Isolation of Biosurfactant-Producing Bacteria and Their Co-Culture Application in Microbial Fuel Cell for Simultaneous Hydrocarbon Degradation and Power Generation
, Soumya Pandit 1,*, Bhim Sen Thapa 3, Kumud Pant 4 and Tanmoy Roy Tusher 3,5,*
Round 1
Reviewer 1 Report
In this submission, the authors have reported the isolation of two biosurfactant-producing bacteria and their application for MFC-based hydrocarbon degradation. These two bacteria show synergism in the co-culture system for enhanced power generation and hydrocarbon breakup. The topic is interesting and could attract wide readership from scientists in the area of sustainability. Therefore, I recommend its publication after the following issues are addressed.
1. The FTIR peaks at 3398 and 3417 cm-1 are very close. Please make sure that the peak at 3417 cm-1 is ascribed to hydrocarbon chain of alkyl. Please also add references to support this description.
2. Please add the equivalent circuit for simulation. Why the Rs increases when the concentration of crude oil increases from 2.5% to 3%?
3. The widths of lines in Fig. 1 and Fig. 3 should be increased.
4. There are some grammatical errors in the text. For example, “use” (line 79) should be “used”; “breakdown” (line 90) should be “break down”; “It has shown” (line 584) should be “It has been shown”.
5. The authors are recommended to cite relevant references for description of background and understanding of characterization and electrochemical measurement data such as Colloids Surf. A Physicochem. Eng. Asp. 2013, 439, 69–83; J. Mater. Chem. A 2015, 3, 1961–1971; Adv. Funct. Mater. 2012, 22, 1932–1939.
Comments for author File: 
Comments.pdf
Author Response
Reviewer’s comments
First, the authors would like to thank all reviewers for their valuable suggestions and corrections in enhancing our manuscript. Apart from those, the authors have included a few relevant points to improve the quality of the manuscript.
Reviewer #1
- The FTIR peaks at 3398 and 3417 cm-1are very close. Please make sure that the peak at 3417 cm-1 is ascribed to the hydrocarbon chain of alkyl. Please also add references to support this description.
Response: The FTIR peak at 3398 and 3417 cm-1 denotes the presence of a hydroxyl group for both cases [1,2][Reference 62]. The error has been removed, and the reference has been added to support the description (line 441-444, Page no. 12). Changes have been made as per the reviewer’s comment (annotated version).
- Please add the equivalent circuit for simulation. Why does the Rs increase when the concentration of crude oil increases from 2.5% to 3%?
Response: As per the reviewer's suggestion, an equivalent circuit has been added and numbered as figure 8 (line 514-527, Page no. 16). Due to crude oil's non-conductivity and hydrophobic nature, the solution resistance increases dramatically. Changes have been made as per the reviewer’s comment.(annotated version)
The following sentences has been included after figure 8 :
“…. Electrochemical impedance spectroscopy (EIS) was employed to estimate the different internal resistances of MFC. The Nyquist plot consisted of a semicircle and a linear portion, which represents charge-transfer resistance and diffusion resistance respectively. This implies that the electrochemical reaction on the biofilm is mix-controlled by charge transfer and diffusion step. The experimental spectra were fit into equivalent circuit to evaluate the impedance data.(Lines 522-527)”.
- The widths of lines in Fig. 1 and Fig. 3 should be increased.
Response: As suggested by the reviewer, The width of lines Fig. 1 and Fig. 3 has been increased (Lines 349-352, Page no.-8 and 376-377, Page no. 10). Changes are made as per the reviewer’s recommendation (annotated version)
- There are some grammatical errors in the text. For example, “use” (line 79) should be “used”; “breakdown” (line 90) should be “break down”; “It has shown” (line 584) should be “It has been shown”.
Response: As suggested by the reviewer, grammatical error in the text has been rectified (lines 78, 89 and 593). Changes were made as per the reviewer’s recommendation. (annotated version).
- The authors are recommended to cite relevant references for the description of background and understanding of characterization and electrochemical measurement data such as Colloids Surf. A Physicochem. Eng. Asp. 2013, 439, 69–83; J. Mater. Chem. A 2015, 3, 1961–1971; Adv. Funct. Mater. 2012, 22, 1932–1939.
Response: As suggested by the reviewer, relevant references for a description of the background and understanding of characterization and electrochemical measurement data have been included (references 48, 53 anf 59 of the annotated version). Changes were made as per the reviewer’s recommendation. (annotated version).
Reviewer 2 Report
The isolation of biosurfactant-producing bacteria and their co-culture application in MFC for simultaneous hydrocarbon degradation and power generation is shown in this work.
The work reports the isolation of biosurfactant-producing bacteria that can be used for crude oil remediation and also reports on evaluating the synergism and potentiality of biosurfactant-producing bacteria for simultaneous hydrocarbon biodegradation and power generation.
It has been shown that the co-culture of isolated crude oil-degrading strains has a great potential for enhanced power generation and bioremediation of hydrocarbon-contaminated environments, and that the synergism of isolated strains in MFCs suggested their applicability in environmental engineering as an alternative to the existing technologies. This alternative is admittedly not a technology for the coming years. However, research in this area is extremely important as a technology of the future, where wastewater can be treated as a green source of energy.
Therefore, conducting research in the field of increasing the efficiency of MFCs is extremely important. The more that this technology is developing at an ever faster and faster.
The measurements has been shown that by co-culture of isolated strains (1:1 ratio) in the MFC were obtained the power density of 6.3 W/m3 with an open circuit voltage of 370 mV. Therefore, combined application of analysed strains can be utilized to enhance power production as well as clean-up hydro-carbon-contamination owing to their synergism in the co-culture system.
References items have been well chosen.
Some suggestion follows:
- it should be good to improove the abstract,
- it should be good to analyze or rewrite the conclusions,
- it must be increase the resolution and quality of some figures, e.g. Figure 7, Figure 8 - to make the figures easier to read
Author Response
Reviewer’s comments
First, the authors would like to thank all reviewers for their valuable suggestions and corrections in enhancing our manuscript. Apart from those, the authors have included a few relevant points to improve the quality of the manuscript.
Reviewer #2
- It should be good to improve the abstract.
Response: As the reviewer suggested, Some unnecessary lines have been removed and some additional information has been added in the abstract, author already has been summarized full manuscript (Lines 21-23, and 32 and 34 Page - 1). Changes are made as per the reviewer’s recommendation. (annotated version)
- It should be good to analyze or rewrite the conclusions.
Response: As the reviewer suggested, the conclusion has been updated (Lines 581-599, Page-18). Changes are made as per the reviewer’s recommendation. (annotated version)
- It must increase the resolution and quality of some figures, e.g. Figure 7, Figure 8 - to make the figures easier to read
Response: Thank you for the comment; as the reviewer suggested, Figure 7 and figure 8 have been updated in high resolution (Lines 496- 499 , Page no.- 15 and 538-540, Page no.-17). Changes have been made as per the reviewer’s comment. (annotated version)
