From Agricultural Wastes to Fermentation Nutrients: A Case Study of 2,3-Butanediol Production
, Victor Chinomso Ujor 3, Hasan K. Atiyeh 4, Ifeanyi Iloba 1, Nasib Qureshi 5,† and Thaddeus Chukwuemeka Ezeji 1,*Round 1
Reviewer 1 Report
The article examines the production of 2,3-butanediol from agricultural wastes such as anaerobic digestate and biochars.
The authors develop several fermentation strategies and make very interesting and valuable calculations of the economic effect of the processes.
In general, the article is well organized, the results are credible, and the conclusions are well-argued. I have one question for the authors: do they have any idea about the contents of the anaerobic digestate? What amount of nitrogen and carbon should be expected in it?
I also have the following few remarks:
Supplementary tables should be moved to the main text of the manuscript. They contain very important information and must be in front of the reader so that the work can be appreciated.
Table 1 is too far removed from its first mention to be moved further up in the text.
Figure 1 - it is very small. Give a legend to a, b and c.
The designations of all figures with letters, e.g. Fig. 2 and all others: give the letters in the legend, for example: "The concentrations of aluminum, barium, calcium, cobalt, copper, iron, magnesium, nickel, phosphorus, ammonia, and nitrate (А-К)". Also, in the MDPI style, the letters should be lowercase.
Fig. 2S - on the abscissa is gL instead of g/L
All references should be revised according to the journal's requirements and links should be added.
Ref. 8: Okonkwo et al. (2017a) - no need for "a".
Author Response
Reviewer 1
Comments and Suggestions for Authors
The article examines the production of 2,3-butanediol from agricultural wastes such as anaerobic digestate and biochars.
The authors develop several fermentation strategies and make very interesting and valuable calculations of the economic effect of the processes.
Comment 1: In general, the article is well organized, the results are credible, and the conclusions are well-argued. I have one question for the authors: do they have any idea about the contents of the anaerobic digestate? What amount of nitrogen and carbon should be expected in it?
Response: We appreciate the reviewer’s questions regarding the content of anaerobic digestate. The content of anaerobic digestate varies depending on the source of the raw materials from which the digestate is derived. Anaerobic digestate typically contains little to no carbon, as the carbon has been converted into carbon dioxide and methane (biogas) during the anaerobic digestion process. The digestate from anaerobic digestion of organic feedstocks such as animal manure, municipal waste and industrial wastewater are rich in ammonia, nitrogen, phosphorus, heavy metals, and some unidentified chemical components that can affect the growth of microorganisms. The total nitrogen and phosphorus content of the anaerobic digestate used in this study ranges from 1000 to 2000 mg/L, and 2500 to 3000 mg/L, respectively. A statement to this effect has been added to the revised manuscript. See page 3, lines 102 – 103.
I also have the following few remarks:
Comment 2: Supplementary tables should be moved to the main text of the manuscript. They contain very important information and must be in front of the reader so that the work can be appreciated.
Response: Supplementary Tables S1, S2, S3, and S4 have been moved to the main manuscript and are now Tables 2, 10, 8, and 9, respectively.
Comment 3: Table 1 is too far removed from its first mention to be moved further up in the text.
Response: Table 1 has been moved very close to where it was first mentioned in the manuscript (see line 120, p.3).
Comment 4: Figure 1 - it is very small. Give a legend to a, b and c.
Response: Figure 1 in the manuscript has been slightly enlarged and the legend changed from uppercase to lowercase.
Comment 5: The designations of all figures with letters, e.g. Fig. 2 and all others: give the letters in the legend, for example: "The concentrations of aluminum, barium, calcium, cobalt, copper, iron, magnesium, nickel, phosphorus, ammonia, and nitrate (А-К)". Also, in the MDPI style, the letters should be lowercase.
Response: The figure legends in the manuscript have been revised to conform to the MDPI style. The uppercase letters in all the figure legends of the manuscript have been changed to lowercase.
Comment 6: Fig. 2S - on the abscissa is gL instead of g/L
Response: The ‘gL’ of the abscissa of Fig. 2S has been changed to ‘g/L’ in the supplementary materials.
Comment 7: All references should be revised according to the journal's requirements and links should be added.
Response: We added journal doi links to all the references in the manuscript (See lines 557-669).
Comment 8: Ref. 8: Okonkwo et al. (2017a) - no need for "a".
Response: The letter ‘a’ after ‘2017’ in Ref. 8 in the manuscript has been removed (See Line 574 and 576, p. 17).
Reviewer 2 Report
This manuscript is well written and discussed, and definitely adds value to the current literature on the bio-processing of animal wastes with an accent on the production of 2, 3-butanediol. I only have few suggestions, including:
- An emphasis on the motivation and the relevance of the production of 2, 3 -BD compared to other alternatives in the introduction
- A more thorough economic analysis and impact of the production of 2, 3-BD, besides the production cost evaluation and the provision of an estimate of the production capacity.
Author Response
Reviewer 2
Comments and Suggestions for Authors
This manuscript is well written and discussed, and definitely adds value to the current literature on the bio-processing of animal wastes with an accent on the production of 2, 3-butanediol. I only have few suggestions, including:
Comment 1: - An emphasis on the motivation and the relevance of the production of 2, 3 -BD compared to other alternatives in the introduction
Response: We appreciate the reviewer’s comments and we have included some texts illustrating the motivation and relevance of 2,3-BD production alternatives in the introductory section of the main manuscript. Please see lines 64-70 in the main manuscript for details.
Comment 2: - A more thorough economic analysis and impact of the production of 2, 3-BD, besides the production cost evaluation and the provision of an estimate of the production capacity.
Response: The manuscript has been revised to include a detailed discussion of economic analysis and impact of 2,3-BD production. Please see Lines 516-528, p. 16 in the main manuscript.
Author Response File: 
Author Response.pdf
