One- and Two-Step Kinetic Data Analysis Applied for Single and Co-Culture Growth of Staphylococcus aureus, Escherichia coli, and Lactic Acid Bacteria in Milk

Round 1

Reviewer 1 Report

The manuscript applsci-1371516 is based on data collected from three previous works related to the growth of Staphylococcus aureus, Escherichia coli, and lactic acid bacteria (LAB) Fresco 1010 starter culture in milk under isothermal conditions between 10 and 37 °C. While previous studies aimed to model and predict the simultaneous growth of S. aureus and E. coli with LAB in milk, this study has the purpose of comparing one- and two-step kinetic data analysis approaches to describe the growth of the same bacteria. The way the tertiary model is constructed combining primary and secondary models through the one-step approach leads to minimized errors and improved statistical indices. The results can be used in practical applications, e.g., artisanal cheese-making, where lactic acid fermentation can be better supervised from the early stages to later phases.

 

The design of the manuscript and data analysis have been carefully prepared and performed. However, there are several minor inadvertencies in the text of the manuscript. Therefore, the authors have to do some fineness corrections on the manuscript. Several examples are presented below.

 

Observations

 

L12-15 The readers might find this sentence hard to read. Consider splitting it into two sentences.

L13 Delete „for”.

L17 Delete „both”.

L19-22 The sentence may be unclear or hard to follow. Consider rephrasing it. Suggestion:

„Then, a one-step approach combined the primary Huang, Giménez, and Dalgaard model (H-GD) with the secondary square root model to simultaneously model the growth of the populations mentioned above in milk under the same conditions.”

L27 Add a comma after „fermentation”.

L35 Correct article usage by inserting „the” before „case”.

L35 Correct the spelling of „raw-milk replacing it with „raw milk”.

L36 Add a comma after „regions”.

L39 Change the wording: replace „as well as” with „and”.

L51 Change the wording for conciseness: replace „is also able” with „can”.

L55 Change the wording for conciseness: replace „be result of” with „result from”.

L65 Replace „for prediction of” with „to predict”.

L72 Remove „both”.

L74 Delete the comma after „data” and replace „produces” with „and producing”.

L107 Replace „=” with „-” after „two”.

L146-147, The nine parameters for E. coli are written in two ways: x_0-10 (L146-147) and x0,10 (Table 1, Table 3)

L244, 250, 275, Figure 1 Use the abbreviation LAB instead of Lab for lactic acid bacteria.

Author Response

Many thanks to the reviewer for all comments, we have incorporated them all.

Reviewer 2 Report

General comments:

1. The method explored by the authors combines multiple basic and secondary models and requires statistical and computer programming skills. Compared to other traditional methods, this method is complicated, and according to the author's own final conclusion, the scope of application is not complete. Maybe innovative, but a little less practical.
2. There is a lot of repetition of statements. The authors should work a little more on the language expression.

 

Specific comments:

1. Introduction:

In the introduction section, a brief introduction of the basic mathematical models can be added for better understanding.

2. Line 70-78:

There are some logical problems in this paragraph, which makes it difficult to understand the main meaning the author wants to express.

3. Line 107:

There is an error in the expression "two=".

4. Line 114 and line 136:

Two different sections have the same title “Primary and secondary models”.

5. Figure 1:

The ordinate of Figure 1 does not indicate what "N" represents and does not indicate the four specific doses, just say “different inocula of LAB Fresco in milk”.

Author Response

Dear Reviewer,

thanks for the revision, the general and specific comments.

Yes, we agree that the presented approach of the description or prediction of microbial population behaviour in co-culture can be considered less practical. We have also added mention of its possible use in exposure assessments that are carried out by specialists able to use models in their differential form.

We also hope that some of the reps have been removed.

Specific comments:

Introduction - basic mathematical models: Information on modelling consists of 20 lines (58-78), including the mention of primary, secondary and tertiary models. Then, the models used in this work are described in the methodology part in detail.

Former lines 70-78: The paragraph was rewritten a bit, hopefully, it increased its understandability.

Former lines 107; 114 and 136: The errors were corrected; the second title was deleted.

Figure 1: Thank you very much for your comment, we specified the „N“ meaning and we added „four“ prior to „different inocula of LAB“ and specific LAB inoculation density in brackets.

Reviewer 3 Report

I would like to thank you for the opportunity to participate in the review of the scientific article.

The introduction to the article contains the necessary information introducing the reader to the essence of the publication. The methodology is very well written, which allows the researchers to repeat the research efficiently. The article presents a very innovative approach, using complex microbiological prediction formulas, which deserves special attention and arouses admiration in the reviewer.

Below are some minor remarks that need to be improved.

• Page 2, line 91 - Please change the microorganisms from "Streptococcus thermophilus" to the full name "Streptococcus salivarius thermophilus" (according to the manufacturer's information)
• Page 3, line 93 - The method from the ISO 4833-1: 2013 standard recommends determining the number of coli by the deep inoculation method at a temperature of 30°C (not 37°C).
• The tables do not contain the appropriate units indicated in square brackets.
• The abbreviations in the tables should be explained below.

After a slight revision of the manuscript, I recommend the article for further publication stages.

Author Response

• Page 2, former line 91:  We changed the name of S. thermophilus to its full name.
• Page 3, former line 93 - remark on the method from the ISO 4833-1: Yes, it is correct; however, there was an error, as the E. coli counts were determined according to National Standard Method F23 as we changed in the text. Thank you for this comment as we improved the Materials section.
• The units in the Tables: The units were added to the Tables. However, some of them are dimensionless.
• The abbreviations mentioned in all Tables were explained below.