Conversion of Whey into Value-Added Products through Fermentation and Membrane Fractionation

Round 1

Reviewer 1 Report

The manuscript ‘Conversion of whey into value-added products through fermentation and membrane fractionation’ refers to a very interesting topic but I think that in the current form of the manuscript should not be published in the Water. The main comments are presented below.

The abstract section should be corrected:

• What does this RO sub-item mean?

The Introduction section should be corrected:

• The Introduction section should be implemented with some the latest references about widely application of membrane filtration.

In the Materials and Methods section should be corrected:

• The characteristics of the UF and RO membranes should be written in the text, because it’s not appropriate to create tables with the characteristics of individual membranes.
• Please explain, why these type of UF and RO membranes were used in experiments?
• How parameters (pressures, flow, temperature) were used during individual membrane processes? Why these?
• How determined of maximum Volumetric Concentration Factor?
• The analytical method should be added to this section.

In the Results section should be corrected:

• Please correct of fig.4, descriptions of the x and y axes should be added.
• An abbreviation of ‘Volumetric Concentration Factor’ is VCF, not FCV!
• Please correct of fig.5 and fig.6, the results should be presented in form of ‘Permeate flux vs. VCF’ (without process time, which depends on the membranes area).
• Please correct of fig.7 and fig.8, the results should be presented in form of ‘TMP vs. VCF’ (without process time and permeate flux).

Please update the references. It is necessary to include the most recent literature reports in the manuscript.

After taking into account the comments the article should be reassessed.

Author Response

Firstly thanks so much to the reviewer for the kind approval of this manuscirpt for revision and interesting comments which have improved very much our paper.

Comments and Suggestions for Authors

The manuscript ‘Conversion of whey into value-added products through fermentation and membrane fractionation’ refers to a very interesting topic but I think that in the current form of the manuscript should not be published in the Water. The main comments are presented below.

The abstract section should be corrected:

• What does this RO sub-item mean?

This has been corrected in the manuscript

The Introduction section should be corrected:

• The Introduction section should be implemented with some the latest references about widely application of membrane filtration.

This has been modified in the manuscript

In the Materials and Methods section should be corrected:

• The characteristics of the UF and RO membranes should be written in the text, because it’s not appropriate to create tables with the characteristics of individual membranes.

This has been explained in the manuscript

• Please explain, why these type of UF and RO membranes were used in experiments?

This has been explained in the manuscript

• How parameters (pressures, flow, temperature) were used during individual membrane processes? Why these?

This has been detailed in the manuscript

• How determined of maximum Volumetric Concentration Factor?

This has been detailed in the manuscript

• The analytical method should be added to this section.

This has been completed in the manuscript.

In the Results section should be corrected:

• Please correct of fig.4, descriptions of the x and y axes should be added.

This has been corrected in the manuscript

• An abbreviation of ‘Volumetric Concentration Factor’ is VCF, not FCV!

This has been corrected in the manuscript.

• Please correct of fig.5 and fig.6, the results should be presented in form of ‘Permeate flux vs. VCF’ (without process time, which depends on the membranes area).

This has been modified in the manuscript.  

• Please correct of fig.7 and fig.8, the results should be presented in form of ‘TMP vs. VCF’ (without process time and permeate flux).

This has been modified in the manuscript.  

Please update the references. It is necessary to include the most recent literature reports in the manuscript.

References has been updated with more recent literature reports

After taking into account the comments the article should be reassessed

Author Response File: Author Response.docx

Reviewer 2 Report

In this study, an integrated membrane system consisting of a ceramic ultrafiltration membrane followed by a polymeric reverse osmosis membrane was employed in order to fractionate the fermentation products of cheese whey. In general, this is a quite interesting topic and it falls in the scope of the journal. However, in the reviewer opinion, there are serious concerns about amount of the experimental work described in this paper. More specifically, the fermentation process of whey is already described in detail in a previous publication by the same authors (Cabellero, et al., 2019), while membranes’ behavior during only limited filtration tests  is described here in order to be used as proof of concept.  As a result, in my opinion, this paper could not be accepted for publication in Water in the current form. However, the topic is very interesting, therefore authors are suggested to conduct some additional experiments in the attempt to optimize the separation method and resubmit their work.

Author Response

Firstly thanks so much to the reviewer for the kind approval of this manuscirpt for revision and interesting comments which have improved very much our paper. 

