Enhancement of Biomethane Yield from Spent Mushroom Substrate: Biological Pretreatment with the Chlamydospores of Trichoderma viride

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article received for review is very interesting. The authors presented the results of research on the possibility of increasing the amount of biogas produced by pretreatment the substrate using a biological method. The introduction is interesting and explains the need to conduct research, the results of which are presented in the article. The methodology was presented in a very detailed manner. The graphic side is of a high standard. The drawings are legible and explain the obtained results well. However, Chapter 4 leaves a certain dissatisfaction. It seems to me that much more conclusions can be drawn from such a number of results. Please also include a few comments and questions in the final version of the article:

1. Line 120 - why was the experiment ended after 40 days. Was any criterion adopted?
2. Line 180 - -1 should be in the superscript
3. Line 181 - something is wrong with the Rmax unit
4. Subsection 2.6.1 - why were two models used?
5. Figure 5 is a bit illegible.
6. It seems to me that captions should be under the figures.
7. I suggest splitting Figure 6 into two figures. There is too much content there at the moment.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript by Zhu et al. investigates the effect of chlamydospore pretreatment of spent mushroom substrate on subsequent biomethane yield. The implementation and enhancement of anaerobic digestion to meet renewable energy goals is currently a hot topic and therefore this study is worthy of further investigation. Although its novelty is rather limited, the manuscript offers interesting information for readers of Fermentation. However, the text contains many spelling and grammatical mistakes to be found in the text. For these reasons, the reviewer suggests extensive revision and strongly encourages proofreading by a native English speaker. My comments are listed below.

• “Trichoderma viride” should be italicized. Please go through the manuscript and adjust.
• Line 36 should be “annual output”.
• Line 37-39: please add a reference.
• How is SMS currently managed? What are its disposal strategies?
• Line 47-48: please critically compare the advantages and disadvantages of this method. Currently only the advantages are mentioned. Could long treatment times be a disadvantage compared to other pretreatment methods?
• Sometimes lignocellulose is used, and sometimes ligno-cellulose. Please be consistent.
• Line 55-57: please add a reference.
• Line 59: “in-vestigation” should be investigation.
• Line 68: grammatical error.
• Line 91: “8” should be in superscript?
• Hypsiygus marmoreus, Auricularia polytricha and Auricularia auricular should be italicized.
• The authors mention the characteristics of both SMS and used inoculum. How were these parameters determined? The analytical procedures for these parameters are missing. Please elaborate. In 2.4 the authors give – very briefly – some additional information. However, can the authors give more details. This can also be provided in supplementary information.
• Line 108: “5” should be in superscript?
• Line 116: “days” should be “day”.
• Line 139: is there a “/” too much in the ideal gas constant?
• Please add the units of the parameters that are used in the equations.
• Line 164: space is missing
• Line 180: “-1” should be in superscript?
• Line 181 why is there a “-“ in mL/g VS-d ?
• From the results it is clear that treating SMS with Tv for longer than 48h is not beneficial (lower cumulative methane yield). The authors give the following explanation in Lines 267-270: “It indicated that the pretreated SMS lower than 48 h contained abundant substances that can be rapidly converted into methane, while with a longer pretreatment duration than 48 h, these readily convertible substances were consumption by Tv instead of by anaerobic microbes.” Is this a hypothesis or a confirmed statement? If this is a statement, how is this experimentally determined (i.e., which readily convertible substances are measured for tv < 48 h).
• Table2: Please reformat so that all content that should be on a single line remains on a single line..
• Line 288-289: referencing error.
• Line 306-308: >1500 mg/L TAN is already sufficient to cause ammonia inhibition. What do the authors consider inhibitory in this case? Please support by a reference.
• Line 308: grammatical error.
• Please italicize Penicillium, Aspergillus and Apiotrichum.
• Please italicize Fermentimonas, Syntrophomonas and other species names.
• Line 393: please mind the subscripts in chemical formulas.
• Figure 5 is somewhat difficult to read. Is it possible to improve its quality for better quality? Likewise Figure 6a and 6b, is it possible to increase font size here?
• Line 468: please mind the subscripts in chemical formulas.
• Line 506-508: “The increased cost of Tv pretreatment based on this study is 66.7 CNY per 1000 kg SMS (20 CNY per 500 mL Tv chlamydospores solution).”, does this cost make sense in an industrial setting?
• Line 534: “ini-tial” should be “initial”.

Comments on the Quality of English Language

Please see comments above.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors addressed most of the reviewer's comments, and therefore, the reviewer accepts this manuscript for publication in Fermentation.