Synthesis of Metal Nanoparticles by Microorganisms

Round 1

Reviewer 1 Report

Metal nanoparticles is a timely topic, and elucidating the mechanisms of their formation is still extremely challenging in many cases. Toxicity aspects very often put a limit to the use and production at industrial scale. The authors targeted the approach of microbial synthesis routes, and they give an excellently broad and deep overview of the current state of the art with respect to characterization techniques and their specific drawbacks. Specific examples are presented, which demonstrate the huge potential of this comparatively novel research field. This review, by carefully analyzing the current status of metal NPs, in particular those formed by microorganisms and the underlying molecular mechanisms of their synthesis, is certainly relevant for a broad variety of interdisciplinary research fields, especiall for materials science and biotechnology.

Author Response

Metal nanoparticles is a timely topic, and elucidating the mechanisms of their formation is still extremely challenging in many cases. Toxicity aspects very often put a limit to the use and production at industrial scale. The authors targeted the approach of microbial synthesis routes, and they give an excellently broad and deep overview of the current state of the art with respect to characterization techniques and their specific drawbacks. Specific examples are presented, which demonstrate the huge potential of this comparatively novel research field. This review, by carefully analyzing the current status of metal NPs, in particular those formed by microorganisms and the underlying molecular mechanisms of their synthesis, is certainly relevant for a broad variety of interdisciplinary research fields, especiall for materials science and biotechnology.

Response: Thank you for your meaning comments.

Reviewer 2 Report

Kato and Suzuki review papers that report successful synthesis of metal nanoparticle by microorganisms grown in normal temperature, pressure and culture medium with the objective of promoting environmentally friendly methods to produce nanoparticle for commercial and medicinal uses. The authors sort the paper by nano-particle type and summarise each paper they review as a paragraph, which makes reading the paper as a single unit very un-interesting. It is, however, a potentially very accessible way for readers to extract specific information and may be a very useful source. The paper is within the scope of the journal Crystals and I recommend its acceptance with very minor edits:

• The authors should use present rather than past tense when talking about this contribution (Lines 71, 115-124, 490).
• Line 132: replace “was” with “were”.
• Line 142: typo – “of by”
• The authors cite values with non-significant digits in several places along the paper. For example, in the tables and text citing references 43 and 49. There is no need to carry errors from those papers into the review paper.
• Line 438: remove the word “were”.

Author Response

Point 1: Kato and Suzuki review papers that report successful synthesis of metal nanoparticle by microorganisms grown in normal temperature, pressure and culture medium with the objective of promoting environmentally friendly methods to produce nanoparticle for commercial and medicinal uses. The authors sort the paper by nano-particle type and summarise each paper they review as a paragraph, which makes reading the paper as a single unit very un-interesting. It is, however, a potentially very accessible way for readers to extract specific information and may be a very useful source. The paper is within the scope of the journal Crystals and I recommend its acceptance with very minor edits:

Response 1: Thank you for your meaningful comments. We improved our manuscript according to your advice.

Point 2: The authors should use present rather than past tense when talking about this contribution (Lines 71, 115-124, 490).

Response 2: Thank you for your advice. We used present tense for this contribution at lines 71, 131-140 and 516.

Point 3: Line 132: replace “was” with “were”.

Response 3: We changed “was” to “were” at line 147.

Point 4: Line 142: typo – “of by”

Response 4: We corrected this mistake. We changed “of by” to “by” at line 157.

Point 5: The authors cite values with non-significant digits in several places along the paper. For example, in the tables and text citing references 43 and 49. There is no need to carry errors from those papers into the review paper.

Response 5: We showed one decimal place for the average size of NPs. For example, the average size of Ag NPs cited in reference 43 was changed to “ca. 30.7”.

Point 6: Line 438: remove the word “were”.

Response 6: Thank you for correcting the mistake. We removed the word of “were” at line 456.

Reviewer 3 Report

The manuscript from Kato and Suzuki focuses on the recent advances related to the synthesis of metal nanoparticles mediated by microorganisms. Although this topic has been reviewed largely, the decision to categorize the reviewed material upon the kinds of metals is an interesting approach.

As result, the review results quite interesting and it represents a potential useful tool for the researchers working in this field. Nonetheless, some major flaws have been identified and they should be addressed by the authors before to accept the manuscript for publication.

In general, for each section, too many examples and too little figures have been reported within.  As a consequence, sometime, the review looks like a ‘simple list’ of already published research works without a clear logical sequence. Furthermore, each section also presents a resume table that is a very useful tool for this purpose. Therefore, for each section, I suggest to shorten the written description and limit it only to the most relevant examples. More relevant figures must be included in order to clarify to the reader the exposed concepts. The figures could be extracted directly from the original publications (upon previous authorization). The summarizing tables should be reinforced and, regarding the latter, the header titles of each table columns are confusing and not proper. Please, change them.

As personal opinion, the section 4: ‘Metal nanoparticle synthesis by genetically modified bacteria’ does not enter into the main scope of the review as it introduces a different and relevant topic worth of a much deeper analysis.  In turn, I would suggest analysing and describing better the issue related to the NPs purification together with their potential applicability especially in biomedical application (e.g. the presence of endotoxins, cell debrises, etc etc)

Figure 3 is most proper of Introduction than Conclusions. Please, move it.

Author Response

Point 1: The manuscript from Kato and Suzuki focuses on the recent advances related to the synthesis of metal nanoparticles mediated by microorganisms. Although this topic has been reviewed largely, the decision to categorize the reviewed material upon the kinds of metals is an interesting approach.

As result, the review results quite interesting and it represents a potential useful tool for the researchers working in this field. Nonetheless, some major flaws have been identified and they should be addressed by the authors before to accept the manuscript for publication.

Response 1: Thank you for your reviews and comments. We improved and modified our manuscript according to your advice.

Point 2: In general, for each section, too many examples and too little figures have been reported within.  As a consequence, sometime, the review looks like a ‘simple list’ of already published research works without a clear logical sequence. Furthermore, each section also presents a resume table that is a very useful tool for this purpose. Therefore, for each section, I suggest to shorten the written description and limit it only to the most relevant examples. More relevant figures must be included in order to clarify to the reader the exposed concepts. The figures could be extracted directly from the original publications (upon previous authorization).

Response 2: Thank you for meaningful advice. We have shortened and summarized the whole sentence. In addition, we added some figures to section 3 for further understanding of readers. These figures would help the reader to understand the mechanisms of NPs synthesis.We also eliminated section 4 (reviewed about genetically modified E. coli), and merged it to section 3.

Point 3: The summarizing tables should be reinforced and, regarding the latter, the header titles of each table columns are confusing and not proper. Please, change them.

Response 3: We changed the header titles of each table to make it easier to understand.

Point 4: As personal opinion, the section 4: ‘Metal nanoparticle synthesis by genetically modified bacteria’ does not enter into the main scope of the review as it introduces a different and relevant topic worth of a much deeper analysis.  In turn, I would suggest analysing and describing better the issue related to the NPs purification together with their potential applicability especially in biomedical application (e.g. the presence of endotoxins, cell debrises, etc etc)

Response 4: As mentioned above, we eliminated section 4, and merged it to section 3. We created new section 4 “Purification of NPs synthesized by microorganisms”. In this section, we reviewed the methods of isolation nanoparticles synthesized by microorganisms and the application of purified NPs.

Point 5: Figure 3 is most proper of Introduction than Conclusions. Please, move it.

Response 5: We moved the figure3 and figure 4 to introduction section as figure 2 and figure 3.

Round 2

Reviewer 3 Report

The authors have addressed all the issues. The manuscript is now suitable to be accepted for publication.