Self-Sustaining Bioelectrochemical Cell from Fungal Degradation of Lignin-Rich Agrowaste

Round 1

Reviewer 1 Report

The authors have communicated the microbial fuel cell operated with microbial zinc anode and air cathode using white-rot fungus of Phanaerochaete chrysosporium and oil palm empty fruit bunch (EFB) as the substrate. This piece of work is interesting to me and it can be communicated after the following minor revisions.

Page 167-169: “Thus, the resulting discharge capacity of 1056 mAh is the highest recorded by a bio catalyzed, single electrochemical cell, to the best of our literature survey.” I would suggest adding the relevant literature to justify this discharging capacity. For example, a bad wine-fed microbial fuel cell continuously produced a sustainable operating voltage of 0.535 V with a current output of 0.89 mA. Hence the power output will be 470 ± 5 μW. This power will be 500 times higher than the power required to run a wall clock which requires only 8–10 μW at a minimum voltage of 1.3 ± 0.2 V (Bioresource technology, 104 (2012) 388-393.)

Page 5-6: In figure 2-4, the curve legends should be identified as abiotic control cell and biofuel cell respectively.

Page 158-159: “The MFC registered a stable open-circuit voltage of around 1.2 V. “Most” MFCs are characterized under constant load discharge, typically 1000 Ω.” I would suggest including the citations of the relevant paper for discharge the biofuel cell at constant load (eg., Environmental Science & Technology, 43 (2009) 8684-8689)

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors, 

Thank you for submitting your work to Energies. Overall quality of this paper is good, but two things should be improved before publishing.

1) Expand the literature review with details, such as the capacity / current density and durability/life cycle data from other researches. Please give some comparisons between your work and others to enhance the importance of your work. 

2)  Brief analyze your data from Figure 2 and Figure 3 from the point of electrochemistry view, such as the activation loss, ohmic loss, mass transport loss, crossover/short-circuit possibility. 

Thank you. 

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.docx

Reviewer 3 Report

Minor Revision

energies-1140439-peer-review-v1

The submitted article “energies-1140439” describes a self-sustaining bio-electrochemical system that adopts simple cell configurations and operates in uncontrolled ambient environments. The author mentioned the capability of the MFC to sustain its release under extended extent despite the fungal microbes not attached to the air electrode is attributed to the network of filamentous hyphae formation under the submerged culture. Apart from that, however, there is points need for clear clarifications and more explanations, and thus a minor revision is required.

Comments are as follows:

Reviewer comments

1. In the introduction section, the authors mentioned carbon nanotubes (CNT). In my opinion, the author needs to compare other carbon-based materials as support materials and compare their efficiency in MFC.

Please see the given reference which is related to the MFC and carbon-based materials and cite them in the appropriate section.

doi.org/10.1016/J.BIOS.2006.01.030

doi.org/10.1038/s41598-018-19617-2

doi.org/10.1039/C8RA00690C 

2. Is it possible for the fungal microbes cultured on-air cathode as a current collector?
3. As the author mentioned, “10 days, the rugged lignin external surface had been smoothened and thinned resulting from the metabolic activities of the fungal microbes” is this the optimal time for the metabolic activities of fungal microbes?
4. The author needs to provide a clear scale in figure 6 (Optical microscopic images).
5. The author needs to check English throughout the text, typos error, and spacing between words.
6. All references must be on the pattern of the journal guidelines, consider all the commas, full stops, etc,
7. Overall, the writing and included information seem reasonable except for the above-mentioned comments, the author needs to include all the suggestions and cite the given articles before acceptance.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.docx