Comments from the reviewer and reply.

In this study, an integrated membrane system consisting of a ceramic ultrafiltration membrane followed by a polymeric reverse osmosis membrane was employed in order to fractionate the fermentation products of cheese whey. In general, this is a quite interesting topic and it falls in the scope of the journal. However, in the reviewer opinion, there are serious concerns about amount of the experimental work described in this paper. More specifically, the fermentation process of whey is already described in detail in a previous publication by the same authors (Cabellero, et al., 2019), while membranes’ behavior during only limited filtration tests is described here in order to be used as proof of concept. As a result, in my opinion, this paper could not be accepted for publication in Water in the current form. However, the topic is very interesting, therefore authors are suggested to conduct some additional experiments in the attempt to optimize the separation method and resubmit their work.

We agree that the fermentation process is described in our previous publication (Caballero et al., 2019). Additionally, in this article it is described the fractionation of the fermented product using microfiltration and esterification-distillation technologies to obtain 4 valuable products: bacterial biomass, a protein hydrolysate, minerals and lactic acid. The different products were also functionally evaluated, showing their potencies as agronomic biostimulants.

In this work, the process has been modified obviating the chemical treatment of esterification-distillation. This is a more simple process, that includes a single solid-liquid fractionation that allows the recovery of water. Fermented product was submitted only to filtration technology, ultrafiltration and reverse osmosis, to obtain 3 products, water, an insoluble concentrate consisting of biomass of Lactobacillus and a soluble biostimulant concentrate. This technology has been tested at a pilot level. It has been demonstrated its effectiveness in solving the main challenges related to obtaining commercial agronomic and animal feed products: stability and transport. In this way, we think that this work would serve to provide a new technological and economically viable approach to the management of whey, by obtaining products with high added value for agronomic and animal food fields.

Author Response File: Author Response.docx

Reviewer 3 Report

The abstract needs to be revised, the paragraph listed as one needs to merge with the abstract,

You mentioned in the introduction "35 kg BOD and 68 kg of COD", this is not right, they do not add, BOD is equal to 1.XX multiplied by the COD.

If using membrane technology then it is much cheaper and effective if used on the raw Whey? use the concentrate to produce biogas or treated in wastewater treatment plants.

This process is impractical and uneconomical, can not have any commercial application?

It is not clear how the fermentation adding anything to the final product, lack of research in this area?

Please justify and answer the questions/comments above and add to the context of the article. 

What are the current technologies/methods used to treat/utilise this by-product?

 

 

Author Response

Firstly thanks so much to the reviewer for the kind approval of this manuscirpt for revision and interesting comments which have improved very much our paper. 

Comments from the reviewer and reply.

The abstract needs to be revised, the paragraph listed as one needs to merge with the abstract,

This has been corrected in the manuscript

You mentioned in the introduction "35 kg BOD and 68 kg of COD", this is not right, they do not add, BOD is equal to 1.XX multiplied by the COD.

There is no mathematical relation between BOD and COD in any case. Normally is used the relation between BOD and COD as a reference value to know the biodegradability of the effluent to be treated, but there is not a fixed relation.

In addition, BOD is contained in the COD, therefore BOD value must be lower than COD.

Nevertheless, values have been updated with a more recent reference.

If using membrane technology then it is much cheaper and effective if used on the raw Whey? use the concentrate to produce biogas or treated in wastewater treatment plants.

Raw whey is a waste with little application, with a high water content, and a low bioavailability of its carbohidrated. Fermented whey is a product with high added value. Fermentation is the key point in this process, turning a poor by-product into a high-value product. Biostimulant / bioprotective products obtained in this process have an added value and a much higher demand in the market.

The solution proposed by reviwer 3 would be, from our point of view, wasting a by-product with an interesting nutritional profile that can be used in an economically and technologically feasible way in the production of biostimulant and bioprotective agronomic products.

Additionally, most of the small / medium cheese industries do not generate enough whey volumes to implement and maintain a biogas production plant, and the low productions of this biogas would force to burn this product, without being able to be used as a source of usable energy.

This process is impractical and uneconomical, can not have any commercial application?

