Microplastic Accumulation and Degradation in Environment via Biotechnological Approaches
Round 1
Reviewer 1 Report
In the presented work, Thakur et al., focuses on plastic bioaccumulation in the trophic chain as well as means on combatting the pollutant
The abstract gives percentages, please remove them or state citation for them later in the article main body
Introduction
Line 34-35: "Plastics are made up of natural, organic materials such as cellulose, coal, natural gas, salt and, of course, crude oil." Please clarify this sentence, perhaps better of you change it completely (i.e. https://plasticseurope.org/plastics-explained/how-plastics-are-made/).
There are 7 classes of plastic, please state them in detail of composition, also state which ones are recyclable.
Conclusions need to better reflect the scope of the work
Overall it's a good article, the authors have managed to covered concisely all important aspects
Author Response
In the presented work, Thakur et al., focuses on plastic bioaccumulation in the trophic chain as well as means on combatting the pollutant
The abstract gives percentages, please remove them or state citation for them later in the article main body.
Reply: As per the suggestion we have removed the % from the abstract and placed in the body of the text with citation.
Introduction
Line 34-35: "Plastics are made up of natural, organic materials such as cellulose, coal, natural gas, salt and, of course, crude oil." Please clarify this sentence, perhaps better of you change it completely (i.e. https://plasticseurope.org/plastics-explained/how-plastics-are-made/).
Reply: We thank for the suggestion of the respected reviewer and therefore changed the line as “Plastics are produced from different natural products following a polymerisation or polycondensation process. The composition of plastics is therefore natural and organic materials. For example, cellulose, coal, natural gas, salt and, crude oil etc act as the raw materials for the production of plastics.”
There are 7 classes of plastic, please state them in detail of composition, also state which ones are recyclable.
Reply: Thank you for the suggestion. We have included almost a paragraph in section 4 with appropriate reference to include the 7 types of plastics and degradation nature them.
Conclusions need to better reflect the scope of the work
Overall it's a good article, the authors have managed to covered concisely all important aspects.
Reply: We have modified the conclusion to make it more clearly and as per the scope of the work.
Reply: We are highly thankful to the referee for these encouraging comments.
Reviewer 2 Report
The manuscript presents an interesting topic of microplastic accumulation in environment and the biotechnological degradation. The manuscript is well written and describes both theoretical and technical analysis, which is very timely for the understanding of microplastic pollution. There are some concerns which are described below.
1. The introduction is not well-written, and some important issues are ignored.
(1) In the first paragraph, the general information of plastic wastes needs more in-depth discussions, including the applications of plastics and production of plastic wastes. Key references are suggested: Environmental Functional Materials, 2022, 1: 34-48.; Science, 371(6530), 672-674.; Water Research X, 2022, 17: 100155.
(2) In the second paragraph, the discussion of removal/degradation of microplastics and nanoplastics should be enhanced, important references should be cited: Water Research, 2022, 221: 118846.; Water Research, 2022, 221: 118820.; Chemical Engineering Journal 404 (2021): 127079.; Water Research X, 2019, 3: 100030.
2. In the second part, the effect of microplastics on water environment should be discussed, especially on the biochemical wastewater process: Environmental Science & Technology 54.12 (2020): 7037-7049.; Water Research 202 (2021): 117417.
3. The full name of PVC, PP, PS, etc. should be provided.
4. Improve the overall quality of figures, especially Figures 2, 5-7.
5. Many grammatical errors in the paper. Please improve the quality of English and highlight all changes that you have made in the revised version for improving readability.
6. In the final part, provide in-depth analysis on the further development of microplastic transformation and biodegradation.
Comments for author File: 
Comments.pdf
Author Response
The manuscript presents an interesting topic of microplastic accumulation in environment and the biotechnological degradation. The manuscript is well written and describes both theoretical and technical analysis, which is very timely for the understanding of microplastic pollution. There are some concerns which are described below.
Reply: We are highly thankful to the referee for these encouraging comments. And we have revised the manuscript strictly following the respected referee’s comments.
- The introduction is not well-written, and some important issues are ignored.
(1) In the first paragraph, the general information of plastic wastes needs more in-depth discussions, including the applications of plastics and production of plastic wastes. Key references are suggested: Environmental Functional Materials, 2022, 1: 34-48.; Science, 371(6530), 672-674.; Water Research X, 2022, 17: 100155.
Chen, Z.; Wei, W.; Ni, B.J.; Chen, H. Plastic wastes derived carbon materials for green energy and sustainable environmental applications. Environ. Func. Mat., 2022, 1(1), 34-48, https://doi.org/10.1016/j.efmat.2022.05.005.
The paper was referred and included as part of introduction as.
Certain properties of plastic like being highly flexible, resistant to corrosion, high strength-to-weight ratios and low costs in carrying out fabrication work has resulted in high usage of plastics in packaging, in the field of construction and transportation and production of electrical, medical and electronic devices [5]
Vethaak, A.D.; Legler, J. Microplastics and human health. Sci. 2021, 371(6530), 672-674. https://doi.org/10.1126/science.abe5041.
