficient solution (e.g., strain growth ability, environmental condition, species dependency, cost-effective, application form, environmental impacts, etc). I would also suggest to divide section 2 into several subsections, just like section 3 and section 4.

[Response 5] Following the reviewer’s suggestion, we have included a new figure (Figure 2 in the revised manuscript) to illustrate the decision-making process for strain selection, integrating key factors such as growth ability, environmental conditions, species dependency, cost-effectiveness, application form, and environmental impacts. In addition, Section 2 has been reorganized into diferent subsections to provide a clearer and more structured presentation, consistent with Sections 3 and 4.

[Comment 6]  For Table 1 and table 2, 3, pls add the detailed information of these species when used as biofertilizer and bioagents, including the location of the study, the form of products, study duration, host plant species, soil type, pH, climate conditions, etc. for now, it is too simple and does not meet the criteria of an academic review

[Response 6] Table 1 has been extended with additional references and examples of microalgae and cyanobacteria species used in biofertilization. Furthermore, detailed information has been added, including the host plant species and the type of screening (in vitro, in vivo, or greenhouse). Regarding Table 2, new columns have been incorporated to indicate the underlying mechanisms of biocontrol, the potential target pests, and whether the study was conducted in vivo or in vitro. Finally, Table 4 (former Table 3) has been updated with additional references.

[Comment 7]  Line 36-56, pls consider combine these two paragraphs as one to show the background in more direct way and propose the use of microalgae and cyanobacteria earlier at the second paragraph.

[Response 7] Done. These two paragraphs have been combined into a single, more concise paragraph that presents the background in a direct manner.

[Comment 8]  Line 66, 70, there should be more than just one reference for such statement

[Response 8] Done. Additional relevant references have been added to this statement:

15. Osathanunkul, M.; Thanaporn, S.; Karapetsi, L.; Nteve, G.M.; Pratsinakis, E.; Stefanidou, E.; Lagiotis, G.; Avramidou, E.; Zorxzobokou, L.; Tsintzou, G.; et al. Diversity of Bioactive Compounds in Microalgae: Key Classes and Functional Applications. Mar Drugs 2025, 23.
16. Chiaiese, P.; Corrado, G.; Colla, G.; Kyriacou, M.C.; Rouphael, Y. Renewable Sources of Plant Biostimulation: Microalgae as a Sustainable Means to Improve Crop Performance. Front Plant Sci 2018, 871.

[Comment 9]  Line 81, add the reference after “depending on the crop needs and environmental conditions

[Response 9] This sentence is no longer present in the introduction, as the section has been reorganized in response to the reviewers’ comments.

[Comment 10]  Line 94, line 111-114, line 126 ongoing advances, line 189-191, Line 406-409, same here, add the refs, pls also check other similar issues in the main text

[Response 10] The reference list has been revised and expanded in response to the reviewers’ comments. A total of 23 new references were incorporated, raising the overall number of citations to 168 references. This update ensures that the manuscript reflects the most relevant and recent research contributions in the field, directly addressing the feedback provided by the reviewers.

• Line 94 (line 100 in the corrected version of the manuscript) – highlighting the utilization of cyanobacteria for nitrogen fixation

Lorenzi, A.S.; Chia, M.A. Cyanobacteria’s Power Trio: Auxin, Siderophores, and Nitrogen Fixation to Foster Thriving Agriculture. World J Microbiol Biotechnol 2024,

Nawaz, T.; Saud, S.; Gu, L.; Khan, I.; Fahad, S.; Zhou, R. Cyanobacteria: Harnessing the Power of Microorganisms for Plant Growth Promotion, Stress Alleviation, and Phytoremediation in the Era of Sustainable Agriculture. Plant Stress 2024, 11.

• Line 111-114, line 126 ongoing advances References have been added

Novoveská, L.; Nielsen, S.L.; Eroldoğan, O.T.; Haznedaroglu, B.Z.; Rinkevich, B.; Fazi, S.; Robbens, J.; Vasquez, M.; Einarsson, H. Overview and Challenges of Large-Scale Cultivation of Photosynthetic Microalgae and Cyanobacteria. Mar Drugs 2023, 21

• Lines 189–191.

