Enhancing Docosahexaenoic Acid Production of Isochrysis galbana from Starch-Rich Food Processing Byproducts
Round 1
Reviewer 1 Report
The article "Enhancing docosahexaenoic acid production of Isochrysis galbana from starch-rich food processing byproducts" by Fengru Ge et al. follows the classic model for this type of material (Research Article), comprises four parts: Introduction, Materials and Methods, Results and Discussion, and Conclusions. The list of bibliographic references is adequate; the documentation is appropriate regarding the titles consulted.
The submitted manuscript is undoubtedly progress in the scope of its application.
However, I record here some comments.
Introduction
_The authors should improve the "Introduction" so that the reason for this work is understood. They should show the importance of Isochrysis galbana.
materials and methods
_ In subpoint 2.5, Analytical methods, The various methods presented (line 100 to line 113) should be more detailed. They must also give some important method validation parameters, such as LOD and LOQ.
_ A sub-chapter is missing on the statistical treatment of the data presented.
Results and discussion
_Table 1 must be formatted correctly.
_ Figure 1(A) - The authors should make a comment in the figure and the text about the fact that they do not present in the figure the data relative to the amount of hydrolysates of 0.0 mL L-1
Author Response
Please see the attachment.
Author Response File: 
Author Response.doc
Reviewer 2 Report
The Introduction is very short and does not give a clear picture of DHA production by various microorganisms and substrates. Bellow some recent papers on the problem are listed:
- L. Oliver, L. Fernández-de-Castro , T. Dietrich , M. C. Villaran, R J. Barrio, “Production of Docosahexaenoic Acid and Odd-Chain Fatty Acids by Microalgae Schizochytrium limacinum Grown on Waste-Derived Volatile Fatty Acids”, Appl. Sci., 2022, 12, 3976;
- Y.-Y. Wang, S.-M. Xu, J.-Y. Cao, M.-N. Wu, J.-H. Lin, Ch.-X. Zhou, L. Zhang, H.-B. Zhou, Y.-R. Li, J.-Lin Xu, X.-J. Yan, “Co-cultivation of Isochrysis galbana and Marinobacter sp. can enhance algal growth and docosahexaenoic acid production”, Aquaculture, 2022, 556, 738248;
- F.S. Rohman, M.F. Roslan, D. Muhammad, N.F. Shoparwe, A.A. Hamid, “Multi-objective optimal control of Docosahexaenoic Acid (DHA) production in fed-batch fermentation by Schizochytrium sp.”, Biocatalysis and Agricultural Biotechnology, 2022, 45, 102490;
- K. Khumrangsee, T. Charoenrat, J.Praiboon, et al., ”Development of a fed-batch fermentation with stepwise aeration to enhance docosahexaenoic acid and carotenoid content in Aurantiochytrium sp. FIKU018.”, J Appl Phycol, 2022, 34, 1243–1253;
- F. Gao, I. T. D. Cabanelas, R. H. Wijffels, M. J. Barbosa, “Fucoxanthin and docosahexaenoic acid production by cold-adapted Tisochrysis lutea”, New Biotechnology, 2022, 66, 16–24;
- Zh. Bao, Y. Zhu, Y. Feng, K.Zhang, M. Zhang, Zh. Wang, L. Yu, “Enhancement of lipid accumulation and docosahexaenoic acid synthesis in Schizochytrium sp. H016 by exogenous supplementation of sesamol”, Bioresource Technology, 2022, 345, 126527;
- J. Camacho-Rodríguez, J.J. Gallardo-Rodríguez, M.C. Cerón-García, et al., “A new culture medium based on genetic algorithms for Isochrysis galbana production relevant to hatcheries.” J Appl Phycol, 2021, 33, 3647–3656;
- P. Jakhwal, J. K. Biswas, A. Tiwari, E.E. Kwon, A. Bhatnagar, “Genetic and non-genetic tailoring of microalgae for the enhanced production of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) – A review”, Bioresource Technology, 2022, 344, 126250
The Discussion section should be extended and obtained results compared with those published by other authors for different algae.
p. 1 line 17 – the abbreviation DHA should be explained in the text before first use. Maybe in line 15 – “… and docosahexaenoic acid (DHA) ….”.
p. 2 line 47 – the statement “However, there are few studies about DHA production of I. galbana from starch-rich food processing byproducts” needs citations.
Cited literature in some places redirects to other papers and does not explain the used methods. For example – p2, line 72 – [1]; p. 3 line 103 – [9]; p. 3 line 106 – [12].
In my point of view, it is better to use glucose concentration instead of the quantity of hydrolysate in the text integral.
Data for the changes in biomass concentration with time is missing. This information is quite necessary because lipid production is connected with cell growth and the endpoint of the exponential phase is indispensable for the correct calculation of growth parameters.
In Fig. 1 data for the start of the experiment (t=0) should be given. The authors should comment on the fact that in the first 24 h, a considerable amount of glucose was consumed (about 150 g/l at 200 ml/l hydrolysate and about 75 g/l at 100 ml/l). What are lipid and DHA concentrations at that point? A graphical representation of lipid (and/or DHA) concentration with time will be very informative.
p. 4 line 125 – [16] describes conditions for GS FID fatty acid determination and not for GC-MS –Please give the correct citation.
It is not clear whether there is another carbon source except CO2 in control fermentations.
p. 10 line 266-268 – there is a contradiction between two statements – “The optimal amount of hydrolysates was 50.0 mL L-1 with the highest maximum lipid yield…” and “The culture with 50.0 mL L-1 hydrolysates had the lowest maximum lipid yield of 54.6 mg L-1….”. I suppose the second one is for 0.0 ml/l.
Author Response
Please see the attachment.
Author Response File: Author Response.doc
Round 2
Reviewer 1 Report
I believe the manuscript reviewed by the authors has a high scientific quality and satisfactorily answers all the questions raised. I approve of your publication.
Reviewer 2 Report
I have no more questions or comments
