Isolation, Degradation Performance and Field Application of the Metolachlor-Degrading Fungus Penicillium oxalicum MET-F-1
, Junfeng Liang 1, Yang Sun 1,*, Lixia Zhao 1, Bin Zhou 1, Xiaojing Li 1 and Yongtao Li 2,*Round 1
Reviewer 1 Report
The manuscript by Xingping Chang et al. describes about biodegradation of metolachlor by isolated fungi, Penicillium oxalicum sp. MET-F-1. Authors successfully obtained metolachlor resistant fungi for enrichment culture, and evaluate its ability for the degradation through several analysis. All contents in this manuscript were well-described and well-written. Overall, it would be suggested that current version is sufficient enough for the acceptance as good quality publication.
Author Response
We sincerely appreciate the encouragement and suggestions of the reviewer.
Reviewer 2 Report
The studies are a complete and comprehensive. Authors isolated and identified a strain with good performance on metolachlor degradation, proposed a possible pathway of metolachlor degradation, optimized the environmental conditions for the growth of the fungal strain and verified the effectiveness of the strain in a complex field environment.
I have some comments that can improve the manuscript quality.
Title of manuscript must contain the name of fungus and strain.
Abstract and aim of the study (in introduction) should contain information that fungus was isolated from the activated sludge.
In introduction list several crops in which metolachlor is applied, for example the main crops in your country (page 1, line 39).
Page 1, line 42-43. The solubility of metolachlor in water is not high. It is defined as slightly soluble in water (https://pubchem.ncbi.nlm.nih.gov/compound/Metolachlor or https://cameochemicals.noaa.gov/chemical/17824). This sentence must be changed.
Page 2, line 74 - Reference standards should be of analytical grade not of technical grade as authors wrote in this sentence.
Page 2 lines 84-87 – this sentence should contain verb for example were prepared.
Page 4 – Authors do not describe preparation of soil samples before metolachlor analysis. This information should be added.
In Results more information on degradation of other pollutants by Penicillium oxalicum should be added.
Author Response
Reviewer 2:
Comments and Suggestions for Authors
The studies are a complete and comprehensive. Authors isolated and identified a strain with good performance on metolachlor degradation, proposed a possible pathway of metolachlor degradation, optimized the environmental conditions for the growth of the fungal strain and verified the effectiveness of the strain in a complex field environment.
I have some comments that can improve the manuscript quality.
Response: We sincerely appreciate the encouragement and suggestions of the reviewer. Responses to particular comments and questions are presented in the following Point-to-Point Response.
Title of manuscript must contain the name of fungus and strain.
Response: Thank you for your good suggestions, the title of the manuscript has been modified as “Isolation, degradation performance and field application of the metolachlor-degrading fungus Penicillium oxalicum MET-F-1”.
Abstract and aim of the study (in introduction) should contain information that fungus was isolated from the activated sludge.
Response: The sentences were modified as “We isolated the fungal strain MET-F-1 from an activated sludge…” in the abstract and “The aim of this study was to isolate and identify a strain with good performance on metolachlor degradation from an activated sludge and to propose a possible pathway of metolachlor degradation” in the aim of the study. See the revised manuscript for details, please.
In introduction list several crops in which metolachlor is applied, for example the main crops in your country (page 1, line 39).
Response: The sentence was added with “such as corn, soybeans, cotton, which are the main crops in China”. See the revised manuscript for details, please.
Page 1, line 42-43. The solubility of metolachlor in water is not high. It is defined as slightly soluble in water (https://pubchem.ncbi.nlm.nih.gov/compound/Metolachlor or https://cameochemicals.noaa.gov/chemical/17824). This sentence must be changed.
Response: Thanks for the reviewer’s reminder, the sentence is not precise enough, and it is modified as “its higher water-solubility (530 mg/L, 20 °C) compared with other chloroacetamide herbicides”.
Page 2, line 74 - Reference standards should be of analytical grade not of technical grade as authors wrote in this sentence.
Response: Thanks for the reviewer's meticulous work and sorry for our carelessness. It has been modified as suggested.
Page 2 lines 84-87 – this sentence should contain verb for example were prepared.
Response: It has been modified as suggested. See the revised manuscript for details, please.
Page 4 – Authors do not describe preparation of soil samples before metolachlor analysis. This information should be added.
Response: It has been modified as “Metolachlor and its metabolites in the liquid and soil samples were analyzed as follows. Two milliliters of the liquid sample or 2.0 g of the soil sample was placed in a 50 mL polypropylene centrifuge tube containing 10 mL of acetonitrile, and 2.0 g of sodium chloride”.
In Results more information on degradation of other pollutants by Penicillium oxalicum should be added.
