Effect of Elevated Oxygen Concentration on the Yeast Yarrowia lipolytica for the Production of γ-Decalactones in Solid State Fermentation
Round 1
Reviewer 1 Report
The manuscript is interesting, describing the effect of elevated oxygen concentration on the Yarrowia lipolytica growth and production of metabolites through solid-state fermentation process.
The document has a high similarity index (79%), due to the same information has been included in a PhD these published in 2018. (https://theses.hal.science/tel-01830160/document?).
I see no problem with this, since it is the thesis work of one of the authors of the manuscript. However, 5 years have passed since then. From all references, 84 % are older than 10 years, and 30 % are self-citations. So, it is necessary to carry out a bibliographic search in search of similar works to expand and update the discussion of the results.
The format of references it is not according to the guide for authors.
Line 21: Replace “(at 0 h and 20 h)” by “(at 0 and 20 h)”
Line 23: Replace “(at 0 h, 20 h, 35 h, 48 h and 60 h)” by “(at 0, 20, 35, 48 and 60 h)”
Line 75: Replace “….1 cm by 1 cm by 0.5 cm” by “1x1x0.5 cm”.
Line 90: Replace “..at 0 h and 20 h and ii) injection at 0 h, 20 h, 35 h, 48 h and 60 h” by “at 0 and 20 h and ii) injection at 0, 20, 35, 48 and 60 h)”.
Authors use a gas analyzer to estimate the oxygen and carbon dioxide content during the bioprocess. Then, the biomass estimation was expressed in terms of cell concentration, according to previous study (Try et al. 2018). However, in previous study only report the biomass estimation by counting the extracted cells in a Malassez chamber, and no correlation is shown. How was this correlation, what was its fit value? Why no report the biomass estimation in terms of carbon dioxide production?
Line 126: Replace “Logistic differential equation (1) was use to estimate growth kinetics and logistic differential equation (2) was used to estimate oxygen consumption and lactone kinetics….:” by “Logistic differential equation was use to estimate growth kinetics (Eq.1) as well as oxygen consumption and lactone kinetics (Eq. 2).
Line 147: Replace “20 % and 50 %” by “20 and 50 %”.
Fig. 3. Why not shown the data adjusted to logistic model?
Table 1. Put the missing letters according to Fisher´s test.
Line 175: “… the model fitted relatively well…” Which was the value??
Table 2. Why not shown the data adjusted to logistic model?
Figure 5. Data showed have a high value of error bars, which complicates the interpretation and discussion of the results. Adjust the range of “x” axis according to the time of sampling.
Line 212: “….with a relatively good fit…” Indicate the value.
Line 214: Authors reported that “Specific production rates of dec-3-en-4-olide in the condition of 30 % oxygen ratio reached a higher value compared to other conditions…”; However, in table 3, the value at this condition has not significant differences with the other treatments. Check this sentence and correct it.
Author Response
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Author Response.pdf
Reviewer 2 Report
Though the manuscript is written in a good flow I doubt in the methodology and content whether only concentration of oxygen is a good enough subject to study in this aspect.
SSF is a sensitive technology and detail must be provided in methodology and must be discussed in introduction also. I would like authors to highlight more that how this study is different from others existing ones.
Section 2.2: 6th line 'containing' must be 'contained'
How the work is different and superior from that of Try S, et al., 2018?
Conclusions must be written more precisely.
Author Response
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Reviewer 3 Report
1. Figure 1.
Instead of “MITOCHONDRIE” should be “ MITOCHONDRION”.
2. Please describe in detail how the samples were withdrawn during cultivation and how they were analysed (results are presented in Figures 3-5.)
3. Line 135.
The authors should describe how the specific production rates of g-decalactones and specific oxygen consumption rates were calculated.
4. Table 1.
The authors should first calculate the growth rates from growth curves, i.e. exponential growth phase by:
A) Graphical derivation of the curve µ =(dX/dt)*(1/X)
B) numerically based on linearised exponential equation X=Xo*e(µ*t)
Then based on the determined specific growth rates chosen mathematical model can be applied, and constants like maximal specific growth rate could be accurately determined.
5. A logistic equation would be useful if the growth of cells is limited with available space on an inert solid support (e.g. when the cells grow in a monolayer). However, in this experiment, authors studied the effect of oxygen concentration on cell growth and the production rate of g-decalactone. Therefore, the equation for cell growth should relate the oxygen concentration to cell concentration and product accumulation. Next, the maximal specific growth rate is characteristic of the organism grown on a specific source under chosen conditions (e.g. pH, T, mixing, other sources need for cell growth, etc.) (Table 1.) The maximal specific growth rate is constant and doesn’t change with the concentration of the studied substrate, in this case, oxygen. The same applies to the maximal specific oxygen consumption rate and maximal specific production rate of different g-decalactone (Table 3.). Please correct accordingly.
6.
Unfortunately, the authors didn’t provide data on carbon source concentration (castor oil+Tween 80) which is of great importance when the kinetics of cell growth is analysed. Figure 4 shows that cells intensively grow as long as oxygen is still available. Based on the presented results, it can be assumed that cell growth stops when oxygen is consumed, and the carbon source doesn’t affect it (concentration above limiting concentration). Therefore, carbon source concentration would be needed to confirm the previously mentioned assumption.
Author Response
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