Study of the Influence of the Temperature and Time of Microalgae Cultivation on the Reproduction Rate of Chlorella and Scenedesmus Microalgae When Cultured in a Tubular Photobioreactor

Round 1

Reviewer 1 Report

Title & aim:

The title and aim are very basic, and nothing new to be published.

The optimum temperature and cultivation time for Chlorella and Scenedsmus is known and well established

Introduction:
The introduction also mentioned well-known information without a clear explanation of the importance of the experiment.

Materials and methods: 
What is the point of using a bioreactor for growth measurements!!!

and how you tested many temperature values in the experiment ???

growing algae for several weeks is a long time for production and not economic

no statistical analysis mentioned or significance

Results:

All results are expected, and nothing new

The discussion is clear, but it is fundamental knowledge for any specialist in microalgae

Conclusion the same

References are just 15 with non-significant value 

Author Response

Greetings, dear reviewer!

Thank you so much for your comments on our work, it will allow us to think critically about our work and continue with new ideas.

A few words in response to your remarks.

The global purpose of our work is to try to develop a green integrated process for efficient utilization of waste discharge (CO₂ as carbon and energy source) for co-production of microalgae biomass feedstock, in the waste-to-value chain, and waste management for sustainable future development.

The main goal of this process is, first of all, to solve the problem of carbon dioxide utilization with an increase in the efficiency of carbon dioxide biofixation by microalgae in a closed photobioreactor. In this regard, all experiments to study the parameters of microalgae cultivation were carried out in an automatic laboratory tubular photobioreactor designed by us. That is why we are trying to obtain data on temperature, pH and time, which could be used as input data for the design of the technological process for the utilization of carbon dioxide.

Increasing the cultivation time was undertaken to obtain regularities of the influence of certain parameters on growth over time. Of course, in terms of the cost-effective process, such time lapses are not beneficial. In this regard, we will select less time, taking into account the maximum fixation of carbon dioxide by microalgae.

We tried to specify the title of the work in accordance with our goal to study the conditions of cultivation of microalgae with their approximation to the conditions of the planned technological process of carbon dioxide utilization.

All experimental data are presented as averaged according to the results of 6-7 independent experiments, the average statistical error is 10-15%.

The obtained data are now used to prepare the initial data for the design of the process line using tubular photobioreactors and microalgae specifically selected by us in this work.

We really hope for support in publishing our article!

Thank you for your understanding!

Sincerely yours, the authors

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript, while straightforward, effectively incorporates its intended goals within its results through an appropriate methodology consistent with various studies on microalgae cultivation. However, there are some inaccuracies within the text (referenced in the attached PDF) that could be promptly addressed by the authors.

I suggest that the authors take care to cite other authors’ findings more diligently in the discussion. Additionally, maintaining a consistent use of the simple past tense is advisable, considering the completed nature of the conducted experiments.

Overall, I recommend that the manuscript be accepted after review.

Additional comments to the authors can be found in the attached file.

Comments for author File: Comments.pdf

Author Response

Greetings, dear reviewer!

Thank you so much for your comments on our work, it will allow us to think critically about our work and continue with new ideas.

We took into account all your comments and made appropriate changes to the text.

Several articles have been added to the reference list over the past 3 years.

Thank you very much for your feedback.

We really hope for support in publishing our article!

Thank you for your understanding!

Sincerely yours, the authors

Reviewer 3 Report

The author claimed to have investigated hte growth performance of Chlorella vulgaris and two species of Scenedesmus, fuscus and obliquus, concluding that Chlorella performed well in terms of increased biomass compared to the other two Scenedesmus species under the culture conditions investigated

In what follows a series of points that should be carefully dressed by the authors:

In lines 193-194 they reported “From Figures 2 and 4 it is seen that microalgae Chlorella vulgaris have twice the biomass productivity than microalgae Scenedesmus fuscus and Scenedesmus obliquus”. Anyway in Figure 4 is not reported the growth of Scenedesmus obliquus but only that of  S. fuscus and Chlorella. Therefore this figure should be revised by adding the dependence of S. obliquus growth. Same mistake referred to lines 210-212 when discussing about biomass accumulation and CO2 absorption capacity  of the three strains

In figure 3, why is not reported the dependence of S. obliquus growth as function of pH?

In figure 2, concentration of microalgae should be substituted by biomass concentration

Line 103, it should be specified that 20 klk is the light intensity, so “the microalgae suspension was illuminated by X lamps/LED providing a light intensity of 20 klk”

Line 104, something is wrong here since 8 + 12 is 20 h not 24 h, is the light cycle 12 h light and 12 h dark?

Line 133, nitrate nitrogen. The authors want to say that nitrogen is supplied in terms of nitrate? Specify

Line 204-206. The whole sentence should be re-phrased since it does not sound very fluent (to many “of”)  

In the manuscript sometime the authors refer to carbon dioxide in words and sometime in symbol, even in the same phrase. For example, in line 27 is reported for the first time the word CO2 in symbol and two lines later (29) in words. Authors should express in line 22 carbon dioxide (CO2) and, after that, every time they refer to carbon dioxide refer to it as CO2. From that point on refer only to CO2 for all the manuscript instead of carbon dioxide (see lines 45, 47, 118, 146)

Conclusions should not be a list of finding in numerical order (as for the highlights provided to the journal)  but  should instead stand alone as a brief paragraph where authors should emphasize the importance of their study (why they choose to do it, what their findings have proven/reported, and how these findings could answer to missing gap in the field). Authors should refine this paragraph

In the reference list the authors should be aware that the name of all the strains reported should be in Italics (see line 265)

The authors should also update their research to most recent advances in the field. On 15 references reported the most recent relied on 2018, while a lots of works cited are related to a period from 2011 to 2015. Nobody has progressed in this field in 2023, 2022, 2021, 2020 etc?

I would suggest also the authors to refine their title as follows “Effect of temperature and culture time on reproduction rate of microalgae belonging to Chlorella and Scenedesmus genera”

Broadly speaking the authors should refine their whole manuscript with particular attention to the syntax by eliminating small inaccuracies. I suggest to paid attention to the frequent use of the word "of" which makes some phrases too redundant and to avoid writing sentences too long.

Author Response

Greetings, dear reviewer!

Thank you so much for your comments on our work, it will allow us to think critically about our work and continue with new ideas.

We have taken into account all your remarks and comments. Thank you very much for such a great job.

We have added graphs 3 and 4 data for Scenedesmus obliquus.

We took your comments into account on the following points and added clarifications or corrected them.

We tried to summarize the conclusions in accordance with your comment. The conclusions have been finalized.

We have also supplemented the list of references with works over the past three years.

And we changed the title of the article; your proposal for the title of our work is really better than the original version.

We really hope for support in publishing our article!

Thank you for your understanding!

Sincerely yours, the authors

Round 2

Reviewer 1 Report

Thank you for your reply and corrections.

Reviewer 3 Report

The title sounds to be a little bit confusing after changes were made. I suggest the authors to refine it. Paid attention that in the same sentence are reported twice the words microalgae and cultivation/cultured

An option could be: Growth of Chlorella and Scenedesmus strains in a tubular photobioreaactor: How temperature and cultivation time influence microalgae reproduction rate.

Be aware that in line 65-66 is still reported carbon dioxide in words instead of CO2

The quality of English has been improved