ε-Polylysine Derived from Marine Bacteria-A Possible Natural Preservative for Raw Milk Storage
, Sandhya Mishra 2,*, Antonio Zuorro 3, Heba Hassan Salama 4, Alexandru Vasile Rusu 5 and Monica Trif 6,*Round 1
Reviewer 1 Report
Dear Authors,
here are my comments on the manuscript.
Best Regards
The manuscript can be reconsidered after suggested major revision.
Lines 133: is: 37°C, should be 37 °C and should be included throughout the text…
Line 136: is: 100 ml, should be 100 mL. Please correct the units throughout the text.
Line 143: is: (g/l), should be g/L) . Please correct the units throughout the text.
Line 235: 2ml, there should be a space between the number and the unit…
Line 402: is: 48h, there should be a space between the number and the unit…
Figure 3 should be replaced with a more clear and professional one. This one is unacceptable.
Figure 5 should be replaced with a more clear and professional one. This one is unacceptable.
In Table 3 and 4, 5, 6 numerical values should be standardized to the same number of decimal places...
Figure 6 needs to be changed, this one is illegible.
The drawing (Fig.4) is hard to read, please correct it
Points 2.2 and 2.3 should be extended, they are currently too general and briefly described.
Author Response
Dear Reviewer,
We are extremely thankful for polishing the manuscript further through scrutinizing the manuscript minutely to enable this manuscript giving a final shape as desired for the journal.
Please find below the reply to your comments for the manuscript entitled “ε-Polylysine derived from marine bacteria - a natural preservative for raw milk storage” as desired.
Comment 1: Lines 133: is: 37°C, should be 37 °C and should be included throughout the text…
Reply to Comment 1: We have incorporated desired changes in the revised manuscript as per reviewer’s suggestions.
Comment 2: Line 136: is: 100 ml, should be 100 mL. Please correct the units throughout the text.
Reply to Comment 2: We have revised the manuscript as per reviewer’s suggestions.
Comment 3: Line 143: is: (g/l), should be g/L) . Please correct the units throughout the text.
Reply to Comment 3: We have incorporated desired changes in the revised manuscript as per reviewer’s suggestions.
Comment 4: Line 235: 2ml, there should be a space between the number and the unit…
Reply to Comment 4: We have incorporated desired changes in the revised manuscript as per reviewer’s suggestions.
Comment 5: Line 402: is: 48h, there should be a space between the number and the unit…
Reply to Comment 5: We have revised the manuscript as per reviewer’s suggestions.
Comment 6: Figure 3 should be replaced with a more clear and professional one. This one is unacceptable.
Reply to Comment 6: We have revised the manuscript as per reviewer’s suggestions. We have removed the Figure 3 as already NMR of ε-polylysine is present in the manuscript which clearly confirms the structure of ε-polylysine and hence, Poly acrylamide gel electrophoresis (PAGE) of ε-PL is not required in the present manuscript.
Comment 7: Figure 5 should be replaced with a more clear and professional one. This one is unacceptable.
Reply to Comment 7: We have revised the manuscript as per reviewer’s suggestions. Figure 5 is replaced with a table showing detailed microbiological analysis of milk samples without ε-PL, with 0.02% w/v ε-PL, with 0.02% w/v ε-polylysine + 0.1 % w/v NaHCO3 and with 0.02% w/v ε-polylysine + 0.2 % w/v NaHCO3. Further, the table on microbiological analysis of milk samples clearly mentions the total plate count and coliform counts of the samples which give a quantitative analysis of the microbial growth and shows a clearer picture with respect to the figure on microbial growth.
Comment 8: In Table 3 and 4, 5, 6 numerical values should be standardized to the same number of decimal places...
Reply to Comment 8: We have incorporated desired changes in the revised manuscript as per reviewer’s suggestions.
Comment 9: Figure 6 needs to be changed, this one is illegible.
Reply to Comment 9: We have revised the manuscript as per reviewer’s suggestions. Figure 6 is replaced with a table showing detailed microbiological analysis of milk samples without ε-PL, with 0.02% w/v ε-PL, with 0.02% w/v ε-polylysine + 0.1 % w/v NaHCO3 and with 0.02% w/v ε-polylysine + 0.2 % w/v NaHCO3.
Comment 10: The drawing (Fig.4) is hard to read, please correct it.
Reply to Comment 10: We have incorporated desired changes in the revised manuscript as per reviewer’s suggestions.
Comment 11: Points 2.2 and 2.3 should be extended, they are currently too general and briefly described.
Reply to Comment 11: As per reviewer’s comment, we have revised the manuscript and extended the section 2.2 and 2.3 in the manuscript.
Reviewer 2 Report
This work is interesting as it describes the preparation and characterization of ε-Polylysine as a potential natural food preservative. The authors examined the effect of ε-Polylysine on microbial growth and pH development in milk. They also assessed its influence on relevant chemical properties of milk. My main concern is that it is not clear which microbial species are inhibited by ε-Polylysine. The authors added the preservative into milk samples and looked at total microbial growth and pH. Since the microflora of milk samples can vary depending upon different factors, the results of preserving milk using ε-Polylysine can not be generalized. A set of further experiments in which the authors inoculate milk with specific bacterial species and assess the antibacterial effect of ε-Polylysine on them should be carried out. There is also a need to assess the effect of ε-Polylysine and ε-Polylysine + bicarbonate on the sensory properties of milk samples.
