Biohydrogen Production under Aerial Conditions by a Nitrogen-Fixing Bacterium Isolated from a Steel Signboard

Round 1

Reviewer 1 Report

In this paper, a new bacterium Cereibacter sp. KGU-NF001 was isolated to produce hydrogen in under aerial conditions. Cereibacter sp. KGU-NF001 showed promising oxygen tolerance and was able to maintain hydrogen production of 1.33 mL mg−1 d−1 even when the atmosphere contained 12% oxygen. These are interesting. However, the manuscript should be undergone major revisions before being accepted. Suggestions are as follows.

1) The morphology of the Cereibacter sp. KGU-NF001 should be shown.

2) The pictures of the filter membranes with the bacterial strains and placing the membranes on medium-soaked cotton wool should be given.

3) How the hydrogen is collected should be given and the hydrogen purity should be evaluated.

4) The light conditions (radiation area, light intensity and light wavelength) should be given.

5) Does the hydrogen production process of photosynthetic bacteria need to supplement water and nutrients, and how to supplement, that is, how to maintain the continuous hydrogen production of the Cereibacter sp. KGU-NF001.

6) In the Introduction and Discussion sections, some important paper can be referenced to enhance the readability of the manuscript, such as 1) Current challenges and future technology in photofermentation-driven biohydrogen production by utilizing algae and bacteria; 2) A fiber-optic sensor for accurately monitoring biofilm growth in a hydrogen production photobioreactor; 3) Enhancement of hydrogen production by optimization of biofilm growth in a photobioreactor; and so on. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

General comments

·                  In overall, I found the work very interesting and in line with the Journal scope. Presentation and writing style is good with some lapses in style. Structure is clear.

·                  Title: appropriate

·                  Abstract: it well written and main data results are presented.

·                  Methodology: Good description, coherent and detailed.

·                  Analysis and discussion: Data in the Figures could be corrected in order to be more readable.

·                  References: >75% οf References are up-to-date.

Specific comments (list not exhaustive)

Introduction:

If possible, to add more information regarding the aim of this study

Materials and Methods:

L121: there was a differentiation of O2 concentration into the headspace of the test tubes? Please clarify.

L145: Please give an example instead of writing XXxxxxxx

Results and Discussion:

Fig2: Liquid phase (N2; Light grey) should be darker. The statistically significant differences (p<0.05) could be indicated as single asterisk (and not as a bar); Same comment for Fig3

L167: Please correct Figure 2b (instead of Figure 2B) ; Same comment for Fig3; L197, L213, L220 and all through the manuscript

L179: Correct “Because” with “Due to the fact that”

A general comment: Why choosing Ar as inert gas instead of He?

Fig5: Could you replace solid black circles with solid triangles?

On the basis of the above, my recommendation is a Minor revision and I hope the authors define my perspective useful in improving their manuscript.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

All the comments have been resolved. The revised manuscript shoulf be accepted.