Development of 2,3-Butanediol Production Process from Klebsiella aerogenes ATCC 29007 Using Extracted Sugars of Chlorella pyrenoidosa and Biodiesel-Derived Crude Glycerol

Round 1

Reviewer 1 Report

Article entitled “Development of 2,3‐butaendiol production process from Klebsiella aerogenes ATCC 29007 using extracted sugars of Chlorella pyrenoidosa and biodiesel‐derived crude glycerol” by Lee et al. The major strength of the article is the CCRD statistics analysis used for 2,3 BDO fermentation and the use of algal extracts and crude glycerol as a biorefinery perspective. Eventhough the approach used is good but more experimental studies and clear explanation of text in the article would have made the study more interesting.

Authors mention in the title and in the article, the use of extracted sugars of Chlorella pyrenoidosa for the production of 2,3-BDO. Only algal sugars glucose and galactose were mentioned in the article as involved in 2,3-BDO production. It would be relevant to show the composition of different sugars in algal extract and how they impact the production of 2,3-BDO. Otherwise the title and statement has to be modified accordingly.

Lines 164-166 and Lines 207-208: The statement “In the 2,3 BDO production process using chemical sugars, glucose consumed all sugar for 0 to 6h and galactose consumed all sugar for 18 h” looks very strange. How can a sugar consume sugar?

Lines 199-201: Authors mention that “According to previous reports, K. aerogenes ATCC 29007 at a concentration was 40 g/L or more had a substrate inhibition effect by crude glycerol.” It’s not clear whether the concentration 40g/L is K.aerogenes or crude glycerol? In addition, there is no reference to support this statement. It would be relevant to provide either a reference or experimental result to further support the claim.

Line 204: 84% what does percentage indicates, whether it is w/w or v/v?

Page 7: Fig 2A: Authors show that highest conversion rate for 2,3 BDO is at 10 g/L, but there is no trend in the conversion rate or yield of 2,3-BDO with increase in concentration of crude glycerol. 2,3 BDO yield seems to decrease at 20g/L and increased at 30g/L of crude glycerol concentration. Checking at concentration higher than 30g/L of crude glycerol concentration might be better to know whether there is improvement in the yield of 2,3BDO.

Line 274: casein hydrolysate “centration” should be corrected  

Line 291-293: The statement “The 2,3‐BDO production was not significantly affected by the variables at either the lowest casein hydrolysate concentration or the lowest casein hydrolysate concentration.” should be corrected.

Page 11: Conclusions stated by the authors are not clear. Statements are confusing, and does not show what actually authors want to mention to conclude the study. Conclusion section need to be rewritten clearly to clarify the statements.

Author Response

Thank you so much for the detailed review. Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

For this research paper, the authors investigated the optimum condition of 2,3-BDO productin using Klebsiella aerogenes ATCC 29007 with extracted algal sugar and also optimized the medium compositions using statistical method. In my opinion, this work is too simple to be accepted as a research paper. The only fermentation optimization and CCRD experimantal design can only be considered as an experimental report while not a research paper. Meanwhile, the this manuscript is also lack of innovation. Thus, I do not recommend this paper to be accepted. 

Author Response

Thank you so much for the detailed review. Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper presents a deep experimental study that is dedicated to optimizing process conditions improving 2,3-BDO production. The statistical tools are clearly defined. The experiments and their results are professionally described. Nevertheless, I miss the following information.

1) Add please information about the experimental error, i.e. standard deviations at least.

2) The technical set-up description for used experimental apparatuses is missing, like extraction vessels, mixed reactors, and heaters. Just analytical tools are commented.

3) It was hard to understand the process itself in the first look. I recommend to present it as the block diagram with inputs/outputs/energy input and recovery. It will improve the clearness of the manuscript.

4) I miss the base information about the process - energy demand of your technology, prices for applied chemicals, purity of your product, basic economic balance, scale-up limits, TRL level of your proposal. Can you please add brief information to the discussion?

Author Response

Thank you so much for the detailed review. Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Reviewer 3 Report

The revised paper got a higher rank due to its clearness and deep presentation. I have no other comments. Congratulation to the authors, really good paper.