Bio-Succinic Acid Production from Palm Oil Mill Effluent Using Enterococcus gallinarum with Sequential Purification of Biogas

Round 1

Reviewer 1 Report

he manuscript optimizes the production of succinic acid from POME and explores the process coupled with CO2 removal from biogas, resulting in an interesting approach for the reduction of CO2 emissions. The manuscript is well organized and well discussed, the ways and means are well described and results are properly statistically analyzed. However, some points need attention before being published:

·       A strong English revision is necessary

·       Please add a flowchart of the proposed palm oil mill industry containing succinic acid and biogas coproduction

·       Line 94: please provide centrifugation conditions in xg

·       Item 2.3: Please provide reference for medium supplementation

·       Table 1: it is not clear why there is no a Key factor represented by the letter “I”

·       Item 2.6: please provide a reference for biogas production protocol

·       Item 2.7: it is not clear how purified biogas was captured and how methane purity was measured after biogas mediated succinic acid production

·       Table 6: please set clear the level of confidence considered in the data analysis

Author Response

Q1: A strong English revision is necessary

Respond: Thank you so much for your suggestion. We have revised English and tried to improve it.

Q2: Please add a flowchart of the proposed palm oil mill industry containing succinic acid and biogas coproduction

Respond: Thank you so much for your suggestion. We have added Graphical representation in manuscript. We have drawn it in the way where it can explain simultaneous production of biogas and bio-succinic acid from POME (page 3).

Q3: Line 94: please provide centrifugation conditions in xg

Respond: Thank you so much for your suggestion. Centrifuge speed with g force is provided on page 3 line 100.

Q4: Item 2.3: Please provide reference for medium supplementation

Respond: Thank you for your reminder. Appropriate reference is added in the content on page 3 line 117.

Q5: Table 1: it is not clear why there is no a Key factor represented by the letter “I”

Respond: Thank you for your comment. We used design expert software for optimization of significant factors affect succinic acid production, wherein this software does not show “I” letter to represent any factor.

Q6: Item 2.6: please provide a reference for biogas production protocol

Respond: Thank you for your reminder. The biogas production protocol was developed by our previous work, which was not published.  We add more detail for the biogas production on page 4 lines 150-153.

Q7: Item 2.7: it is not clear how purified biogas was captured and how methane purity was measured after biogas mediated succinic acid production

Respond: Thank you for your comment. The statement is added to clarify how was methane measured for biogas purification (page 5 lines 165-168).

Q8: Table 6: please set clear the level of confidence considered in the data analysis

Respond: Thank you for your comment. The level of confidence is added in the footnote below Table 6 (page 10).

Reviewer 2 Report

The paper focuses on the production of succinic acid from palm oil mill effluent by Enterococcus gallinarum, without substrate pretreatment. The paper brings practical knowledge on the topic. It is well written.

My specific comments are:

Abstract, lines 22-23: „It was reported that MgCO3 and peptone were the most important factors.”. This sentence should be written more detailed. It is not clear in what respect they are important factors.

Introduction, line 65: Abbreviation TCA should be expanded.

Results and discussion, lines 176-183: Scientific discussion to explain that 2-fold dilution was more effective than no dilution and 5-fold dilution should be added.

I recommend minor revision of the paper.

Author Response

Q1: Abstract, lines 22-23: It was reported that MgCO3 and peptone were the most important factors.” This sentence should be written more detailed. It is not clear in what respect they are important factors.

Respond: Thank you for your suggestion. The sentence on lines 23–24 is revised to clarify the statement.

Q2: Introduction, line 65: Abbreviation TCA should be expanded.

Respond: As suggested by Reviewer 2, the full name of TCA is presented on page 2 line 67.

Q3: Results and discussion, lines 176-183: Scientific discussion to explain that 2-fold dilution was more effective than no dilution and 5-fold dilution should be added.

Respond: Thank you for your suggestion. As per reviewer 2 suggestion we have added detail scientific discussion on page 5 lines 190-194.