Biosorption and Bioleaching of Heavy Metals from Electronic Waste Varied with Microbial Genera

Round 1

Reviewer 1 Report

In this article, seven mcrobial cultures for the biosorption and bioleaching of metals from PCBs had been studied. It was found that there existed the highest capability of Pleurotus florida and Pseudomonas sp. for biosorption and bioleaching of copper and iron. It was proved that the laccase activity could be induced by copper to improve the ability of bioleaching in this article. The P. florida and Pseudomonas sp. have potential to bioleach and biosorption of metals from E-waste. The innovation of this article is that laccase activity was proposed as an evaluation index of bioleaching, and SDS-PAGE was used to characterize the protein induced by copper. This paper could be accepted after some revisions which listed as following,

1. The title “Screening of microorganisms for e-waste remediation”on line 116 has no number.
2. B.The Figure 1 has no marks (a,b,c,d).
3. C. Some tables should be made into figures.

Author Response

Dear Reviewer,

We sincerely thank you for your comments and suggestions.

The point-wise reply is appended below:-

Summary: In this article, seven microbial cultures for the biosorption and bioleaching of metals from PCBs had been studied. It was found that there existed the highest capability of Pleurotus florida and Pseudomonas sp. for biosorption and bioleaching of copper and iron. It was proved that the laccase activity could be induced by copper to improve the ability of bioleaching in this article. The P. florida and Pseudomonas sp. have potential to bioleach and biosorption of metals from E-waste. The innovation of this article is that laccase activity was proposed as an evaluation index of bioleaching, and SDS-PAGE was used to characterize the protein induced by copper. This paper could be accepted after some revisions.

Reply: We sincerely thank you for your positive comments on the study. We will put best efforts to modify the content of the manuscript as indicated by you.

Comment 1: The title “Screening of microorganisms for e-waste remediation” on line 116 has no number.

Reply: The number has been given to the title as indicated by the reviewer.

 

Comment 2: The Figure 1 has no marks (a,b,c,d).

Reply: A revised figure has been incorporated in the manuscript with marks.

 

Comment 3: Some tables should be made into figures.

Reply: Table 2 has been changed to line graph for better depiction of the changes in the laccase activity in a time-lapse manner.

Reviewer 2 Report

please consider E-waste throughout the paper

specify the type of equipment used for analytical measurements (Manufacturer, City, Country).

row 37: between 10.5%-18.0%.Protein characterization – consider revising to: between 10.5%-18.0%. Protein characterization

row 111: 48h to remove – consider revising to: 48 h to remove

row 143: 8^thday – consider revising to: 8^th day

row 144: 20^thday – consider revising to: 20^th day

row 148: in3:1ratio - consider revising to: in 3:1 ratio

row 244: Table 4.Therefore – consider revising to: Table 4. Therefore

row 320: Shah et al[23]. – consider revising to: Shah et al [23].

Author Response

Dear Reviewer,

Sincere thanks for your constructive comments and suggestions.The point-wise reply to each comment is given below:-

Comment 1: Please consider E-waste throughout the paper.

Reply: The word e-waste’ has been replaced with ‘E-waste’ throughout the revised manuscript.

Comment 2: specify the type of equipment used for analytical measurements (Manufacturer, City, Country).

Reply: The information pertaining to equipment has been updated in the revised manuscript.

Comment 3: row 37: between 10.5%-18.0%. Protein characterization – consider revising to: between 10.5%-18.0%. Protein characterization

Reply: The indicated change has been incorporated in the revised version of the manuscript.

Comment 4: row 111: 48h to remove – consider revising to: 48 h to remove

Reply: The indicated change has been incorporated in the revised version of the manuscript.

Comment 5: row 143: 8^thday – consider revising to: 8^th day

Reply: The indicated change has been incorporated in the revised version of the manuscript.

Comment 6: row 144: 20^thday – consider revising to: 20^th day

Reply: The indicated change has been incorporated in the revised version of the manuscript.

