Magnetic Nanomaterials as Biocatalyst Carriers for Biomass Processing: Immobilization Strategies, Reusability, and Applications
Round 1
Reviewer 1 Report
The industrial interest in biomass conversion to produce biofuels and other valuable chemicals is growing exponentially. However, the application of enzymes on an industrial scale requires strategies to guide bioconversions practically and cost-effectively. The chemical designs related to magnetic systems with covalently linked or adsorbed enzymes are addressed in the manuscript and the overview about immobilized enzyme reusability. The authors present methods of synthesis for magnetic nanoparticles used as biocatalyst carriers for biomass conversion that include coprecipitation and thermal method, and enzyme immobilization strategies involving magnetic nanocarriers for biomass conversion. Immobilized enzymes show a longer half-life during storage, better tolerance against inhibitors, and changes in temperature and pH. Further, it has been shown that biobased materials as nanocarriers have great potential and promising results are obtained. Moreover, co-immobilization of multi-enzymes is announced as a prospective method. However, special attention has to be towards the toxicity and possible consequences of the nanomaterials released in the environment.
In general, the manuscript is well organized and the reported results are well summarised and clearly reported. For that reason, I suggest publishing in the present form.
Author Response
Thank you very much for your kind words, and recommendation.
Reviewer 2 Report
Mariño et al. give in their review an overview of state of the art on the use of magnetic nanoparticles as biocatalyst carriers for biomass processing. Due to the increasing interest of industry and society for biomass conversion in biofuels and other chemical products, developing simple strategies for these processes is highly relevant.
However, there are several recent reviews on (almost) the same topic, so I wonder why another one is needed.
In a simple search in the Web of Science, I found the following ones:
Title: Current Developments in Lignocellulosic Biomass Conversion into Biofuels Using Nanobiotechnology Approach
Author(s): Singhvi, M (Singhvi, Mamata); Kim, BS (Kim, Beom Soo)
Source: ENERGIES Volume: 13 Issue: 20 Article Number: 5300 DOI: 10.3390/en13205300 Published: OCT 2020
Title: Emerging role of nanocatalysts in the hydrolysis of lignocellulosic biomass leading to sustainable bioethanol production
Author(s): Rai, M (Rai, Mahendra); Ingle, AP (Ingle, Avinash P.); Pandit, R (Pandit, Raksha); Paralikar, P (Paralikar, Priti); Biswas, JK (Biswas, Jayanta Kumar); da Silva, SS (da Silva, Silvio Silverio)
Source: CATALYSIS REVIEWS-SCIENCE AND ENGINEERING Volume: 61 Issue: 1 Pages: 1-26 DOI: 10.1080/01614940.2018.1479503 Published: JAN 2 2019
Title: Advances in Nanocatalyst Design for Biofuel Production
Author(s): Zuliani, A (Zuliani, Alessio); Ivars, F (Ivars, Francisco); Luque, R (Luque, Rafael)
Source: CHEMCATCHEM Volume: 10 Issue: 9 Pages: 1968-1981 DOI: 10.1002/cctc.201701712 Published: MAY 9 2018
Title: Catalytic Conversion of Biomass into Chemicals and Fuels over Magnetic Catalysts
Author(s): Liu, B (Liu, Bing); Zhang, ZH (Zhang, Zehui)
Source: ACS CATALYSIS Volume: 6 Issue: 1 Pages: 326-338 DOI: 10.1021/acscatal.5b02094 Published: JAN 2016
The authors should comment on which important aspects and new insights are not covered by this recent review.
Regarding the introductory text on the magnetic properties „2. Synthesis of magnetic nanoparticles used as biocatalyst carriers for biomass conversion“, I have the impression that the authors are rather imprecise, e. g.
„They start to have superparamagnetic properties when nanoparticles are small enough…. “
„…the surface area available to enzyme binding is remarkably increased..“
„A fast response related to superparamagnetic behavior is due to a lower energy barrier ..“
For example, I do not understand to which system the magnetic particles are compared and what means small enough? For a non-expert in this field, this might be hard to follow.