The process converts whey into high value-added products. Thus, generated products compensate the expenses derived from its implementation, even generating benefits. The technology described has been implemented at demonstrative scale. The AGR-212 research group of the Universidad de Sevilla own production plants of 1 - 8 m³, and has transferred part of the know-how of this technology to various companies in the agronomic biotechnology sector. Currently the agronomic interest of this product has already been evaluated with positive results at the field level.

It is not clear how the fermentation adding anything to the final product, lack of research in this area?

Fermentation is the key point in this process converting a poor by-product, whey, into a high value added product with biostimulant capacity and application in animal feed.
It is fully demonstrated, from the agronomic point of view, that the fermented product obtained has a high biostimulant potential. Although not published, results at the field level as result of the transfer of this technology to private sector, also support this statement.

Additionally, probiotics are widely used in animal feed, and their implication in improving production yield is widely described.

Please justify and answer the questions/comments above and add to the context of the article.

What are the current technologies/methods used to treat/utilise this by-product?

Responding to this suggestion, the introduction has been expanded including a paragraph detailing the different current alternatives for managing cheese whey.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I suggests publishing the manuscript ‘Conversion of whey into value-added products through fermentation and membrane fractionation’ after considering the comments below:

The Introduction section should be implemented with some references about application of nanofiltration in dairy industry, e.g.:

1. Z. Chena, J. Luoa, X. Hanga, Y. Wan, Physicochemical characterization of tight nanofiltration membranes for dairy wastewater treatment, Journal of Membrane Science 547 (2018) 51-63.
2. A. Kowalik-Klimczak, E. Stanisławek, Reclamation of water from dairy wastewater using polymeric nanofiltration membranes, Desalination and Water Treatment 128 (2018) 364-371.

In the Results section should be corrected:

• Please correct of fig.5 and fig.6, should be used ‘permeate flux’ instead of ‘flux’ both on the y axes and in figures caption.
• Please correct of fig.5, fig.6, fig.7 and fig.8, it necessary to remove the legend from these figures.

Author Response

Firstly thanks so much again to the reviewer for the kind approval of this manuscirpt for revision and interesting comments which have improved very much our paper.

 Comments and Suggestions for Authors

I suggests publishing the manuscript ‘Conversion of whey into value-added products through fermentation and membrane fractionation’ after considering the comments below:

The Introduction section should be implemented with some references about application of nanofiltration in dairy industry, e.g.:

1. Z. Chena, J. Luoa, X. Hanga, Y. Wan, Physicochemical characterization of tight nanofiltration membranes for dairy wastewater treatment, Journal of Membrane Science 547 (2018) 51-63.
2. A. Kowalik-Klimczak, E. Stanisławek, Reclamation of water from dairy wastewater using polymeric nanofiltration membranes, Desalination and Water Treatment 128 (2018) 364-371.

Ok. This has been included in the introduction.

In the Results section should be corrected:

• Please correct of fig.5 and fig.6, should be used ‘permeate flux’ instead of ‘flux’ both on the y axes and in figures caption.
• Please correct of fig.5, fig.6, fig.7 and fig.8, it necessary to remove the legend from these figures

You are right, thanks. These two corrections have been done.

Author Response File: Author Response.docx

Reviewer 2 Report

 

After carefully reading of both revised manuscript and author’s response to the reviewers, it is considered that authors have successfully addressed the concerns raised by the reviewer and therefore, this paper can be  published in Water.

My only concern has to do with the membrane process employed in this experimental work. In the abstract, it is argued that a microfiltration membrane was used as a first stage of separation. On the contrary, an ultrafiltration membrane is described in the rest of the paper. Please make the necessary corrections.

 

Author Response

Firstly thanks so much again to the reviewer for the kind approval of this manuscirpt for revision and interesting comments which have improved very much our paper.

Comments and Suggestions for Authors

After carefully reading of both revised manuscript and author’s response to the reviewers, it is considered that authors have successfully addressed the concerns raised by the reviewer and therefore, this paper can be  published in Water.

My only concern has to do with the membrane process employed in this experimental work. In the abstract, it is argued that a microfiltration membrane was used as a first stage of separation. On the contrary, an ultrafiltration membrane is described in the rest of the paper. Please make the necessary corrections

You are right, thanks. This has been corrected.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors has addressed most of the reviewer's comments

Author Response

Thanks so much again to the reviewer for the kind approval of this manuscirpt for revision and interesting comments which have improved very much our paper.