Fermentative L-Lactic Acid Production Using Bacillus coagulans from Corn Stalk Deconstructed by an Anaerobic Microbial Community
, Zhiyuan Shi, Tongyu Wang, Xiangyu Meng, Lili Song, Zhiping Zhang, Jingnan Zhang and Tao Wei *
Alejandro Téllez-Jurado
Round 1
Reviewer 1 Report
The work overviews the silage process and subsequent fermentation using B. coagulans. In the paper, you can improve your presentation. I am sending the observations resulting from the review.
Observations
Lines 84-86. The determination of the composition of the raw material that is described was carried out in the present work. If so, they are results and should go in the corresponding section.
Lines 88-92. How did you identify the strains? Is there a previous job? If so, the strains' sequences must be deposited in a database such as a GenBank.
Line 113. What is the origin of cellulase?
In the results section, only the results should be described, and references should not be placed as the authors do; the references should go into discussing the results. The description of the results needs to be clarified with the discussion. For example, in lines 207-213, the presence of lignin is being discussed.
Figure 2. Trying to include the values of the times in the graph.
Table 1. Table footer, what parentheses?
To complement the studies, conducting a functional analysis study would be convenient to strengthen the observed results.
Lines 359-370. In summary, the authors mention the yield of g of lactic acid per g of raw material. The methodology needs to say how they obtained the yield; this data does not appear in the results. Please review it.
Lines 382-384. After silage, is the resulting substrate subjected to sterilization before adding the Bacillus? If not, what could you comment on the biota present, and how can it interfere with fermentation with B. coagulans?
The discussion is very short; if you add all the information described in the results, you would have a broader discussion. Another option is to combine the results section with the discussion and generate a single one as results and Discussion (if the journal format allows it).
No comment
Author Response
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Reviewer 2 Report
Manuscript: „Fermentative L-lactic acid production using Bacillus coagulans, from corn stalk deconstructed by an anaerobic microbial community“
Xu Yang, Zhiyuan Shi, Tongyu Wang, Xiangyu Meng, Lili Song, Zhiping Zhang, Jingnan Zhang, Tao Wei
The research is a very innovative and encompasses many tasks associated with industrial biotechnology, microbiology, environmental technology, and bio-economy. Conversion of lignocellulose biomass into high value-added products is a very important task. This research analyzed the possibilities of producing L-lactic acid from dry corn stalk (DCS) that was pretreated by ensiling by an anaerobic microbial community consisting of Bacillus coagulans, Lactobacillus fermentum, and Enterococcus durans. The maximal concentration of lactic acid reached 18.54 ± 0.52 g/L with substrate concentration 5%, the yield of lactic acid was 0.31 ± 0.01 g/g DCS, and the optical purity of the product lactic acid was >97%.
Comments and suggestions to the authors:
1) The authors should correct (g/100 g dry matter) in 237 paragraph.
2) I suppose, that should be written the title of table in the Figure 1.
3) To correct the quality of the view of Figure 1 of the table.
4) The authors should correct (10 FPU g−1 cellulose) in 113 paragraph.
5) The authors should correct 250 mL in 114 paragraph.
6) The authors should correct 5 L in 126 paragraph.
7) The authors should correct 100 mL in 146 paragraph.
8) The authors should correct the quality of the view of the Figure 5.
9) The authors should correct (0.22 μm) in 161 paragraph.
Comments for author File: Comments.pdf
Author Response
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Reviewer 3 Report
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The manuscript entitled “Fermentative L-lactic acid production using Bacillus coagulans, from corn stalk deconstructed by an anaerobic microbial community” is interesting for the scientific community. The manuscript presentation is clear and it has interesting pictures which allow a better understanding of the role of the synthetic community of three lactic acid bacteria in the anaerobic ensiling process of dray corn stalk. |
The resolution of Figure 3 is very poor. Please increase the size of this figure.
Did the authors check during the fermentation process (DCS1-DCS7) the abundance and diversity of genes encoding carbohydrate-active enzymes?
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Author Response
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Reviewer 4 Report
1. Lines 95-129. Did the authors wash and dry microsilage or use wet biomass prior enzyme hydrolysis and fermentation? How was the microsilage stored until use? Was the microsilage autoclaved prior to enzyme hydrolysis and fermentation? Please add these information to Materials and Methods (subsection 2.2.-2.4.)
2. Line 121: SSCF Please write the full name and after, write the abbreviation in brackets.
3. When writing the abbreviation the first time, put the full name in brackets afterwards. Please add the full name of the abbreviation.
4. Figure 2; according to legend, should be presented concentrations of lactic and acetic acid and xylose as well as pH at specified times (7th, 14th, 21st, 28th, 35th, and 42nd day of cultivation). However, in the figure are presented four curves for microsilages (DCS1-DCS7) (see x-axis). On the left y-axis is presented the concentration of lactic acid and on the left y-axis pH. Authors should add on the y-axis concentration of acetic acid and xylose. Next, they should add data for each specified sampling time and each biomass (original and pretreated). It would be convenient to have a diagram for each pretreated and original biomass with concentrations of lactic and acetic acid and xylose as well as pH at specified times for the 7th, 14th, 21st, 28th, 35th, and 42nd days of cultivation.
5. Figure 5a is too small to read and hardly readable. The authors should consider enlarging the size of the figure and improving its resolution. Next, acetic acid, xylose and cellobiose concentrations should be added to y-axis legend.
6. Figure 5a. Authors should consider writing „enzyme prehydrolsis“ in the figure for the processing time between 0 and 48 hours.
7. Figure 5a. Was the concentration of LA at the beginning of the process 0 g/L? The concentration of the LA in DCS4 was cca. 2 g/L, according to Figure 2.
8. The Discussion section should be improved. The authors should critically compare their results with relevant studies in the literature and give recommendations for future research in order to improve LA concentration and productivity of the process.
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