Production of xylanase by Aspergillus niger GIO and Bacillus megaterium through solid-state fermentation

  1. Samuel Adedayo Fasiku
  2. Mobolaji Akeem Bello
  3. Olubusola Ayoola Odeniyi

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Abstract

Xylanase breaks xylan down to xylose, which is used in industries such as pulp and paper, food and feed, among others. The utilization of wastes for xylanase production is economical, hence this work aimed at producing xylanase through solid-state fermentation and characterizing the enzyme. Xylanase-producing strains of Bacillus megaterium and Aspergillus niger GIO were inoculated separately in a 5 and 10 day solid fermentation study on maize straw, rice straw, sawdust, corn cob, sugarcane bagasse, conifer litters, alkaline-pretreated maize straw (APM) and combined alkaline and biological-pretreated maize straw, respectively. The best substrate was selected for xylanase production. The crude enzyme was extracted from the fermentation medium and xylanase activity was characterized using parameters such as temperature, cations, pH and surfactants. Among different substrates, the highest xylanase activity of 3.18 U ml −1 was recorded when A. niger GIO was grown on APM. The xylanase produced by A. niger GIO and B. megaterium had the highest activities (3.67 U ml −1 and 3.36 U ml −1 ) at 40 °C after 30 and 45 min of incubation, respectively. Optimal xylanase activities (4.58 and 3.58 U ml −1 ) of A. niger GIO and B. megaterium , respectively, were observed at pH 5.0 and 6.2. All cations used enhanced xylanase activities except magnesium ion. Sodium dodecyl sulfate supported the highest xylanase activity of 6.13 and 6.90 U ml −1 for A. niger GIO and B. megaterium , respectively. High yields of xylanase were obtained from A. niger GIO and B. megaterium cultivated on APM. The xylanase activities were affected by pH, temperature, surfactants and cations.

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  1. Version published to 10.1099/acmi.0.000506.v5 on Access Microbiology
  3. Version published to 10.1099/acmi.0.000506.v4 on Access Microbiology
  5. Access Microbiology

    Comments to Author

    The manuscript is improved, however, there are still some minor amendments needed to the figures. There are error bars in figures, however, you don't say what the error bars are made from. Standard deviation? Standard error of the mean? Are there any significances to add to figure 3? All figure legends should provide enough information about the figure that a figure could be understood if the figure was removed from the manuscript and displayed alone. You need to add a lot more information into the legends at the moment without repeating too much of the main text. This is the same for tables. You need to define the elemental symbols in figure 4

    Please rate the manuscript for methodological rigour

    Satisfactory

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  6. Version published to 10.1099/acmi.0.000506.v3 on Access Microbiology
  8. Access Microbiology

    Comments to Author

    The authors present a compelling manuscript, indicating the capacity of Aspergillus Niger Gio And Bacillus Megaterium to degrade xylan from waste sources, that without management contribute to environmental pollution. They also present and methodical approch for characterisation of enzymatic activity of xylanase, which can be applied as resource for other studies examining enzymatic activity.

    Please rate the manuscript for methodological rigour

    Very good

    Please rate the quality of the presentation and structure of the manuscript

    Good

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  9. Access Microbiology

    Comments to Author

    1. Methodological rigour, reproducibility and availability of underlying data 2. Presentation of results 3. How the style and organization of the paper communicates and represents key findings 4. Literature analysis or discussion 5. Any other relevant comments

    Please rate the manuscript for methodological rigour

    Good

    Please rate the quality of the presentation and structure of the manuscript

    Good

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  10. Access Microbiology

    Comments to Author

    Thank you for submitting the revised manuscript. However, the responses to reviews comments and how they have been addressed is insufficient to convince me that this revision is an improvement. Therefore, previous comments of reviews need to be address again and responded to properly. There are some further points that now need to be addressed (in addition to the previous round of comments). Line 79 - circular plugs or square plugs? What shape were the plugs? Lines 98 to 100 aren't needed and subheadings 2.4.1, 2.4.2, and 2.4.3 can be amended Not enough detail in section 2.5 Significance needs to be shown on Figure 2 as well as in the text. Also, more analysis of the data is needed in the whole results section. Figure legend for figure 2 needs more information. Significance needs to be displayed on figure 4. The figure 4 legend needs more information. Line 233 - this is a redundant statement. Line 252 doesn't make sense. Lines 270 to 275 requires more critical evaluation regarding the effects of EDTA. Line 280 - 'some bacteria'. What are the species? Name them. Are they comparable to what you've done? Your statement is too generic.