Response: Thanks for the reviewer's meaningful recommendation. However, due to the limitation of time, we are unlikely to add this part of the experiment in this paper. This suggestion is good, and this part of the experiment will be reflected in the follow-up work.
Reviewer 3 Report
General comments:
Authors studied the biodegradation of the herbicide metolachlor by an isolated strain identified as Penicilium oxalicum sp. in contaminated soils and proposed a possible degradation pathway. The effectiveness of the strain was verified in a field experiment.
Novelty is based in: i) the isolation and identification of a new fungal strain with metolachlor-degrading potential and, ii) evaluation of its effectiveness for biodegradation of metolachlor under field conditions. In general, the quality of work is high and meets with the Journal requirements. Methods are adequately and explicitly stated in the manuscript and supporting information. The results present a great interest and significance for the field of environmental sciences and soil remediation. Results are well presented and adequately discussed. The future work should be clearly stated.
Specific comments:
Abstract
More accurate results could be included in the abstract; for example, in Line 23 indicate the metabolites found and in Lines 27-28 indicate percentage of degradation in the field experiment.
Materials and methods
Lines 69-72. Please correct the title of this subheading. Some physicochemical properties of the activated sludge (soil?) could be included in this subsection.
Lines 131-132. Specify ranges of metolachlor concentrations, pHs, temperatures and culture times assayed to optimize metolachlor degradation performance of strain MET-F-1.
Line 145. Please indicate soil classification source.
Lines 148-149. Indicate metolachlor concentration as weight of herbicide per hectare or weight of herbicide per weight of soil.
Results and Discussion
Lines 286-289. Explain better why the initial concentrations of metolachlor were different for the three treatments assayed.
Lines 313-314. Do you plan to carry out these field tests in the future? Please specify.
Author Response
Reviewer 3:
Comments and Suggestions for Authors
General comments:
Authors studied the biodegradation of the herbicide metolachlor by an isolated strain identified as Penicilium oxalicum sp. in contaminated soils and proposed a possible degradation pathway. The effectiveness of the strain was verified in a field experiment.
Novelty is based in: i) the isolation and identification of a new fungal strain with metolachlor-degrading potential and, ii) evaluation of its effectiveness for biodegradation of metolachlor under field conditions. In general, the quality of work is high and meets with the Journal requirements. Methods are adequately and explicitly stated in the manuscript and supporting information. The results present a great interest and significance for the field of environmental sciences and soil remediation. Results are well presented and adequately discussed. The future work should be clearly stated.
Response: We sincerely appreciate the encouragement and good suggestions of the reviewer.
Specific comments:
Abstract
More accurate results could be included in the abstract; for example, in Line 23 indicate the metabolites found and in Lines 27-28 indicate percentage of degradation in the field experiment.
Response: This suggestion has been followed. See Page 1, Line 24.
Materials and methods
Lines 69-72. Please correct the title of this subheading. Some physicochemical properties of the activated sludge (soil?) could be included in this subsection.
Response: This suggestion has been followed. Here are some of the additions: with the pH of 6.75, the organic matter content of 73.66 g kg-1, the total nitrogen content of 2.4 g kg-1 and the total phosphorus of 1.54 g kg-1. Sludge texture consisted of 64.1% sand, 25% silt and 10.9% clay. See Page 2, Line 71-76 for details, please.
Lines 131-132. Specify ranges of metolachlor concentrations, pHs, temperatures and culture times assayed to optimize metolachlor degradation performance of strain MET-F-1.
Response: This sentence was modified as “the effects of metolachlor concentration of 5-100 mg/L, pH of 5.0-7.5, temperature of 20-35 °C, and culture time of 0-140 hours on its metolachlor-degrading potential were investigated using a completely randomized design”.
Line 145. Please indicate soil classification source.
Response: The soil classification is from the reference of “Sun, Y., L. Zhao, X. Li, et al., Stimulation of earthworms (Eisenia fetida) on soil microbial communities to promote metolachlor degradation. Environ. Pollut., 2019. 248: p. 219-228”.
Lines 148-149. Indicate metolachlor concentration as weight of herbicide per hectare or weight of herbicide per weight of soil.
Response: This suggestion has been followed. The unit has been converted to kg/ha. See Page 4, Line 153 for details, please.
Results and Discussion
Lines 286-289. Explain better why the initial concentrations of metolachlor were different for the three treatments assayed.
Response: The content of “due to the complexity of field environment” was changed to “due to the uneven plowing and sampling error in the field environment”.
Lines 313-314. Do you plan to carry out these field tests in the future? Please specify.
Response: Yes, we will continue this work. To evaluate the influence of complicated factors on the metolachlor-degrading potential of the strain MET-F-1, we will perform multiple orthogonal experiments in field environments of different seasons and soil classifications. Besides, we arrange to verify the degrading potential of strain MET-F-1 for other pesticides.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
