Enhanced Scenedesmus obliquus Cultivation in Plastic-Type Flat Panel Photobioreactor for Biodiesel Production

Round 1

Reviewer 1 Report

Very interesting studies aimed at obtaining fats from renewable sources other than arable oily plants. I would have the following comments and questions:

1) In lines 80-83, improve the multiplication symbol that should be in the hydrate designs.

2) Why transetsrifications were used in the presence of HCL and not an alkaline during transestriction. What does 8% Methanolic HCL mean?

3) In line 213 at the formula (NH4) 2SO4 there is a lack of lower indexes

4) Is FAME production equivalent to obtaining methyl esters for GC? However, the transhastrician probably runs in other conditions.

5) The letters BC, ABC, C A appears in the drawings, and maybe a leat when reading later I could not read what these letters mean. whether they were explained in the text.

6) On the chromatogram in the figure of 12 peaks from ESTRs C16: 0 and C16: 1 is not separated. on what basis the concentration of these esters was determined. What was the internal pattern to assess the concentration of these esters?

Author Response

We, as authors of the manuscript, would like to extend our sincere thanks for your valuable comments, which have enriched the manuscript and helped make it better. The aforementioned comments have been responded to (to the best of our ability) and we hope that they were satisfactory.

Our sincere regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Recommendation: Major Revision

Comments to the Author

The topic of the manuscript is appropriately suited for publication. The manuscript is in general well written and organized. It provides a large amount of experimental data, and the work seems to be carefully executed. The authors used appropriate methods to address the aims and objectives of the study. The results obtained are also interesting and relevant. Overall, the study is technically solid and includes appropriate methods as well as pertinent results. However, and for the sake of full impact only, the authors are invited to consider the following list of suggestions and recommendations.

The reviewer has some specific comments/suggestions provided below.

Section 1:

·         Although the introduction provides general information about microalgae and photobioreactors, it lacks specific data on previous outcomes in this field. For instance, it would have been helpful to mention previous studies that examined specific challenges in microalgae cultivation in photobioreactors, yields achieved with different types of photobioreactors, or the successes and failures of biodiesel production from microalgae.

·         While the introduction alludes to the overarching goal of developing plastic-based photobioreactors for microalgae cultivation for biofuel production, it does not clearly specify the specific questions the study aims to address. For example, the introduction could have included more precise statements about research objectives, such as specific parameters of microalgae cultivation to optimize, success criteria for evaluating the effectiveness of plastic photobioreactors, or gaps in current research that the study seeks to fill.

·         A scientific introduction should provide a solid theoretical background for the study by explaining the fundamental principles it is based on. For instance, the introduction could have included explanations of microalgae photosynthesis processes, factors influencing their growth and lipid yield, characteristics of different types of photobioreactors, and the technological and economic challenges associated with biodiesel production from microalgae.

Section 2:

·         Although the section details the methods used for microalgae culture and lipid analysis, it does not provide a detailed justification for methodological choices. For instance, it is not explained why the microalgae S. obliquus was chosen as the model, nor why specific parameters such as optical density, chlorophyll content, and biomass production were selected to evaluate microalgae growth.

·         The section does not mention whether the methods used to assess microalgae growth and lipid content are commonly used in the microalgae research field or if other methods were considered and dismissed. Without this comparison, it is difficult to fully assess the validity and reliability of the results obtained.

·         Although the section mentions that all experiments were conducted in triplicates, it does not provide sufficient details on how experimental conditions were standardized to ensure result reproducibility. Details on instrument calibration, controlled environmental conditions, and sample handling procedures would have strengthened the validity of the results.

Section 3:

·         3.2. Optimization of plastic bags design on microalgal growth: The explanation for why the "4-port" design outperformed others could be strengthened. A more thorough discussion on the practical implications of these results would be beneficial.

·         3.3. Optimization of N-Source: It could be useful to discuss the commercial implications of the results, particularly in terms of biodiesel production cost.

·         3.4. Optimization of Light intensity: The discussion could be expanded to include considerations on energy efficiency and production costs.

·         3.5. Optimization of Air flow: A discussion on the technical aspects of implementing different aeration rates could be helpful.

·         3.6. Biodiesel production from S. obliquus under optimized conditions: It could be useful to discuss the economic aspects of large-scale biodiesel production.

Author Response

We, as authors of the manuscript, would like to extend our sincere thanks for your valuable comments, which have enriched the manuscript and helped make it better. The aforementioned comments have been responded to (to the best of our ability) and we hope that they were satisfactory.

Our sincere regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

We, as authors of the manuscript, would like to extend our sincere thanks for your valuable comments, which have enriched the manuscript and helped make it better. The aforementioned comments have been responded to (to the best of our ability) and we hope that they were satisfactory.

Our sincere regards

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Accept in present form