    Please rate the manuscript for methodological rigour

    Satisfactory

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  11. Version published to 10.1099/acmi.0.000506.v1 on Access Microbiology
  12. Version published to 10.1099/acmi.0.000506.v2 on Access Microbiology
  14. Access Microbiology

    Comments to Author

    The manuscript is bit confusing due many experiments on impact of environmental and nutritional factors on xylanase production and activity. The authors may streamline the manuscript and may elaborate on mechanism and mode of action of these factors on activity or production for eg surfactants, temperature etc. The application of two different types of xylanase and their activity also needs elucidation. The tables should be self explanatory. Typographical errors may be avoided

    Please rate the manuscript for methodological rigour

    Satisfactory

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  15. Access Microbiology

    Comments to Author

    1. Methodological rigour, reproducibility and availability of underlying data: (a) Seems to be good. The authors have touched upon different factors influencing enzyme activity (b) The identity of bacteria has not been disclosed. Was it characterized and identified? If yes, then it must be mentioned. If not, then it must be characterized. Simply reporting as Bacillus spp. doesn't make sense (c) It would have been good if the authors also quantified the amount of xylanase produced by the microbes. This would have implications on the commercialization potential of these microbes. 2. Presentation of results: The results could be presented in a more visually appealing form. Use of graphs to represent the data would help the reader in understanding and analyzing the data better. 3. How the style and organization of the paper communicates and represents key findings: Overall looks good 4. Literature analysis or discussion: Very few papers have been referred to for the discussion section. The authors should include a paragraph on how the xylanase activity reported in this paper compares against those extracted from other Aspergillus and Bacillus strains. Or how this xylanase compares to those isolated from other sources. 5. Any other relevant comments: (a) In Line 128, Plate 1 should be replaced with Figure 1, and the same should be mentioned in lines 125 and 126. (b) The Conclusion section needs to be revised for grammatical errors (279) and lack of coherence (277, 282, 283).

    Please rate the manuscript for methodological rigour

    Good

    Please rate the quality of the presentation and structure of the manuscript

    Good

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  16. Access Microbiology

    Comments to Author

    The manuscript is generally well referenced and well written. There are a few areas that need attention for the correction of English grammar. I would suggest a native English speaker proof read the article before resubmission. Line 63 - remove 'poured into petri dishes and allowed to cool', you don't need to tell the reader how to pour agar Section 2.1 - a figure would be helpful here Line 82 - do not provide centrifuge speeds in rpm. rpm is different for every centrifuge. Prove the speeds in factors of g or rcf. An alternative is to provide the make and model, including rotor size, of the centrifuge you used so the reader can make the conversion from rpm to rcf. Line 87 - what was the acetate buffer made from? or has this been purchased? Line 93 - 'micromole', keep units consistent. You haven't written the units out anywhere else in the manuscript Line 98 - remove the first sentence. This is just repeating the heading Line 98 - 'About'. Did you use 0.5ml or didn't you. 'About' is not accurate, reproducible or scientific. Other example of this is line 104 Line 104 - remove the first sentence. It is repeating the heading Plate 1 and intext reference - this should always be called a figure never a plate Line 222 - you say there are many researchers but only provide a single reference. If you say 'many' you should be providing at least 5 references for that statement Line 266 - this is not the first time you have mentioned EDTA, however, this is the first time you have defined what it stands for. The first time EDTA is mentioned is where you should define what it stands for.

    Please rate the manuscript for methodological rigour

    Good

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes