Small-Scale Bioreactor for Sterile Hydroponics and Hairy Roots: Metabolic Diversity and Salicylic Acid Exudation by Hairy Roots of Hyoscyamus niger
Round 1
Reviewer 1 Report
The manuscript is very strong and fulfills all requirements necessary for publication in MDPI Applied Sciences.
On the very positive side
1. Its subject is definitely interesting and deals with important aspects of plant science.
2. It reports on a very thorough work (the introduction and the experimental parts are exceptionally well-written).
3. It contains plenty of data, and
4. The data are correctly interpreted.
Based on the above statements, the paper may be published (after certain minor corrections) in its current form.
On the less positive side:
1. In the paper, it ought to be clearly expressed why the work was started: what were the essential objectives and what was the premise of choosing the particular experimental strategies and the plant species investigated.
2. The results of the study are solid - but the relationships are not established clearly: what are the key (genetic, environmental, etc.) factors that led to the observed phenomena?
3. A few words need to be added about the statistical methods used.
4. In the paper, it should be specified what was new and original in the methods used (e.g., is the bioreactor a new design?) and also in the findings of the study.
Overall, my view on the paper is very positive, and a questions and minor comments and questions are readable on the attached manuscript.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
The current manuscript described the development and validation of a novel bioreactor design for cultivation of plant tissue and the collection of root exudates. The experiments were conducted properly and the manuscript is nearly suitable for publication.
Major Comments
The authors note that oxygen availability to root systems is one of the major abiotic factors affecting growth, biomass and concentration and diversity of metabolic exudates into culture media with respect to bioreactors. Did the authors measure dissolved oxygen levels throughout the experiment to validate availability to root surface? If so, did the DO level change as biomass increased throughout the studies? Additionally, what was the percent saturation of DO in the culture solution throughout the studies? With regards to this, was the use of micro or nano bubble generator technology or liquid oxygen or ozone considered for use in these trials in lieu of simple air bubblers? Please either include these data or address this concept in the text.
Minor Comments
1) Did the authors conduct proximate analyses on the dry hairy root biomass to determine incorporated nitrogenous or organic compounds? If so, was there a difference due to culture method?
2) LINE 285: "tThe" should be changed to "The"
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript titled ”Small-Scale Bioreactor for Sterile Hydroponics and Hairy Roots: Metabolic Diversity and Salicylic Acid Exudation by Hairy Roots of Hyoscyamus niger”, validated the suitability of a small-scale bioreactor as opposed to shaking flasks, fabricated from standard glass materials, by growing oilseed rape, rose plants and hairy roots of henbane and sesame. Even though plants are a source of a variety of secondary metabolites, and many efforts had being done in order to obtain a bioreactor configuration for highest biomass possible, there is a still a demand of improved bioreactors that will minimized shear stress and better oxygen uptake.
General comments and Recommendations:
Even though the manuscript it is related with the aims and scopes of “applied sciences”, for my review, this paper has many limitations, that have to do with the general merit of the manuscript. There is a failure from authors to follow the instruction for authors. For example the “application example session” instead of results and discussion is complicated and information given in many cases belongs to the material and method session. The manuscript will be improved by a clearly separation of “results” and a “discussion” session. In line discussion session is very poor.
In the manuscript you must indicated clearly references.
For example Row 154: “12 h per day”. According to whom recommendations? Please clarify.Row 184-186: According to whom recommendations? And so on…
It is important, when you describe procedures you must mention according to …….. or protocols that followed.
The manuscript will be improved by statistical analysis between treatments.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
In the revised version the authors suggesfully addressed all comments.
The manuscript has been improved in a great extent.