Jithesh, M.N.; Shukla, P.S.; Kant, P.; Joshi, J.; Critchley, A.T.; Prithiviraj, B. Physiological and Transcriptomics Analyses Reveal That Ascophyllum nodosum Extracts Induce Salinity Tolerance in Arabidopsis by Regulating the Expression of Stress Responsive Genes. J Plant Growth Regul 2019, 38, 463–478, doi:10.1007/s00344-018-9861-4.

Singh, J.S.; Kumar, A.; Rai, A.N.; Singh, D.P. Cyanobacteria: A Precious Bio-Resource in Agriculture, Ecosystem, and Environmental Sustainability. Front Microbiol 2016, 7.

Nishanth, S.; Kokila, V.; Prasanna, R. Metabolite Profiling of Plant Growth Promoting Cyanobacteria—Anabaena laxa and Calothrix elenkinii, Using Untargeted Metabolomics. 3 Biotech 2024, 14, doi:10.1007/s13205-023-03902-7.

[Comment 11]  Line 138 Whether these prospects were ideally covered in the following section? pls check and improve such statement

[Response 11] We thank the reviewer for this observation. This statement has been revised as part of the modifications made to the introduction, considering not only this comment but also the references and suggestions provided by the other reviewers.

[Comment 12]  Line 173, remains complex? How ?

[Response 12] Following the reviewer’s advice, this sentence has been further developed to explain in greater detail why strain selection represents a complex task in the design of biostimulants (line 196-203). The revised text elaborates on key factors such as the need for well-characterized strains with high productivity of target bioactive compounds, ease of large-scale cultivation, adaptability to diverse environmental conditions, and compatibility with existing agricultural practices. Moreover, a figure has been also added to explain better the concept (Figure 1).

“Although microalgae and cyanobacteria hold great promise for agricultural applications, the selection of the most effective and context-appropriate strains remains a challenging task. This process requires access to well-characterized strains with a demonstrated high capacity for producing target bioactive compounds of agricultural relevance, while also being amenable to cost-effective, large-scale cultivation. Additionally, strains should exhibit adaptability to variable environmental conditions, stable productivity over time, and compatibility with existing agricultural practices to ensure practical implementation and long-term sustainability”

[Comment 13]  Line 184, decision-making matrix, be more specific

[Response 13] This sentence has been revised following the reviewer’s suggestion, specifying some of the most important parameters to be considered in the decision-making matrix (213-219).

“In practice, an effective decision-making matrix for strain selection should integrate both production performance metrics—such as growth rate, biomass yield, and cultivation efficiency—and detailed biochemical profiles, including the concentration and diversity of target bioactive compounds. This integrated approach enables the systematic comparison of candidate strains, ensuring that the final selection balances productivity, functional quality, and suitability for large-scale, cost-effective biostimulant development”

[Comment 14]  Line 277, rhizobacteria, should be revised to microorganisms, as there should be beneficial m in other niches

[Response 14] Done. This terminology has been changed to PGPB, referring now to Plant growth-promoting bacteria.

[Comment15]  L 299. Very limited information on N-fixing fertilizer using microalgae and cyanobacteria, this section and the follow-up section should be revised

[Response 15] The section on nitrogen-fixing fertilizers derived from cyanobacteria has been expanded to include additional background information and new illustrative examples of their applications. These examples highlight recent advances and practical uses in agricultural systems. The revisions are incorporated into Section 3 of the manuscript, for examples Lines 504–510 and 513–522 of the revised version.

[Comment 16]  L 465 pls improve the table accordingly

[Response 16] Table 1 has been improved by incorporating additional references and updated information to enhance its accuracy and completeness.

[Comment 17]  Line 467: It seems like section 4 is focused on the microalgae instead of cyanobacteria? Such as 4.2. Microalgae as herbicides 4.3. Microalgae as insecticides

[Response 17] Section 4 includes examples of both microalgae and cyanobacteria. To avoid confusion, the section title has been adjusted accordingly to better reflect its content.