The overview on the synthetic approaches for iron oxide nanoparticles is rather short, which would be, in principle, O. K., if appropriate references (especially to reviews) are given. The authors should refer here to more recent publications and not mainly to a more than a 10-year old review.
In the section „3.1. Immobilization and co-immobilization of Cellulose-degrading enzymes“, the authors give an extended overview on current magnetic particles-based approaches for such processes. The text is very long (more than four pages of pure text) and contains a lot of experimental details, which are extensively presented but not explained, compared and evaluated. Also, the properties and performance of the magnetic biocatalyst carriers are described in extended detail, but also here, explanations, comparisons, and validations are missing. The text is rather hard to read.
Some aspects like toxicology or colloidal stability of the nanoscopic immobilization systems are missing. From my point of view, this confuses the reader rather than providing a compact overview and clear assessments, which is, in my opinion, needed in a review article.
I would also suggest that more images (schematics, TEM images) of the presented immobilization systems are shown. This would help a reader who is not et an expert in this topic.
The results of this section are summarized in a long table, but the table is not well organized. It would be helpful if the table would be more structured and grouped in a meaningful way. E. g. the particle size in and magnetization, the number of catalytic cycles and the protein loading should be given and compared.
Sometimes the wording is rather unclear. E. g. the authors write about „APTES/TEOS-condensed Fe3O4NPs“ or „TEOS condensed“ particles. If tetraethoxysilane makes a condensation reaction, silica is also formed an APTES/ TEOS mixture condenses to amino-functionalized silica. There is also the option that some APTES molecules are bound onto the nanoparticle surface, but „TEOS condensed“ makes no sense because condensed TEOS is silica, so this should be descript in a chemically correct way. I also do not know what the authors mean by 2D graphene with layer-by-layer assembly in maghemite-magnetite and PAA brushes“ (in the same field in the table, the average size was obviously forgotten).
For the next sections, „3.2. Immobilization and co-immobilization of hemicellulose-degrading enzymes“, and „3.3. Immobilization of Lignin-degrading enzymes“, essentially the same criticism applies as for section 3.1, too many details, too unclear and, in my view, too little explanation, comparison and evaluation of the presented systems from the literature. Also, for the corresponding Tables 2 and 3a, similar criticism applies as for Table 1.
The authors should also explain all abbreviations, e. g. „Bmim“
In the section „4. Key factors of magnetic enzyme immobilization, “ the authors explain the importance of the colloidal stability of the magnetic particles. Why is this issue not discussed in sections 3.1 to 3.3 for the various presented examples, perhaps instead of extending experimental details?
In the „Conclusions and future perspectives, “ the authors mention the toxicity issue in this manuscript for the first time. I wonder why it is not more discussed, again already when the examples from the literature are presented in detail in sections 3.1 – 3.3.
Author Response
Reviewer: 2
Recommendation:
Comments:
Marino et al. give in their review an overview of state of the art on the use of magnetic nanoparticles as biocatalyst carriers for biomass processing. Due to the increasing interest of industry and society for biomass conversion in biofuels and other chemical products, developing simple strategies for these processes is highly relevant.
However, there are several recent reviews on (almost) the same topic, so I wonder why another one is needed.
In a simple search in the Web of Science, I found the following ones:
Title: Current Developments in Lignocellulosic Biomass Conversion into Biofuels Using Nanobiotechnology
Author(s): Singhvi, M (Singhvi, Mamata); Kim, BS (Kim, Beom Soo)
Source: ENERGIES Volume: 13 Issue:20 Article Number: 5300 DOI: 10.3390/en13205300 Published: OCT 2020
Title: Emerging roles of nanocatalysts in the hydrolysis of lignocellulosic biomass leading to sustainable bioethanol production.
