Identification, Quantification and Kinetic Study of Carotenoids and Lipids in Rhodotorula toruloides CBS 14 Cultivated on Wheat Straw Hydrolysate

Round 1

Reviewer 1 Report

 

Title: Identification and quantification of carotenoids and lipids in Rhodotorula toruloides CBS 14 and their kinetics during cultivation on wheat straw hydrolysate

 

In this manuscript, the purpose of the author was to investigate the production of carotenoids and lipids by Rhodotorula toruloides CBS14, cultivated on wheat straw hydrolysate. An ultra-high-performance liquid chromatography (UHPLC) method was developed and validated, to quantify the different carotenoids produced. Saponification effects on individual carotenoid quantification were identified. The significance of this article is not explained clearly, and there is no strong logic between the research contents. Moreover, the authors should revise the manuscript for language. Overall, I don't think the manuscript is suitable for publication.

 

 

Specific comments

 

1. Pay attention to part preparing your manuscript of the journal, the Abstract should not exceed 200 words.

 

2. The significance of this study is not clear, not innovative

 

 

3. Nonstandard writing, such as determining optical density (L147) and cell dry weight.

Author Response

General: We asked a native speaker, our colleague associate professor Su-Lin Hedén for language correction

Comment 1: Thank you for the advice, we have now shortened the Abstract to less than 200 words.

Comment 2: We regret that the innovative character of this manuscript did not become clear. We would like to emphasize that this study has a pioneering character in several ways. At first, many studies use saponification in carotenoid analysis, without taking into account its effects onto the outcome of the analytics. Our study is the first one in yeasts (as expressed in 3.1.3). We are also the first following the kinetics of an oleaginous yeasts in forming carotenoids and different lipid classes in lignocellulose hydrolysate. Finally, we discovered a substantial amount of free fatty acids. Although this confirms earlier results from us, it is a remarkable finding, since this amount would be regarded toxic for non- oleaginous yeasts. So, we think there is some innovation in the study.

Comment 3: We have corrected this example and looked in general over the language (see general comment above), hopefully it is acceptable now.

Reviewer 2 Report

1.      1. I feel that the authors should reconsider the title of this manuscript. The authors developed and validated an analytical method for the determination of carotenoids and analyzed the composition of cell biomass during the batch process. However, the current title gives the impression that the manuscript is focused on the determination of carotenoids and lipids during cultivation.

2.     2. Please check and correct grammar mistakes. e.g. Line 31: „triacylglycerides (TAGs) was the major…“

3.      3. Figure 2. During the last 24 hours of cultivation, cell and biomass concentration increased significantly (by ~5 and 4 g/L, respectively). The concentration of consumed sugars (xylose and glucose) was ~ 4 g/L+ 4 g/L, meaning that lipid yield YL/S was ~0.5 g/g. The theoretical lipid yields YL/S for glucose and xylose are 0.31 and  0.34 g/g, respectively. Please explain and discuss the lipid synthesis and biomass growth during this period.

4.      4. Please discuss the changes in carotenoid and lipid class composition as well as lipid and carotenoid content during the batch growth and tie them to the physiology of the cell.

5.      5. Table 4. The space between the second, third and fourth columns should be adjusted.

 

 

Author Response

Comment 1: Thank you for the advice. We have now modified the title to "Identification, quantification and kinetic study of carotenoids and lipids in Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate"

Comment 2: We now edited the text with the help of a native speaker (assoc prof Su-Lin Hedén) and hope that we managed to correct all grammar mistakes.

Comment 3: Thank you for sharing this observation (we have to admit that we overlooked this). There is some discussion in the oleaginous yeast community that those yeasts are accumulating intracellular polysaccharides, which are later converted to lipids. This might be the reason here, although this needs to be verified. We added an according statement (paragraph 3.2.1).

Comment 4: We added some comments about the possible physiological functions of the lipid classes and carotenoids (paragraphs 3.2.2 and 3.2.3).

Comment 5: Changed accordingly.

Reviewer 3 Report

The authors in their original research article presented the development and validation of the method for accurate quantification of carotenoid pigments produced by Rhodotorula toruloides CBS14, which was cultivated on wheat straw hydrolysate. UHPLC and spectrophotometric methods were applied in the study, and saponified and unsaponified samples were compared also. Furthermore, the kinetics of carotenoids and lipids biosynthesis was also evaluated.

In my humble opinion, the manuscript has been prepared correctly, and all of the sections are sufficient. The methodology part has been adequately described, as well as, the results are clearly presented and supported by a very good discussion.

I have only two minor suggestions:

- It is not necessary to write the reference numbers in the superscripts.

- Please, add more space between the values of fatty acids content in Table 4, because at the moment these values are illegible.

Author Response

Thank you for the positive feedback.

• References were put in brackets
• Table 4 was corrected accordingly.