Construction and Degradation Performance Study of Polycyclic Aromatic Hydrocarbons (PAHs) Degrading Bacterium Consortium

Round 1

Reviewer 1 Report

General opinion

It has long been known that bacteria and especially their consortium degrade PAH.

It is necessary to clearly write what new facts this study has established.

What is the applied value of research?

Maybe you can recommend creating a biological tool for bioremediation based on the studied strains? In this case, it is necessary to indicate what advantages the strains and their consortium studied in this investigation have.

Line 34

In the introduction it is necessary to write more about the sludge. What types of sludge are there? What is the sludge usually contaminated with, what microorganisms usually live in it? Explain why you need to look for PAH destructors in sludge.

Line 78-80

More detailed characterization is needed for the sludge used in this experiment. Bring the concentration of PAHs in the sludge in this section, clarify what other components are included in the sludge’s composition. What is the oil content of the sludge? What types of petroleum products does oil consist of? Data about PAHs are partly presented in the Results and Discussion section. Rather, it refers to the characteristics of the object. It is also necessary to decipher the abbreviations NAP, PHE, PYR.

Line 91

«Streak plate method» would be more correct

Line 91

The information from section 3.1 should be transferred here.

About the taxonomic affiliation of bacteria. Please note that it is necessary to identify bacteria based on the 16S ribosomal DNA sequence and upload this information to NCBI.

Line 57, 93, etc

Purebred? What does it mean? Probably, you means "pure bacterial culture". So it should be written, including further everywhere in the text

Line 110.

Question for the determination of PAH residues by UV-vis spectrophotometer. Provide references where this method was used. Add the spectra you obtained to additional materials. What absorption maximum were used for the PAHs? What was used as a reference? Did the components of the medium and bacterial metabolites interfere with the determination of PAHs?

Line 128

What is the point of studying resistance to metals in the framework of this investigation? Is the sludge contaminated with heavy metals? If so, in what and in what concentrations?

Line 148-149.

What is the volume of inoculum? What is the optical density of the culture immediately after inoculation? What was the optical density at the end of cultivation?

Line 156-157. Transfer information about bacteria to the section Experimental methods and materials. Carry out identification as described above.

Line 165, 169, 192, 213, etc.

Naphthalene is a volatile compound. How was volatilization taken into account when assessing the rate of NAP degradation? What control variants were used in experimental design?

Line 192.

What does it mean «were used as a reference?»

Line 201. Reformulate

Line 208-209. How does the ratio of different strains change during the experiment? What is it at the end? And in the sludge, what is the ratio?

Line 265 Strains? May be cells?

Line 273

What fractions does crude oil consist of? What is the proportion of volatile components? Was there a control without bacteria?

 

Line 339

If there is data on the destruction of oil in the sludge during the experiment, it is also worth add.

Line 352.

 In conclusion, it is necessary to clearly state which data were obtained for the first time and what practical significance it has.

Comments for author File: Comments.docx

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers comments concerning our manuscript entitled “Construction and degradation performance of Polycyclic aromatic hydrocarbons degrading bacterial consortium in oily sludge”. (ID: applsci-1554972 ). Please see the attachment for the reply

I wish you all the best!

Sincerely,

Bo Yang

Email: [email protected]

Author Response File: Author Response.docx

Reviewer 2 Report

Comments to authors:

The authors submitted the manuscript entitled "Construction and degradation performance study of polycyclic aromatic hydrocarbons(PAHs) degrading bacterium consortium" with a number of 1554972to be able to publish at Applied Sciences.

Honestly, the manuscript needs to be revised and improved in order to be able for publication consideration. So that I cannot recommend the publication of the manuscript in its actual state. A major revision is recommended.

Some comments are below:

• The authors should mention all chemicals used in the work with supplies details.
• The authors failed to explain their work clearly and presented the importance of their work. So, the manuscript should be scientifically revised.
• The manuscript in the present form is so difficult for readers to be understood.

Comments for author File: Comments.pdf

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers comments concerning our manuscript entitled “Construction and degradation performance of Polycyclic aromatic hydrocarbons degrading bacterial consortium in oily sludge”. (ID: applsci-1554972 ). Please see the attachment for the reply

I wish you all the best!

Sincerely,

Bo Yang

Email: [email protected]

Author Response File: Author Response.docx

Reviewer 3 Report

The article „Construction and degradation performance study of polycyclic aromatic hydrocarbons(PAHs) degrading bacterium consortium” submitted to Applied Sciences shows results of an interesting study on the formation of bacteria consortium from selected organisms capable of degrading PAHs. However, the manuscript is poorly written and needs numerous corrections including extensive editing to correct English grammar and style. The authors should take more care to clarify what they did and how the experiments were performed.

In the introduction section explain the abbreviation P&A in the text (page 2). It is described only in the abstract. It is also better to write a few times P&A consortium instead of only P&A throughout the entire manuscript.

In section 2.2.2 describe the GC column that was used. Also, give the split ratio (e.g. 1:10).

In section 2.2.4 write what was used as a standard.

In section 2.2.6 write what MIC abbreviation means.

In Table 1 correct the name Alcaligenes faecalis – there’s a missing space.

In section 3.2.1.1 (line 181) correct the order of strains. According to the text, Alcaligenes faecalis is 1-5 which is not true.