Comment 7: row 148: in3:1ratio - consider revising to: in 3:1 ratio

Reply: The indicated change has been incorporated in the revised version of the manuscript.

Comment 8: row 244: Table 4.Therefore – consider revising to: Table 4. Therefore

Reply: The indicated change has been incorporated in the revised version of the manuscript.

Comment 9: row 320: Shah et al[23]. – consider revising to: Shah et al [23].

Reply: The indicated change has been incorporated in the revised version of the manuscript.

best regards

 

Reviewer 3 Report

Summary

This article evaluates biosorption and bioleaching potential of seven microbial cultures using printed circuit board (PCB) as substrate under submerged culture conditions, while screening certain microbial cultures via the Atomic absorption spectroscopy (AAS) analysis, SEM-Energy-dispersive X-ray spectroscopy (EDS) and Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The study reveals Pleurotus flor-ida and Pseudomonas spp. can be considered as a potential candidate for the biosorption of metals from electronic waste as an eco-friendly and economical process.

 

Specific comments

• Introduction

1. Line 80-85, page 2: Please specify outcomes of “these studies” to strengthen the scientific view of the study.
2. Line 102, page 3: The statement of “a more efficient remediation” lacks evidentiary support. The authors should compare this approach with prior studies.

 

• Material and methods

1. Line 142, page 3: The error occurs in word selection. The phrase “studies” brings readers a feeling: The section was about literature review, rather than the steps of the experiment. Similar use happens in Line 158, 173, 195, 210, 222, 230, 252, etc.
2. Line 195, page 4: Suggest to delete the conjunction – however since there was no transition relation.

 

• Results

1. Line 200-202, page 5: Only two reported studies cannot support that results from the metal content analysis of the present study fluctuated among the reasonable range. Please verify the value via authoritative reports.
2. Line 218-220, page 5-6: Suggest shifting Table 2 into the line chart as the upper descriptions mainly concentrate on the trend analysis, and the line chart can reflect the trend well.
3. Line 280, page 8: Please verify the name-SEM-EDS. It is not tally with the name-SEM-EDX.
4. Line 294-296, page 8: Panels in Figure 2 are not explicit. Please shift it into a clearer one.
5. Figure 3 is unclear.

 

• Discussion

1. Throughout the whole discussion section, the authors have enumerated previous studies to discuss, such as in Line 330, 334, 337, 348, 370, 377, 384, 412, 442, etc. Discussing many other studies’ results may lead to less focus on own study’s results so that the section has deviated from the key points. Note that in the desorption section of the discussion, the authors have not discussed their results. In the interest of applications, the authors should discuss if the recovery efficiency is higher than other microbe products and attractive on the market and so on.
2. Line 473, page 12: Please tally this in-text citation style with others.

 

• Conclusions

1. In dissertations and research papers, conclusions tend to be more complex and will also include sections on the significance of the findings. Unfortunately, this study did not demonstrate any significance of the study, limitations and recommendations.

 

• References

1. The list of references should be blocked into separate pages.

 

Recommendation

The authors should do a major revision. First and foremost, there is a lack of scientific added-value explanations in this manuscript as a series of comparisons among previous studies are not based on scientific insights. Thereafter, the organization of the paper is irrational. Previous studies’ results are supposed to be displayed in a literature review section, rather than interspersing in the discussion. Last but not the least, there is a lack of discussion on the novelty of this study. The authors did not provide past relevant studies to highlight the research gap (refer to the introduction, line 102); in the conclusion part, the authors did not provide any limitations and recommendations either.

Author Response

Dear Reviewer,

We are very thankful for your insights and constructive comments which have helped a lot to improve the contents of this manuscript. The reply to your comments is appended below:-

Reviewer 3:

Specific comments

Comment 1: Introduction

Comment 1.1: Line 80-85, page 2: Please specify outcomes of “these studies” to strengthen the scientific view of the study.

Reply: The final outcome of few studies has been incorporated in the revised version of the manuscript to strengthen the scientific viewpoint of this study.

 

Comment 1.2: Line 102, page 3: The statement of “a more efficient remediation” lacks evidentiary support. The authors should compare this approach with prior studies.