Other comments:
- The manuscript needs revision for the correction of grammatical mistakes, e.g. line 132 " The media was….", line 331 "…growths…", etc..
- The quality of figures 3, 5 and 6 is poor. These figures can be eliminated.
- What is meant by a "fundamental dye" line 126?
Author Response
Dear Reviewer,
We are extremely thankful for polishing the manuscript further through scrutinizing the manuscript minutely to enable this manuscript giving a final shape as desired for the journal.
Please find below the reply to your comments for the manuscript entitled “ε-Polylysine derived from marine bacteria - a natural preservative for raw milk storage” as desired.
Comment 1: This work is interesting as it describes the preparation and characterization of ε-Polylysine as a potential natural food preservative. The authors examined the effect of ε-Polylysine on microbial growth and pH development in milk. They also assessed its influence on relevant chemical properties of milk. My main concern is that it is not clear which microbial species are inhibited by ε-Polylysine. The authors added the preservative into milk samples and looked at total microbial growth and pH. Since the microflora of milk samples can vary depending upon different factors, the results of preserving milk using ε-Polylysine cannot be generalized. A set of further experiments in which the authors inoculate milk with specific bacterial species and assess the antibacterial effect of ε-Polylysine on them should be carried out. There is also a need to assess the effect of ε-Polylysine and ε-Polylysine + bicarbonate on the sensory properties of milk samples.
Reply to Comment 1: We have revised the manuscript as per reviewer’s suggestions. Table 4 clearly shows the list of specific bacterial species which were inhibited by addition of ε-polylysine.
Lafta et al., 2019 have done the sensory analysis of drinking yoghurt containing 0.007% (w/v) ε-polylysine. However, according to the sensory analysis results based on taste, colour, odour, mouthfeel and appearance, it was found that ε-polylysine at a concentration of 0.007% (w/v) provided desirable sensory characteristics with better mouthfeel properties as compared to other preservatives. Further, ε-polylysine was found to control post-acidification through inhibiting post-fermentation of lactic acid bacteria.
ε-polylysine is being used as natural food preservative in many of the food products and also have been approved as GRAS (Generally Recognized as Safe Food Preservative). Further, ε-polylysine is being reported to inhibit broad range of Gram positive and Gram negative bacteria and also reported as an important antibacterial agent for various applications in various sectors.
Comment 2: The manuscript needs revision for the correction of grammatical mistakes, e.g. line 132 " The media was….", line 331 "…growths…", etc..
Reply to Comment 2: We have revised the manuscript as per reviewer’s suggestions.
Comment 3: The quality of figures 3, 5 and 6 is poor. These figures can be eliminated.
Reply to Comment 3: We have incorporated desired changes in the revised manuscript as per reviewer’s suggestions.
Comment 4: What is meant by a "fundamental dye" line 126?
Reply to Comment 4: In line 126, Methylene Blue was considered as fundamental dye. However, we have removed the word ‘fundamental dye’ with the ‘Methylene Blue Dye’.
Round 2
Reviewer 1 Report
Dear Authors,
Thank you for including the corrections. I currently have no comments.
Best Regards
Author Response
Dear Reviewer,
Thank you for your time and guidance. Best regards.
Reviewer 2 Report
The authors have addressed my comment on the effect of ε-polylysine on the sensory properties of dairy products. They also provided Table 4 to show the effect of the preservative on specific bacterial species. However, there are a number of species in this table including Salmonella, Staphylococcus aureus, Listeria mononcytogenes and Clostridrium perfringens that could not be originally detected in milk (absent) without the addition of ε-polylysine. They would certainly be absent in milk after adding ε-polylysine. In this case, it can't be concluded that ε-polylysine eliminated those species. The authors need to do another experiment using UHT milk, to which pure cultures of those bacterial species are added and examined for their presence after the addition of ε-polylysine.
The writing of the manuscript still needs revision and improvements.
Author Response
Dear reviewer,
We are extremely thankful for helping us in polishing the manuscript further through scrutinizing the manuscript minutely to enable this manuscript giving a final shape as desired for the journal.
Please find below the reply to your comments for the manuscript entitled “ε-Polylysine derived from marine bacteria - a natural preservative for raw milk storage” as desired.
Reviewer Comments
Comment1: The authors have addressed my comment on the effect of ε-polylysine on the sensory properties of dairy products. They also provided Table 4 to show the effect of the preservative on specific bacterial species. However, there are a number of species in this table including Salmonella, Staphylococcus aureus, Listeria mononcytogenes and Clostridrium perfringens that could not be originally detected in milk (absent) without the addition of ε-polylysine. They would certainly be absent in milk after adding ε-polylysine. In this case, it can't be concluded that ε-polylysine eliminated those species. The authors need to do another experiment using UHT milk, to which pure cultures of those bacterial species are added and examined for their presence after the addition of ε-polylysine.
Reply to Comment 1: We have incorporated desired changes (highlighted in green) in the revised manuscript as per reviewer’s suggestions.
Comment 2: The writing of the manuscript still needs revision and improvements.
Reply to Comment 2: We have revised the manuscript as per reviewer’s suggestions.
Thank you again for your guidance.
