Kluyveromyces marxianus: Current State of Omics Studies, Strain Improvement Strategy and Potential Industrial Implementation
Round 1
Reviewer 1 Report
Manuscript ID: Fermentation_1010459
Manuscript Title: Kluyveromyces marxianus: Current state of Omics studies, strain improvement strategy and potential industrial implementation
Comments to authors:
- Crabtree effect is an important effect related to this review and authors had a passing reference in the abstract but after that authors never mentioned crabtree-effect. I want authors to add a paragraph on crab-tree effect and how any yeast like organism behave when the external glucose conc. exceed any threshold limit (more than 150 mg/L), how the organism switch to accelerated glycolysis, how the need for oxygen is depleted and how the alcoholic fermentation occurs. This phenomenon is critical for this review and authors have not provided any plausible and detailed account on this. Please discuss this in the light of Kluyveromyces marxianus species.
- thermocellum when used for the first time (Line 197), please expand and subsequent mention can be abbreviated.
- On page 9,authors have mentioned about using CRISPER-Cas9 genome editing technology and heterologous expression system for improving ethanol productivity but authors also mentioned that these techniques are not very well established. I recently came across an excellent review on how chemicals can be used for improving lipid production in microalgae and the authors of that review talks about several chemicals that can be specifically used to target specific enzymes (see https://www.sciencedirect.com/science/article/pii/S0163782718300195). Perhaps some of the molecules mentioned in that review article can be a route to selectively target certain enzymes and try to improve the ethanol production. Author should also try such strategies if the CRISPER or RNAi technology are difficult. Because this chemical genetics approach doesn’t rely on genome editing and strains that are difficult to manipulate can be induced for desirable characters. There are some excellent reviews on chemical genetics, please see https://nph.onlinelibrary.wiley.com/doi/full/10.1111/j.1469-8137.2009.03045.x
https://www.frontiersin.org/articles/10.3389/fpls.2012.00309/full
http://www.plantphysiol.org/content/174/1/5.short
- Overall, the review is nicely written and it covers most of the topics that pertains to the genetically improvement of bioethanol/ biobutanol in K. marxianus.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The present work is up to date and interesting since it reviews the potential of Kluyveromyces marxianus yeast strains as alternative to the widely spread use of S. cerevisiae for industrial ethanol production.
Overall, the authors give an excellent insight into previous works reporting the application of Omics technologies to develop industrially relevant K. marxianus strains and their application under different process configurations for bioethanol production.
Indeed, I just have one relevant comment to be addressed to improve the manuscript. The authors should review the erroneous use of the term productivity throughout the text once the authors exhibit concentration values, instead of productivity, to support the relevance of the yeasts. As alternative, the authors might support the discussion throughout the manuscript in the productivities achieved for the different strains evaluated since this is really an industrially relevant parameter.
Providing the authors address this comment, to my opinion the manuscript might be acceptable for publication.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
