Kinetics of Arab Light Crude Oil Degradation by Pseudomonas and Bacillus Strains
Round 1
Reviewer 1 Report
General: This manuscript entitled on “Kinetics of Arab Light crude oil degradation by Pseudomonas and Bacillus strains” provides a general viewpoint for hydrocarbons degradation rates by bacteria. Authors presented a great effort to prepare this manuscript, however, the reviewer has some queries about this paper. I would strongly suggest to check this manuscript by English experts. There is no set for ‘control’ experiment. Authors should have prepared at least one control set with only crude oil in MSM without containing any bacterial strain. The experimental data obtained from microbial degradation must be compared with control data which strengthen the reliability of the research. Also, all experiments must be done with at least 3 replicates for data repeatability. I ca see the authors only did one replicate for each experiment. This is the main fault of this paper. Please explain. I suggest that this manuscript can be acceptable with major revision. Other comments are as follows;
- The English language of this manuscript has several grammatical errors and it must be checked and corrected by native English experts.
- The abstract should be improved by including more numerical data.
- Line 8-9: Please revise the first sentence to be understandable for readers. Similar in Line 38-40. What is the consequence of what? Please explain.
- Line 15: Did the authors used chloromethane for extraction? Or they used dichloromethane (DCM)? This is not explained in Methodologies section.
- Line 20: What does the first order kinetic coefficient means? Is this value unitless? The first order rate constant should have a unit of time-1.
- There is lack of extensive literature review in this paper. Authors need to improve introduction section by citing several published literatures. For e.g., I could not see any citing references in the first paragraph (line 29-37), which contains several information. Revise the entire introduction section.
- I would suggest the authors to do an extensive literature review (cited) and improve the introduction section.
- Line 40-44: Please make this sentence simpler to be easily understandable for readers.
- The flow of writing in ascending paragraphs in the introduction should be connected with each other. What are the limitations of previous studies and why this study is important? Also, the specific objectives should be more intensified according to the research gaps in this field. It should be clarified by the authors.
- Line 113, 119: AGILENT ----à Agilent
- Line 141: Authors stated that they measured oil concentration several time as week by GC. But it is not specified that how many times a week they measured. Please revise with exact sampling time. In the scientific researches/experiments, everything must be clear about the experimental plans and procedures that have done and sampling time is the most important in research.
- I would like to know about volume of sample during sampling (in MSM) and its processing (extraction with some solvents) for crude oil characterization or measurements by GC-MS or GC-FID. Also, there should be internal standard added during extraction or processing of samples and standard solution. Explain.
- Section 3.1 (Crude oil characterization) and 3.2 (Sample analysis) with Figure 3 should be moved to section 2 (Materials and methods) or supporting information.
- Figure 3: Xilene -----à xylene. Xylene is the correct English word for this chemical. Also, mention which xylene is present in this oil. How did authors calculate the % weight or individual abundance for the composition of aliphatic hydrocarbons? Please explain how the percentage of C7-C12 compounds over aliphatic alkanes distribution is 46.4%.
- In Fig. 3 (upper, for standard solution), they mentioned chromatogram for C7-C30, however one can see only up to C29. It would be better if there is C30 peak.
- I wonder why authors do not marked above all peaks (corresponding n-alkane with C number) in all Figures?
- Figures 5 and 6 do not represent the actual kinetics of Arab Light degradation. They are only representative chromatogram. Kinetics should be evaluated in concentration or other data regarding rates or rate constants. Please revise.
- Line 311-316: Authors shown that low molecular alkanes are less degraded while medium chain alkanes were completely degraded within 5 weeks. In contrast, Bajagain et al. (2018, 2020) argued that mid-chain hydrocarbons are less readily biodegraded in soil than low molecular hydrocarbons. See the following literatures (and also other papers) and discuss them in the present paper;
1) Feasibility of oxidation-biodegradation serial foam spraying for total petroleum hydrocarbon removal without soil disturbance. Science of the Total Environment 626, 2018, 1236-1242. https://doi.org/10.1016/j.scitotenv.2018.01.212
2) Biodegradation and post-oxidation of fuel-weathered field soil. Science of The Total Environment 734, 2020, 139452. https://doi.org/10.1016/j.scitotenv.2020.139452
- Figure 7: Please describe about the characterization method for bacterial microphotographs in M&M section.
