Pilot Scale for Production and Purification of Lactic Acid from Ceratonia siliqua L. (Carob) Bagasse
Round 1
Reviewer 1 Report
In this work, pilot scale for production and purification of lactic acid from Ceratonia siliqua L. (Carob) bagasse was presented. The manuscript is well prepared, however, few queries should be addressed, before considering it for publication:
1) Starting in the abstract section, I would suggest to write out the »hours« instead writing just »h«, as sometimes it is written with space, other times without space. Such unit should be written out and corrected throughout entire manuscript. Same with liters (»L«), as sometimes it is used with space, other times without. Should be unified (space or no space before L?). Unify.
2) I would also suggest writting units in form of »g/g« instead of using dots, as in »g∙g−1«. To be corrected throughout the whole manuscript. To be corrected with all units, that are written in such manner.
3) Line 87-89: It should be pointed out, which main components were determined.
4) Figure 1 is of really bad quality, also, tab marks are still visible in the figure. The figure should be replaced.
5) Figure 2 should be divided in two separate figures, if possible.
6) Line 196: correct »ca«
7) Line 205-208: Figure 3 caption is written in different font sizes. Correct. Also, Figure 3 should be divided in two separate figures, if possible. Axis y title: units with dots, not clearly presented. Use g/L form, as mentioned before.
8) Figure 4: It should be pointed out somewhere in the manuscript, that nkjel stands for determination of total nitrogen by Kjeldahl. Maybe consider it in line 219-220.
9) There are a lot of abbreviations, that are not explained in the manuscript (UF, NF, MF, ...). Should be clear to the reader what you are suggesting. Please consider while revising.
10) Figure 5 caption: remove the excess dot at the end of caption.
11) Line 282: delete excess spaces between “average production”. There are actually more of such unnecessary spaces throughout the whole manuscript. Should be revised.
12) The manuscript should be proofread by an English native speaker, as there are also a lot of punctuation marks missing (commas), which make the manuscript hard to read.
Considering these minor changes to the manuscript, it think the overall research work was adequately performed and can be considered for publication in journal Fermenatation.
Author Response
The point-by-point response to the reviewer’s # 1 comments is attached.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this work, the authors studied the production of lactic acid using Carob biomass as feedstock and a thermophilic Bacillus coagulans isolate cultivated in a batch pilot scale of 35L fermenters without yeast extract supplementation and operated for 50 h.
It is not very original, but it can be interesting to widen the potential raw material source usable for the fermentation to lactic acid.
Before the publication, some aspects need minor revisions, such as:
- Introduction: the final aim of the work is not described clearly.
- Introduction: the industrial application of this study isn’t clear. Authors have to deepen the potential industrial applications of their research. First with specific bibliography analysis about the industrial needs of the research section of the work, then describing the final purpose of the work done, in terms of industrial application;
- Introduction: nothing potential alternative to fermentation to lactic acid of 2nd generation sugars was cited in the paper, an example can consist in the BDO production (De Bari, I., Giuliano, A., Petrone, M.T., Stoppiello, G., Fatta, V., Giardi, C., Razza, F., Novelli, A., 2020. From cardoon lignocellulosic biomass to bio-1,4 butanediol: An integrated biorefinery model. Processes 8, 1–18. https://doi.org/10.3390/pr8121585). Addi t;
- Conclusions: conclusions are poor, describe the results obtained and how the current lactic acid production systems can improve.
- Conclusion: the research can be interesting, but the application of this study isn’t clear. Authors have to deepen the potential industrial applications of their research;
- In general, the authors should describe the advantages of the adopted approach and obtained results also considering the potential environmental/economic improvement.
Author Response
The point-by-point response to the reviewer’s # 2 comments is attached.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper was foused on an interesting aspect related to the bioconversion of biomass into lactic acid. Few revisions are required and they are reported below:
- I suggest to add a nomencalture list to explain all acronyms and parameters with the proper unit of measure
- figure 1 should be revised
- check that all details for the instruments used and reported in section 2 are added to the manuscript
- please add references for the PLA production
- I suggest to include more details for the purification of LA produced
- being an experimental study I suggest to add a section for the uncertainity analysis, the variation bars should be added to the figures and tables found in the results achieved
Author Response
The point-by-point response to the reviewer’s # 3 comments is attached.
Author Response File: Author Response.pdf
Reviewer 4 Report
The presented article is devoted to the bioconversion of Carob (Ceratonia siliqua L.) biomass to the lactic acid by thermophilic Bacillus coagulans isolate in a pilot scale reactor. High purity of the resulting lactic acid (99.9%, w/w) was achieved by using a cascade of different purification stages. Without any doubt, the article will be of interest for the readers of Fermentation.
I think that the article can be improved taking into account the following comments and suggestions:
- There is practically no discussion in the article, but it would be useful to briefly discuss such an issue. The use of multi-stage purification increases the purity, but at the same time leads to an increase in the cost of the product. How many stages of purification is it advisable to have in order for the product to have a reasonable price? Is this criterion fulfilled in this work?
- All data in the article are given in concentrations, with the exception of Fig.4, which shows masses. It may be appropriate to recalculate these data in concentration?
- In the abstract, it is necessary to write that it is almost optically pure L-lactic acid.
-In Figure 1, unnecessary signs must be removed.
Author Response
The point-by-point response to the reviewer’s # 4 comments is attached.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The paper was extensively revised.