Section 3.3 (lines 234-236). It is not clearly written where the NAP concentration of 2000 mg/L was used. From what I understood it was used in the experiment presented in Fig. 5 a, b, d. Fig. 5 c shows different concentrations of PAHs. You should write a more precise description of Fig. 5 in its caption.

Section 3.3 (line 248) pH 4-7 was mentioned but there is only a 5-9 range in Fig. 5 b.

Section 3.3 Fig. 5 d. The results are interesting but how can you use these results (percentage of bacterial inoculum) in field studies?

Section 3.3 (lines 284-291) You write that short linear and branched alkanes from crude oil stimulate the growth of the P&A consortium leading to better removal of PAHs. However, PAHs are removed at the same level at all tested concentrations of crude oil. There is no influence of crude oil concentration on the removal of PAHs.

Section 3.3 (lines 291-296) You write that short chain alkanes from crude oil support growth of the P&A consortium that results in a good degradation of PAHs. According to you only at greater concentration of crude oil (10 g/L) degradation of asphaltene gum and other refractory substances is reduced. However, we may see in Fig. 6 that removal of crude oil is the lowest at 0.5 g/L. You have to re-think your conclusions in lines 291-296.

Section 3.4.3 (lines 337-338) You write that the same removal of PAHs is with and without Triton that is true. However, next, you write that there is no influence of surfactants on the degradation of PAHs that is not true – see tween-80, APG-1214. The degradation of PAHS clearly depends on the type of surfactant used. You may not write that there is no effect.

Fig. 10 The error bars are hardy visible (especially for PHE).

Section 4 (conclusions – lines 359-360) Again you write “there is no considerable effect of surfactants”. This is not true.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers comments concerning our manuscript entitled “Construction and degradation performance of Polycyclic aromatic hydrocarbons degrading bacterial consortium in oily sludge”. (ID: applsci-1554972 ). Please see the attachment for the reply

I wish you all the best!

Sincerely,

Bo Yang

Email: [email protected]

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Are there data on the effectiveness of bacterial consortia in other studies in similar objects? If yes, then it is necessary to clarify why the proposed consortium is more effective than the previously proposed ones. This information should be included in the conclusion.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers comments concerning our corrected manuscript entitled “Construction and degradation performance of Polycyclic aromatic hydrocarbons degrading bacterial consortium in oily sludge”. (ID: applsci-1554972 ). You can See the attachment for our reply. Thank you again for your suggestion.

I wish you all the best!

Sincerely,

Bo Yang

Author Response File: Author Response.docx

Reviewer 2 Report

Authors answer all comments in reasonable way and modified the manuscript as per suggested. So, I recommend the acceptance of the manuscript as it is.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers comments concerning our corrected manuscript entitled “Construction and degradation performance of Polycyclic aromatic hydrocarbons degrading bacterial consortium in oily sludge”. (ID: applsci-1554972 ). You can See the attachment for our reply. Thank you again for your suggestion.

I wish you all the best!

Sincerely,

Bo Yang

Author Response File: Author Response.docx

Reviewer 3 Report

I have read the corrected manuscript “Construction and degradation performance study of polycyclic aromatic hydrocarbons(PAHs) degrading bacterium consortium”. Although the idea of the study and presented results are interesting, there are still some corrections to be done.

Two main issues MUST be resolved.

1-ST – CORRECT ENGLISH – I CAN BARELY UNDERSTAND WHAT YOU MEAN.

The amendments made so far have made the article worse. Seek professional assistance.

2-ND – RETHINK THE DISCUSSION IN LINES 299-319 – SEE BELOW.

In lines 299-300 you write that “crued oil content factor would not impact NAP, PHE and PYR degradation”. This is true, but in lines 302-303 you write “The possible reason for the complete degradation of NAP, PHE and PYR caused by the addition of crude oil is that there were short linear and branched alkanes with simple structure in crude oil”. This is contradictory because there is no impact of crude oil on the removal of NAP, PHE and PYR. The degradation rate of these three compounds presented in Figure 6 is always almost 1.

In lines 308-310 you write “After the easily degradable short chain alkanes and straight chain alkanes were consumed, a large number of bacteria began to degrading the NAP, PHE and PYR, therefore, its degradation rate was greatly increased.” There is no difference in the degradation rate of NAP, PHE and PYR depending on crude oil content – see Figure 6.

In lines 317-319 you write “The intermediate products produced by NAP, PHE and PYR or asphaltene and gum are toxic to the P&A bacterial consortium, lead to the death of microorganism, and the crude oil degradation rate was also declined.” The initial concentration of NAP, PHE and PYR is constant. It cannot be more toxic to bacteria at 10 g/L crude oil than at 5 g/L. It looks rather like the products formed during the degradation of crude oil at 10 g/L may be toxic to bacteria. Also, to support this statement bacteria viability in these tests should be verified and compared. Otherwise, this is just speculation.

 

Also, based on the above text, in lines 397-398 you write “The additional crude oil could further improve the degradation efficiency of P&A bacterial consortium was also observed.” Figure 6 shows that there is no influence of crude oil on the removal of NAP, PHE and PYR. Correct.

Author Response

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers comments concerning our corrected manuscript entitled “Construction and degradation performance of Polycyclic aromatic hydrocarbons degrading bacterial consortium in oily sludge”. (ID: applsci-1554972 ). You can See the attachment for our reply. Thank you again for your suggestion.

I wish you all the best!

Sincerely,

Bo Yang

Author Response File: Author Response.docx