- Equation 1 to 6: There are no nomenclatures of different variables or constants (e.g. S, S0, r, k, t). Please define all the terms with their units after writing the equations, not in the Nomenclature section. Also, where do Eqs 1 and 2 arise from? Please explain.
- Line 414: It seems that the authors calculated degradation rates using equation 7 and 8 as they obtained degradation rates of 843 mg/Ld and 705 mg/Ld using SoArabLight = 8.6 g/L. However, the Equations have the term ‘S’, not the ‘S0’. I am confused why authors used different equations? Is the terms ‘S’ and ‘S0’ have same meaning or ‘S’ is the concentration at time t? Authors must respond it.
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Reviewer 2 Report
This work is more like a case study. I can't see enough scientific problems in it.
Author Response
English language has been revised in the new version of the manuscript.
Thanks for your contribution.
Reviewer 3 Report
Manuscript ID: water-1965992
Title: Kinetics of Arab Light crude oil degradation by Pseudomonas and Bacillus strains
The investigation was on the kinetic study of the microbial degradation of Arab light crude oil.
The manuscript cannot be recommended in its current form. Authors are advised to do the needful based on the comments below.
-Write the symbols of the hydrocarbon in the generally accepted way. For example, using C28 instead of C28 is not scientifically current. There are many of such instances in the manuscript
-what is the unit of the rate constants as provided in the abstract----line 20
-there should be at least two references inserted into lines 28 to 37, especially lines 36 to 37. Note that it is not appropriate to write close to 10 lines of statement without adequate reference (s)
-maintain a single space between a value and the unit. Please correct this in the body of your text
-recast the sentence from ‘’when crude oil …………to be adjusted. It is not explanatory enough
-The models/or equations and steps for the kinetic study should be appropriately provided under materials and methods rather than under the results and discussion section. Equations 1 to 6 should be moved to material and methods with the adequate explanation provided. For example, what are the kinetic parameters in the equations, their definitions, and their significance to crude oil degradation? You need to define the parameters k, t, S, and So
-Let the reader know more about how equations 7 and 8 were arrived at.
-provide the equation that made the degradation rate, r, to be estimated. How was this parameter estimated? Which equation did you use to estimate this.
-lines 410-412. what made the authors to conclude that B. licheniformis exhibits higher potential for crude oil degradation than P. putida? What has the value obtained got to do with the actions of the microbes? A clearer explanation must be provided
-the title of this work is focussed on the kinetics of degradation of crude oil,however, this part was not comprehensive enough. Kindly improve more on section 3.4
-explain how the degradation rates of 843 mg/Ld and 705 mg/Ld were arrived at, and why 30 oC?
-explain further according to the statement in line 416-417 how the obtained kinetic parameters can be used to project bioreactor size and time range in biodegradation assay
RECOMMENDATION
MAJOR REVISION
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
They have responded and revised most of the comments made by the reviewer. Authors should have highlighted all the changes that they have made in the revised manuscript, so that reviewer can easily find the changes made by them. But they have not highlighted some revised contents (e.g., in abstract, added references and sentences after citing some literatures in the main text).
I would suggest the revised version of this manuscript can be accepted for the publication.
Author Response
Sorry for contents which are not highlighted in the last version of the manuscript, I think this was an error in using the "Track Changes" function of MSWord.
Thank you so much for your efforts in improving this manuscript.
Reviewer 2 Report
The authors have made some modifications of this article and this version is better than last one. However, there is still some minor issues should be addressed before publication. The introduction is not enough and more literature should be included. For example, the role of transparent exopolymer particles (TEP) in membrane fouling: A critical review; Transparent exopolymer particles (TEPs)-associated protobiofilm: A neglected contributor to biofouling during membrane filtration.
Author Response
These comments are not referred to our article. I think this is an error and this report was done for another paper.
Thank you anyway.
In the first Review Report (Round 1), no instructions were indicated by the reviewer. We interpret there are no instructions for this Round 2.
Thank you for your contribution.
Reviewer 3 Report
Comments from the reviewer have been adequately attended to
Author Response
Spelling of English words and sentences has been revised.
Thank you very much for helping to improve the manuscript.