Reply: New supplementary tables (ST1 and 2) have been incorporated to provide the necessary evidence required to prove the environment-prudence and cost-effectiveness of this approach over the existing conventional approaches.

 

Comment 2: Material and methods

 

Comment 2.1: Line 142, page 3: The error occurs in word selection. The phrase “studies” brings readers a feeling: The section was about literature review, rather than the steps of the experiment. Similar use happens in Line 158, 173, 195, 210, 222, 230, 252, etc.

Reply: The indicated change has been incorporated in the revised manuscript.

 

Comment 2.2: Line 195, page 4: Suggest to delete the conjunction – however since there was no transition relation.

Reply: The suggested change has been incorporated.

 

Comment 3: Results

Comment 3.1: Line 200-202, page 5: Only two reported studies cannot support that results from the metal content analysis of the present study fluctuated among the reasonable range. Please verify the value via authoritative reports.

Reply: New studies have been incorporated in the table 1 to substantiate the range of metal content in the PCB samples.

 

Comment 3.2: Line 218-220, page 5-6: Suggest shifting Table 2 into the line chart as the upper descriptions mainly concentrate on the trend analysis, and the line chart can reflect the trend well.

Reply: The Table 2 has been converted as line graph (Figure 1) in the revised manuscript.

 

Comment 3.3: Line 280, page 8: Please verify the name-SEM-EDS. It is not tally with the name-SEM-EDX.

Reply: The term SEM-EDS has been changed to SEM-EDX throughout the manuscript.

 

Comment 3.4: Line 294-296, page 8: Panels in Figure 2 are not explicit. Please shift it into a clearer one.

Reply: A revised figure (Figure 3) has been inserted in the manuscript.

 

Comment 3.5: Figure 3 is unclear.

Reply: The SDS-PAGE image has been replaced with high resolution image as Figure 4.

 

Comment 4: Discussion

Comment 4.1: Throughout the whole discussion section, the authors have enumerated previous studies to discuss, such as in Line 330, 334, 337, 348, 370, 377, 384, 412, 442, etc. Discussing many other studies’ results may lead to less focus on own study’s results so that the section has deviated from the key points. Note that in the desorption section of the discussion, the authors have not discussed their results. In the interest of applications, the authors should discuss if the recovery efficiency is higher than other microbe products and attractive on the market and so on.

Reply: The discussion section has been modified in light of the comments of the learned reviewer.

 

Comment 4.2: Line 473, page 12: Please tally this in-text citation style with others.

Reply: The indicated reference has been formatted as per the journal guidelines.

 

Comment 5: Conclusions

Comment 5.1: In dissertations and research papers, conclusions tend to be more complex and will also include sections on the significance of the findings. Unfortunately, this study did not demonstrate any significance of the study, limitations and recommendations.

Reply: The conclusion section has been thoroughly modified to include the final take of the study.

 

Comment 6: References

Comment 6.1: The list of references should be blocked into separate pages.

Reply: The references have been shifted to new page.

 

Recommendation

The authors should do a major revision. First and foremost, there is a lack of scientific added-value explanations in this manuscript as a series of comparisons among previous studies are not based on scientific insights. Thereafter, the organization of the paper is irrational. Previous studies’ results are supposed to be displayed in a literature review section, rather than interspersing in the discussion. Last but not the least, there is a lack of discussion on the novelty of this study. The authors did not provide past relevant studies to highlight the research gap (refer to the introduction, line 102); in the conclusion part, the authors did not provide any limitations and recommendations either.

Reply: We thank you for your critical comments that have been very useful for improving the contents of this manuscript. The explanations have been improved to improve the rational and organization of the contents. The content in discussion has been removed and modified to improve the coherence and flow of the contents. The conclusion has been changed to include the limitations and recommendations. We hope you will find the revised version more correct and will approve it. Sincere thanks for your constructive comments.

 

Round 2

Reviewer 3 Report

The comments have been responded to accordingly and it is fit for publication.