[Comment 18]  Line 584: for this section, the authors should consider summarizing the challenges and pitfalls in each previous section accordingly. For instance, pls be more direct to inform the farmers how to select the most relevant microalgae products for improving crop production in a sustainable and economically friendly way

[Response 18] Following the reviewer’s advice, a new Figure 3 has been added to the manuscript. This figure presents a graphical summary box highlighting the main criteria for selecting microalgae- and cyanobacteria-based products, aimed at guiding users toward sustainable and economically viable choices for improving crop production.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The overall manuscript is well-written, focusing on the microalgae and cyanobacteria in sustainable agriculture. The review motivation and novelty statement are not stated properly. The following are the specific comments to improve the manuscript quality before further proceeding:

1. The title should be revised. I recommend amending two features, such as mechanistic insight and key research gaps in the revised title. A title should be lucrative and have the key features of the paper.
2. In the abstract, the review process and motivation should be added. Why is this review needed? As biostimulants, bacteria and fungi are well-explored by previous studies. Why are microalgae and cyanobacteria still relevant for this purpose?
3. The author should augment a strong hypothesis concerning microalgae and cyanobacteria over available biostimulants. In particular, the vital research gap and review motivation should be amended.
4. In addition, a review methodology is highly recommended. What searching tools and search engines are used, and how many papers are searched, etc.? This should be a new segment after the introduction or should be embedded with the introduction.
5. In section 3, lines 275-392, this section and sub-sections are found to be the potential redundancy of earlier papers and not directly related to microalgae and cyanobacteria. This section should be revised or squeezed, and the related discussion should be amended as further segments such as "Microalgae consortia" or advancement of microalgae studies.
6. For the Figure 2 caption, please cite the related reference if you adapt the information from previous papers.
7. In Table 2, amend the underlying mechanism of biocontrol.
8. In Table 3, add the source of information.
9. Revise the title of section 6, line 584, Bottlenecks and future perspectives, as "Research bottlenecks and future perspectives. Add the research gaps as bullet points.
10. The conclusion is poorly written. Please revise the conclusion in terms of key findings and vital recommendations.
11.  

Author Response

We sincerely thank the reviewer for their thoughtful comments and constructive suggestions. Their observations have been extremely valuable in improving the clarity, scientific depth, and overall quality of the manuscript. We have carefully considered all of the points raised and revised the text accordingly, which we believe has significantly strengthened the work. We are grateful for the time and effort the reviewer dedicated to evaluating our study

 

REVIEWER #3

[Comment 1]  The title should be revised. I recommend amending two features, such as mechanistic insight and key research gaps in the revised title. A title should be lucrative and have the key features of the paper.

[Response 1] We thank the reviewer for this valuable suggestion. In accordance with his comment, the title has been revised to:
" Harnessing Microalgae and Cyanobacteria for Sustainable Agriculture: Mechanistic Insights and Applications as Biostimu-lants, Biofertilizers and Biocontrol Agents."

[Comment 2]  In the abstract, the review process and motivation should be added. Why is this review needed? As biostimulants, bacteria and fungi are well-explored by previous studies. Why are microalgae and cyanobacteria still relevant for this purpose?

[Response 2] The abstract has been revised to emphasize the limited research on microalgae and cyanobacteria in this field and to clearly highlight this gap, aligning it with the scope and focus of the manuscript (line 17, lines 57-61 in the introduction)

[Comment 3]  The author should augment a strong hypothesis concerning microalgae and cyanobacteria over available biostimulants. In particular, the vital research gap and review motivation should be amended.

[Response 3] Following the reviewer advice the following information has been added to the introduction section (lines 87-92):

“Compared to other commonly used biostimulants such as plant extracts, humic substances, or microbial inoculants based on bacteria and fungi, microalgae and cyano-bacteria offer unique advantages. Their capacity to synthesize a wide range of bioactive metabolites, their high metabolic plasticity, and, in the case of some cyanobacteria, their ability to fix atmospheric nitrogen, enable them to function simultaneously as biofertilizers, biostimulants, and biocontrol agents.”

[Comment 4]  In addition, a review methodology is highly recommended. What searching tools and search engines are used, and how many papers are searched, etc.? This should be a new segment after the introduction or should be embedded with the introduction.

[Response 4] The manuscript is a review article about the applications of microalgae and cyanobacteria in agriculture and is not methodological in nature; therefore, a methodology section is not contemplated in the author instructions for this type of work. However, we agree with the reviewer that including this information is valuable. Accordingly, we have incorporated it into the introduction by adding a sentence that specifies the in-depth bibliographic search we conducted (line 155).

