High-Efficient Production of Cellulosic Ethanol from Corn Fiber Based on the Suitable C5/C6 Co-Fermentation Saccharomyces cerevisiae Strain

Round 1

Reviewer 1 Report

 

The Manuscript describes production of cellulosic ethanol from corn fiber. In the Manuscript Authors describe some variants of pretreatement and detoxification. In the opinion of the Reviewer, the text of the manuscript is written chaotically in some places. Also, not all calculations look correct. It is possible that this is due to the lack of output data. The work contains minor editorial and stylistic errors that do not have a significant impact on the entire manuscript. It is recommended that you read the Guide for Authors carefully.

Why did the Authors not carry out statistical analyses? This would increase the scientific value of the work.

In the opinion of the Reviewer, the description of enzymes should be included in this work.

The Authors did not provide the meaning of all abbreviations, eg what does the abbreviation DCW stand for?

Chemical detoxification is also a form of pre-treatment. For example, alkaline pretreatment affects the decomposition of hemicelluloses. Why was the pH raised to 10? and leaving for 1 hour? The authors did not present the results of measurements of inhibitory substances after all forms of detoxification. In Figure S3, the authors give 5 grams/L of acetic acid, and elsewhere in the article only about 2.5 g/L. What are these differences?

What was the type of alcoholic fermentation used by the Authors?

What is represented on the y-axis in graph 1? And how is it defined?

Why didn't the Authors report the percentage increases in ethanol yield after using different detoxification methods? Figure 4 shows that the profits are not significant, and at times they are worse.

How will the Authors explain the differences between 10% and 20% solid loading? 25 grams of glucose after 12 hours yields 12 grams of alcohol, and 52 grams of glucose yields 22 grams of alcohol. In the opinion of the Reviewer, the differences between the solid loading of the reaction should be discussed more.

How the authors calculated a metabolic rate of 2.2 grams per hour from glucose and xylose. Figure 6 shows that within 6 hours, the glucose concentration decreased from 45 to 15 grams.

What was the theoretical yield of ethanol from glucose and xylose?

And how did the Authors count it? From raw material? or after pre-treatment?

What do the authors mean by total sugar?

How will the authors explain the decrease in ethanol yield with the duration of the process?

In the Reviewer's opinion, Authors did not presented an efficient process route for the production of cellulosic ethanol from corn fiber.

In the opinion of the Reviewer, the chapter on the experiment in the 50L reactor should be more extensive. There are scientific papers on research on alcoholic fermentation on a quarter-technical scale. It would have been worthwhile to have a broader discussion of the alcoholic fermentation process during scale-up.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The article submitted for review presents a summary of a study investigating the use of corn fibre for ethanol production by co-fermentation. Considering the implementation of advanced fuels, I positively assess the study topic choice. The research methodology was well defined and used. The novelty of the study should be clearly pointed out. What was the hypothesis? The paper was well written; however, I find some information missing from the text. My suggestions are given below.
Introduction
This chapter is well written, but I suggest adding information on biological pretreatment methods. These methods do not generate inhibitor formation, which requires detoxification, and are a promising alternative to chemical methods, also due to their costs.
The novelty of the study and the differences with the studies and results of other authors on this topic should be highlighted.
Materials and Methods
Line 149 - Please add the Kjeldahl method before the abbreviation KN.
Line 171 - "...glucose..." in lower case.
Subsection 2.6 - Please complete the description with the amount of hydrolysate. The small amount of oxygen allowing lipid synthesis in the cell membrane improves yeast tolerance to ethanol. Was this the intention of aeration? Please complete the description.

Results and Discussion
- I suggest transferring figures S1-S3 to the main text of the paper.
Line 391 - "...zang..." - should be written with a capital letter.
- Line 412-414 "We speculate that the increased inhibitors affected the strain growth and xylose metabolism due to the increment in solid loading." Did the authors observe yeast cells? Wasn't the reduced yeast growth due to osmotic stress at high carbohydrate content? Please try to explain this.
Line 428 - The date (2022) should be removed.
Figure 6 - Please describe the reasons for the extended glucose utilisation.
Line 460 - "...duplicates.” or, as elsewhere, triplicates?
Conclusions
One of the biggest problems in developing cellulosic ethanol production is the cost of the technology, including the necessary pretreatment and hydrolysis costs. In addition, there are the problems described by the authors resulting from the accumulation of inhibitors, which requires detoxification. The lignocellulosic feedstock management scheme presented in this paper is a multi-step process. Will the high ethanol yield compensate for the time and cost of the chemicals used?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Despite not fully taking into account the Reviewer's comments and incompletely correct answers to the Reviewer's questions, the Authors improved their manuscript to a significant extent.