The paper was referred and included as part of introduction and effect of microplastics on human health and written as as
Microplastics have a variety of shapes like spheres, fragments, fibers [10]. Scarcity of proper analytical tools for isolation, detection, quantification and characterization of microplastic particles which are <10 μm has resulted in difficulty in estimating the risk of microplastics to human health. But it has been reported that particulate particles in air which are smaller than 2.5 μm in size arising from diesel exhaust have the capacity to enter the cell and induce the formation of reactive oxygen species (ROS) and inflammation and is linked to increased chances of death due to cardiovascular, respiratory diseases or lung cancer. By comparing these results with microplastics of smaller size parallel can be drawn to estimate the risk of microplastic on human health [10]
Rhein, F.; Nirschl, H.; Kaegi, R. Separation of Microplastic Particles from Sewage Sludge Extracts Using Magnetic Seeded Filtration. Wat. Res. X, 2022, 17, 100155, https://doi.org/10.1016/j.wroa.2022.100155.
The paper was referred and included as part of introduction as
The presence of microplastics in a sample and its quantification can be carried out either at individual particle level by using spectroscopic techniques like FTIR or RAMAN or by determining the total amount of microplastics present in a sample using Py-GCMS or thermal extraction desorption GC MS [15].
(2) In the second paragraph, the discussion of removal/degradation of microplastics and nanoplastics should be enhanced, important references should be cited: Water Research, 2022, 221: 118846.; Water Research, 2022, 221: 118820.; Chemical Engineering Journal 404 (2021): 127079.; Water Research X, 2019, 3: 100030.
Feng, L.A.; Liang, B.; Zeng, X.; Shi, C.; Yin, H.; Feng, Y.; Chen, Y.; Yu, Q. Engineered bacterium-binding protein promotes root recruitment of functional bacteria for enhanced cadmium removal from wastewater by phytoremediation. Wat. Res. 2022, 221, 118746, https://doi.org/10.1016/j.watres.2022.118746.
The paper has been referred and included as part of concluding remarks as
Modification of bacterial proteins to enhance their ability to remove microplastics from wastewater can be employed [128]
Chen, Z.; Liu, X.; Wei, W.; Chen, H.; Ni, B.J. Removal of microplastics and nanoplastics from urban waters: Separation and degradation. Wat. Res. 2022, 221, 118820, https://doi.org/10.1016/j.watres.2022.118820.
The paper has been referred and included as part of effect of microplastics on environment as
The innumerable applications of plastics in day-to-day life has resulted in presence of plastic wastes in large amounts in urban water systems [34].
Liu, S.Y.; Leung, M.M.; Fang, J.K.; Chua, S.L. Engineering a microbial ‘trap and release’ mechanism for microplastics removal. Chem. Eng. J., 2021, 404, 127079, https://doi.org/10.1016/j.cej.2020.127079.
The paper has been referred and included as part of concluding remarks as
Pseudomonas aeruginosa strains were engineered which were capable of removing microplastics from seawater samples by secretion of exopolysaccharides using ‘trap and release’ mechanism [127].
Conley, K.; Clum, A.; Deepe, J.; Lane, H.; Beckingham, B. Wastewater treatment plants as a source of microplastics to an urban estuary: Removal efficiencies and loading per capita over one year. Wat. Res. X, 2019, 3, 100030, https://doi.org/10.1016/j.wroa.2019.100030.
The paper has been referred and included as part of effect of microplastics on environment as
though wastewater treatment plants which used primary clarification wherein microplastics are removed based on their densities either by sedimentation or floatation before the wastewater is subjected to biological treatment have proved to be more efficient in removal of microplastics from wastewater [39].
- In the second part, the effect of microplastics on water environment should be discussed, especially on the biochemical wastewater process:Environmental Science & Technology 54.12 (2020): 7037-7049.; Water Research 202 (2021): 117417.
Elkhatib, D.; Oyanedel-Craver, V. A Critical Review of Extraction and Identification Methods of Microplastics in Wastewater and Drinking Water. Environ. Sci. Technol., 2020, 54 (12), 7037-7049. https://doi.org/10.1021/acs.est.9b06672
The paper has been referred and included as part of effect of microplastics on environment as
The presence of microplastics is also found in large quantities in drinking water. The effluents from wastewater treatment plants and stormwater runoff from urban and agricultural lands are the major sources of microplastics in drinking water [40].
Na, S.H.; Kim, M.J.; Kim, J.T.; Jeong, S.; Lee, Chung, S.J.; Kim, E.J. Microplastic removal in conventional drinking water treatment processes: Performance, mechanism, and potential risk. Wat. Res., 2021, 202, 117417, https://doi.org/10.1016/j.watres.2021.117417.
The paper has been referred and included as part of effect of microplastics on environment as
Na et al [ 41] investigated if drinking water treatment plants where the different processes of coagulation, sand filtration and disinfection using UV and UV/H2O2 can remove the microplastics from drinking water. Through their studies they concluded that the type of coagulant used and the pH and organic matter present naturally in water affect the efficiency of microplastics to coagulate. Moreover, after sand filtration atleast 16% of microplastics which were <10 μm in size were further fragmented by UV/H2O2 causing the leaching of chemicals in water resulting in increased toxicity of water sample.
- The full name of PVC, PP, PS, etc. should be provided.
Reply: The full forms are provided.
- Improve the overall quality of figures, especially Figures 2, 5-7.
Reply: We have provided the raw figures which shall solve this issue now. When the pictures were copy pasted on the ms, they were not with high resolution.
- Many grammatical errors in the paper. Please improve the quality of English and highlight all changes that you have made in the revised version for improving readability.
Reply: We have revised the ms with a language expert and all the changes are highlighted in red colored text. Line numbers 38 and 39 are reframed and rest corrections are done in red font in the manuscript
- In the final part, provide in-depth analysis on the further development of microplastic transformation and biodegradation.
Reply: We have made the necessary changes in the conclusion.
Round 2
Reviewer 2 Report
accept!