[Comment 5]  In section 3, lines 275-392, this section and sub-sections are found to be the potential redundancy of earlier papers and not directly related to microalgae and cyanobacteria. This section should be revised or squeezed, and the related discussion should be amended as further segments such as "Microalgae consortia" or advancement of microalgae studies.

[Response 5] We thank the reviewer for raising this point, which was also noted by other reviewers. In the revised version of the manuscript, Section 3 has been completely reorganized to focus specifically on the use of microalgae and cyanobacteria. Additionally, a new subsection on Microalgae consortia has been incorporated into Section 2 to further strengthen the discussion and highlight recent advancements in this area.

[Comment 6]  For the Figure 2 caption, please cite the related reference if you adapt the information from previous papers.

[Response 6] We appreciate the reviewer’s observation. Figure 2 was originally created de novo for this manuscript and not adapted from previous papers. However, in line with the constructive suggestions from other reviewers, we have decided to remove this figure. Instead, we have included a detailed summary table at the end of the section, which we believe provides a clearer and more comprehensive presentation of the information.

[Comment 7]  In Table 2, amend the underlying mechanism of biocontrol.

[Response 7] The underlying mechanisms of biocontrol have been added to Table 2, along with additional examples and information, including the potential target pathogens/pests and the type of experimental evidence.

[Comment 8]  In Table 3, add the source of information.

[Response 8] References and link to the website of the commercialized microalgae- and cyanobacteria-based products are now included.

[Comment 9]  Revise the title of section 6, line 584, Bottlenecks and future perspectives, as "Research bottlenecks and future perspectives. Add the research gaps as bullet points.

[Response 9] Following the reviewer’s comment, the title of this section has been revised accordingly, and a new Figure 3 has been added. This figure presents the research gaps as concise bullet points, helping the reader quickly identify the main challenges in the development and application of microalgae- and cyanobacteria-based products in agriculture.

[Comment 10]  The conclusion is poorly written. Please revise the conclusion in terms of key findings and vital recommendations.

[Response 10] The conclusion has been revised and expanded to highlight the key findings of the review and to provide clear and concise recommendations, in line with the reviewer’s suggestion.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have done an excellent job revising their earlier manuscript. The improvements in the tables and figures are particularly noteworthy.

However, my main concern relates to the distinction made by the authors between biostimulants and biofertilizers. I assumed, by the examples of each along the text, that in the author's opinion, fertilisers primarily supply essential nutrients to plants, whereas biostimulants act by enhancing plant physiological processes. However, the difference between these two concepts is not clearly defined in the text. In the introduction, the authors introduce the term biostimulator; however, the concept of biofertilizer is only mentioned later, in lines 180–181. I remain unconvinced by the definition of biofertilizer adopted here (a substance containing microorganisms known as plant growth-promoting bacteria).

A minor point: In 3.1. the authors should focus on the nitrogen fixation and plant N supply, and leave the siderophore production and P solubilization to the specific points 3.2 and 3.3.

Author Response

(The point-by-point response can also be found in the attached document)

 

Dear Reviewers,

We sincerely thank you for the time and effort you dedicated to reviewing our manuscript. Your constructive comments and suggestions were extremely valuable, and we believe that the revisions made in response have significantly improved the quality and clarity of the work.

Sincerely,
Gloria Torres Cortés

REVIEWER COMMENTS 

REVIEWER #1

[Comment 1] The authors have done an excellent job revising their earlier manuscript. The improvements in the tables and figures are particularly noteworthy.

[Response 1] We sincerely thank the Reviewer for their positive evaluation and encouraging feedback. We greatly appreciate the acknowledgment of the improvements made to the tables and figures, and we are pleased that the revisions have strengthened the manuscript.

[Comment 2]  However, my main concern relates to the distinction made by the authors between biostimulants and biofertilizers. I assumed, by the examples of each along the text, that in the author's opinion, fertilisers primarily supply essential nutrients to plants, whereas biostimulants act by enhancing plant physiological processes. However, the difference between these two concepts is not clearly defined in the text. In the introduction, the authors introduce the term biostimulator; however, the concept of biofertilizer is only mentioned later, in lines 180–181. I remain unconvinced by the definition of biofertilizer adopted here (a substance containing microorganisms known as plant growth-promoting bacteria).