Author(s): Zuliani, A (Zuliani, Alessio); Ivars, F (Ivars, Francisco); Luque, R (Luque, Rafael)
Source: CHEMCATCHEM Volume: 10 Issue: 9 Pages: 1968-1981 DOI: 10.1002/cctc.201701712 Published: MAY 9 2018
Title: Catalytic Conversion of Biomass into Chemicals and Fuels over Magnetic Catalysts
Author(s): Liu, B (Liu, Bing); Zhang, ZH (Zhang, Zehui)
Source: ACS CATALYSIS Volume: 6 Issue: 1 Pages: 326-338 DOI: 10.1021/acscatal.5b02094 Published: JAN 2016
The authors should comment on which important aspects and new insights are not covered by this recent review.
Answer: Thank you for the comments, suggestions and constructive criticism of the review manuscript. We agree that there are many review articles on similar topic. Nevertheless, review articles always bring insights on the topic from the authors point of view. Our manuscript brings the detail to synthesis of magnetic beads, their characteristics, toxicity, among other, but the emphasis was given on enzyme load and activity during reuse, because we aimed to show that enzyme@magnetic bead must be stable enough if wished to be successfully applied in day-a-day of bio-refinery. Thus, many details on biocatalysts, days of use, effectiveness, and robustness of tailored carriers were given, and as far as we know, this is the first article that presents those data. Our aims were not to criticise published articles, rather to revise and join interesting findings for enzymes possible industrial application. When appropriate, we have expressed our opinion on the best suited ways to use enzymes@magnetic supports.
Regarding the introductory text on the magnetic properties “2. Synthesis of magnetic nanoparticles used as biocatalyst carriers for biomass conversion”, I have the impression that the authors are rather imprecise, e.g.
“they start to have superparamagnetic properties when nanoparticles are small enough…”
“…the surface area available to enzyme binding is remarkably increased.”
“A fast response related to superparamagnetic behavior is due to a lower energy barrier..”
For example, I do not understand to which system the magnetic particles are compared and what means small enough? For a non-expert in this field, this might be hard to follow.
Answer: Thank you for bringing this to our attention. It has been amended in the manuscript.
The overview on the synthetic approaches for iron oxide nanoparticles is rather short, which would be, in principle, O.K., if appropriate references (especially to reviews) are given. The authors should refer here to more recent publications and not mainly to a more than 10-years old review.
Answer: Thank you for bringing this to our attention. The synthetic approaches were amended, with new references (review articles) added, as suggested.
In section “3.3. Immobilization and co-immobilization of cellulose-degrading enzymes”, the authors give an extended overview on current magnetic particles-based approaches for such processes. The text is very long (more than four pages of pure text) and contains a lot of experimental details, which are extensively presented but not explained, compared and evaluated. Also, the properties and performance of the magnetic biocatalyst carriers are described in extended detail, but also here, explanations, comparisons, and validations are missing. The text is rather hard to read.
Answer: Thank you. We have modified the text, accordingly.
Some aspects like toxicology or colloidal stability of the nanoscopic immobilization systems are missing. From my point of view, this confuses the reader rather than providing a compact overview and clear assessments, which is, in my opinion, needed in a review article. I would suggest that more images (schematics, TEM images) of the presented immobilization systems are shown. This would help a reader who is not an expert in this topic. The results of this section are summarized in a long table, but the table is not well organized. It would be helpful if the table would be more structured and grouped in a meaningful way. E.g. the particle size and magnetization, the number of catalytic cycles and the protein loading should be given and compared.
Answer: Thank you. We have modified the tables and tried to be more precise.
Sometimes the wording is rather unclear. E.e. the authors write about “APTE/TEOS-condensed Fe3O4NPs” or “TEOS condensed” particles. If tetraethoxysilane makes a condensation reaction, silica is also formed an APTES/TEOS mixtures condenses to amino-functionalized silica. There is also the option that some APTES molecules are bound onto the nanoparticles surface, but “TEOS condensed” makes no sense because condensed TEOS is silica, so this should be descript in a chemically correct way. I also do not know what the authors mean by 2D graphene with layer-by-layer assembly in maghemite-magnetite and PAA brushes” (in the same field in the table, the average size was obviously forgotten).
