Selected Useful Properties of Polylactide Films Containing Nisaplin and Natamax

Round 1

Reviewer 1 Report

In the present paper the authors report the synthesis of nanocomposites based on polylactide (PLA) filled with nisaplin 13 and natamax for future application in the food packaging field. In my opinion there is no novelty in the reported study. It seems another composite material based on the loading of antibacterial species without any advancement in the field. Based on this I suggest the authors to modify the manuscript before its publication.

Some suggestions are below:

- Firstly the novelty in comparison to PLA composite already reported in literature should be strenghtened.

- In the materials part the authors report the chemical characteristics of ethanol, but if I well understood they did not use tis solvent in their study. Please revise

- Hoe they image the interaction of the two drugs with the polymeric matrix? It is not clear if the drugs are uniformly dispersed in the final nanocomposite.

- Figure 3b and 3c seem to be identical. Please add some explanation.

- Generally the authors present the obtained results as a mere list of experiments without a critical discussion on them. Please reconsider these parts.

English is fine

Author Response

Dear Reviewer,

all comments are in appendix.

Best Regards

Agnieszka Richert

Author Response File: Author Response.pdf

Reviewer 2 Report

This is an interesting paper on the use of bioactive agents to add microbial properties to biodegradable polymers.

I have a couple of comments on the manuscript

1) Please include more details from the literature about biodegradable polymer modification for antimicrobial activity. Where available please also include any details about the requirements, benefits, and comparisons between these methods.

2) When referring to the percentage of nisaplin and natamax in the films please specify if the percentage is by weight or volume.

3) Please include, if available, a table of the results obtained for this work and how they compare with other results reported in the literature.

4) You identify the SEM images in figure three in the text. Please include an a description in the caption.

5) Can you please relate the purity of Chloroform used in your experiments? Was it reagent grade, HPLC grade or spectroscopic grade? Was there any residue remaining after drying that may have contaminated the films?

6) You mention that both Escherichia coli and Pseudomonas aeruginosa are Gram-negative bacteria, while Staphylococcus aureus is Gram-positive. Can you relate that fact to the resulting anti bacterial activity reported in the work? Can you include details about the biocidal mechanism of Nisaplin and Natamax and how the bacterial strain might affect this? 

There are a couple of typos and misplaced words but the English is generally fine.

Author Response

Dear Reviewer,

all comments are in appendix.

Best Regards

Agnieszka Richert

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear authors,

I have read your manuscript, and I’d like to share several comments and questions that could help you to improve the submitted version.

1)      The introduction should specify what bacteriocins have been evaluated in PLA, along with their concentrations and limitations of the current state of the art. What was the motivation for you to design and execute this work? “Bacteriocins in powder form: nisaplin and natamax (Danisco, Denmark) were added as a biocidal substance in quantities of 0.2%, 0.6%, and 1.0% [24,27,28]”. If you show that 3 different papers did exactly what you did in this work, then what is the need for this contribution exactly?

2)      How much material was dissolved in chloroform? (lines 71-74) How exactly did you mix/prepare the solutions? Details on equipment type, rpm and time would be necessary.

3)      “Their size ranged from 0.080 to 0.090 mm” (line 75), I believe that you are referring to the film thickness.

4)      The sample names are not intuitive. I’d recommend renaming them throughout the manuscript in order to match the actual concentration of the substances used. For example: instead of using LN2, you can use LN0.2, so that it directly represents the concentration of nisaplin (%).

5)      Have you tried nisaplin and natamax together? Is there any synergistic effect there? Why these substances were only studied individually?

6)      “The resulting films were measured at 20 different locations with an accuracy of ±0.001 mm.” (line 181), this should be in Materials and methods, not in the Results.

7)      Figure 3. The caption for the images should be in line 242, not in the text (lines 234-236).

8)      “It can be concluded that the higher the content of a given bacteriocin in the PLA films, the better antibacterial effect was obtained. A very similar tendency has been reported in other publication [9,35–38].” This is a very generic and intuitive observation. To better contextualize your results, you can specify the bacteriocins and the respective concentration range studied in these publications.

9)      The data in table 3 has different significant figures. Standardization would be required, so that all values reported have the same significant figures.

10)   Table 5, as well as the paragraphs before it are describing the method, therefore they should be in the Materials and methods section, not in the results.

11)   Figure 4. The scale bar should be present in every single image. The caption of this figure is very confusing, to the point that image (b) is not even listed.

12)   Lines 329-330 define a notation for mutagenicity, and then you present a different notation on the table 7 caption (line 333). It is best to use only one notation and be consistent with it.

13) The conclusions are generic, and undersell your work.   

14) 10 out of 42 references (nearly 25%) were authored/co-authored by the first author. Are all those references really needed?

Dear authors,

While the English language is mostly clear and to the point, there are some spots that need improvement. Some examples are included below:

“Symbol of sample” (line 79)

“The whole thing was covered” (lines 129, 159)

“It or the barrier properties” (line 191)

 “we are better able to understand” (line 238)

“tab” (line 296)

Additionally, the following lines need to be completely rewritten for improved grammar, clarity, coherence, and conciseness.

Lines 190-195, and lines 222-224.

Author Response

Dear Reviewer,

all comments are in appendix.

Best Regards

Agnieszka Richert

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I still have some doubts about the SEM images. The obtained morphologies were barely discussed. Is the morphology obtained related to the presence of the additive on the polymer surfaces?

In my previous revision I asked the authors how they image the interaction of the two drugs with the polymeric matrix, not the drugs simultaneously but if taking into account the drugs and polymer structures they can hypothesize a sort of interaction

In my opinion after answering to the above comments the manuscript could be accepted for publication

English is fine

Author Response

Dear Reviewer,

Thank you very much for your suggestions. We hope that our answers will be sufficient. Let's include a description below in response to your comments.

Best regards,

Agnieszka Richert

Author Response File: Author Response.pdf