[Response 2] We sincerely thank the Reviewer for this valuable comment. Following this suggestion, the concept of biofertilizers has now been introduced more clearly in the introduction (lines 102–104), where it reads:

“Biofertilizers are natural preparations containing living microorganisms or other natural substances that, when applied to seeds, plant surfaces, or soil, promote plant growth by increasing the supply or availability of essential nutrients [27].”

In addition, the definition has been refined later in the manuscript (lines 427–430), where it reads:

“A biofertilizer is a substance containing specific microorganisms or other natural preparations that, when applied to seeds, plant surfaces, or soil, promote plant growth by increasing the supply or availability of essential nutrients [27]. These microorgan-isms or preparations improve plant growth by …”

[Comment 3]  A minor point: In 3.1. the authors should focus on the nitrogen fixation and plant N supply, and leave the siderophore production and P solubilization to the specific points 3.2 and 3.3.

[Response 3] We sincerely thank the Reviewer for their appreciation. Following this suggestion, some of the content in Section 3.1 referring to phosphorus and siderophore production has been moved to Sections 3.2 and 3.3, respectively. Specifically:

Lines 569–571 have been moved from Section 3.1 to Section 3.2, Microalgae and cyanobacteria as biofertilizers: nutrient solubilization, and now read as follows:

“In addition, both microalgae can stimulate root growth through auxin-like activity while contributing to the mobilization or improved uptake of phosphorus and potas-sium, leading to better growth under nutrient-limited or stress environments”

Lines 610–615 have been moved from Section 3.1 to Section 3.3, Microalgae and cyanobacteria as biofertilizers: siderophore-mediated growth promotion, and now read as follows:

“Moreover, in relation to the Cyanobacteria spp, Brick et al., in 2025 [126] highlighted the significant potential of Synechococcus mundulus-derived siderophore in stimulating Zea mays physicochemical growth parameters and iron uptake. The results of this study indicate the capacity of cyanobacteria to synthesize siderophores as a sustainable sub-stitute for synthetic iron chelators, and their role in the management of plant stress”

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I appreciate the detailed revision from the authors. Just one minor suggestion: in section 2.2, there are several subtitles such as "1. Enhancement of Nutrient Uptake and Assimilation", the number should be changed to avoid repetition and confusion. You may use (1), (2), etc. instead.

Author Response

(The point-by-point response can also be found in the attached document)

Dear Reviewers,

We sincerely thank you for the time and effort you dedicated to reviewing our manuscript. Your constructive comments and suggestions were extremely valuable, and we believe that the revisions made in response have significantly improved the quality and clarity of the work.

Sincerely,

Gloria Torres Cortés

REVIEWER #2

[Comment 1]  I appreciate the detailed revision from the authors. Just one minor suggestion: in section 2.2, there are several subtitles such as "1. Enhancement of Nutrient Uptake and Assimilation", the number should be changed to avoid repetition and confusion. You may use (1), (2), etc. instead.

[Response 1] We sincerely thank the Reviewer for the positive and constructive comment. We appreciate the observation, which has helped us to improve the structure of section 2.2. Following the reviewer’s advice, the numbering in Section 2.2 has been revised to (1), (2), (3), etc., to avoid repetition and confusion.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The author have revised the manuscript  and addresses my concerns properly. This revised manuscirpt is suitable for publication.

Author Response

(The point-by-point response can also be found in the attached document)

Dear Reviewers,

We sincerely thank you for the time and effort you dedicated to reviewing our manuscript. Your constructive comments and suggestions were extremely valuable, and we believe that the revisions made in response have significantly improved the quality and clarity of the work.

Sincerely,

Gloria Torres Cortés

REVIEWER #3

[Comment 1] The author have revised the manuscript  and addresses my concerns properly. This revised manuscirpt is suitable for publication.

[[Response 1] We sincerely thank the Reviewer for their positive evaluation and for the constructive feedback provided throughout the review process. Their comments were very helpful in improving the clarity and overall quality of our manuscript, and we are grateful for their recommendation for publication.

Author Response File: Author Response.pdf