Answer: Thank you. We have modified the text and added the chemically correct description.
For the next sections “3.2. Immobilization and co-immobilization of hemicellulose-degrading enzymes” and “3.3. Immobilization of lignin-degrading enzymes”, essentially the same criticism applies as for section 3.1, too many details, too unclear and, in my view, too little explanation, comparison and evaluation of the presented systems from the literature. Also, for the corresponding Tables 2 and 3, similar criticism applies as for Table 1.
The authors should also explain all abbreviations, e.g. “Bmim”
Answer: Thank you for pointing this out. It has been corrected to “ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim][Cl])”
In section “4. Key factors of magnetic enzyme immobilization”, the authors explain the importance of the colloidal stability of the magnetic particles. Why is this issue not discussed in sections 3.1 to 3.3 for the various presented examples, perhaps instead of extending experimental details.
Answer: Thank you for bringing this to our attention. Colloidal stability was further discussed in the nanoparticle characterization section. Introduced changes are marked in color.
In the “Conclusions and future perspectives”, the authors mention the toxicity issue in this manuscript for the first time. I wonder why it is not more discussed, again already when the examples from the literature are presented in detail in sections 3.1 – 3.3.
Answer: Thank you for pointing this out. Toxicity is an important aspect in nanoparticles application. We added a paragraph introducing the topic at the nanoparticle characterization section. All changes are marked in color.
Once again, we appreciated the thorough analysis of our manuscript. We have made the corresponding corrections that we hope will meet with your approval.
Reviewer 3 Report
I would suggest adding a general scheme showing the synthetic approach to the presented subject. In general, the introduction lacks the clear goal of the review and do not show the tex paper is structured. What will be discussed in the paragraph? Moreover, the paragraphs do not show what is the main goal in biocatalysis using magnetic nanoparticles. What is the main aim to use them? Which parameter is the goal in biocatalysis? Where scientists should pay their attention? The paragraph about magnetic nanomaterials is weak. It is not a good introduction to magnetic nanoparticles either to the magnetic particles as support for biocayatalyst. I do not see papers from Teofil Jesniowski's group mention in the text. Their input to the field can not be neglected.
Author Response
Reviewer: 3
Recommendation:
Comments:
I would suggest adding a general scheme showing the synthetic approach to the presented subject. In general, the introduction lacks the clear goal of the review and do not show the text paper is structured. What will be discussed in the paragraph? Moreover, the paragraphs do not show what is the main goal in biocatalysis using magnetic nanoparticles. What is the main aim to use them? Which parameter is the goal in biocatalysis? Where should scientists pay their attention? The paragraph about magnetic nanomaterials is weak. It is not a good introduction to magnetic nanoparticles either to the magnetic particles as support for biocatalyst. I do not see papers from Teofill Jesniowski’s group mention in the text. Their input to the field cannot be neglected.
Answer: Thank you for the suggestions and critics. We have tried to explain better the aims of the review, as well as the importance of using the immobilised catalysts onto magnetic carriers. We have modified the introduction section, and explained the difficulties in applying enzymes in biomass processing, and the aims of exploring magnetic beads for enzyme use and recovery. We apologise for not using the articles by Prof. Jesiniowski's research group in the previous manuscript version, which are important for the biomass and waste water treatments, and modified the list of references according to citation in the text when appropriate.
Round 2
Reviewer 2 Report
The authors significantly improved and added to the manuscript as suggested by the reviewers.
The title of section 3.1, „Immobilization and co-immobilization of Cellulose-degrading enzymes silica-based“ should be changed, further the manuscript can be published in the present form.
Author Response
Thank you for the second round review, evaluation, and comments. The section 3.1 was renamed to:
Immobilization and co-immobilization of cellulose-degrading enzymes using silica-based carriers
Best regards,
Mayra, Stephanie and Ljubica
