Abstract

A reader reported complained about errors in the original paper, which was sent to the authors. The authors responded to the complaint but did not submit a corrigendum. To provide a balanced view, the written documents of both, the reader (reporter) and the author, are presented here; Reporterâ�� comments. In this study, the differences between the features of exopolysaccharides produced by two different bacteria L. Plantarum and P. Pentosaceus were investigated. According to the results in Table 2, these polysaccharides have different molecular weights, and percentages of protein and polysaccharides. However, it is not clear why FTIR spectra of these two polysaccharides have only slight differences in the identified peak wave numbers (indicated in the image per case). In other words, the â��peak sizeâ��, â��the ratio of peak sizeâ�� and â��peaksâ�� locationsâ��, in both of the exopolysaccharide produced by L. Plantarum and P. Pentosaceus are quite similar. While, according to Table 2, it is expected that the transmittance of the samples be quite different in the specific range of proteins and polysaccharides. Hence, it seems that one of the spectrums was prepared by editing the other spectrum using a graphical software. Author's response: For FT-IR characterization of EPS, both samples were sent to a specified laboratory in Ferdowsi University of Mashhad where the analysis was performed using FT-IR spectrophotometer (Thermo Scientific Nicolet 6700, Avatar 370 FT-IR, USA). The data, Exel files and the spectrums generated by that laboratory are attached as a supplement to this report to show the invalidity of the claim against us regarding the edition of spectrums by a graphical software! By observing the data (which are inserted to the following table for review) and the overlay graph on the attached Excel file (Supplement 1), slight differences can be observed. However, the functional groups present in isolated EPS including hydroxyl, carboxylic acid and ester groups with DPPH radical scavenging activity are found similar in both EPS samples. None of the referees from LWT put any comment against these results and trends. Table presented Reporter's analysis of author's response: It is very unlikely that wavelengths and peak intensities in FTIR transient diagrams of two EPSs with different concentrations of protein and polysaccharide, which were obtained from two different bacterial genera, to be exactly the same. In the following, we will elaborate to support our claims with scientific references. A) Transmittance has an exponential relation with the concentration. According to Beer-Lambert Law, the relation between transmittance and the sample concentration is obtained from this equation: Table presented T = transmittance (relative amount of light passing through a sample) I, I0 = intensity (Wm-2) of transmitted and incident radiation, respectively Iµ = molar absorptivity (m2molâ��1 or Mâ��1cmâ��1) or how strongly a chemical species absorbs light at a given wavelength b = path length (distance light travels through the chemical species) c = molar concentration of chemical species A = absorbance (relative amount of light absorbed by sample)Each change in the concentration of materials and consequently the concentration of functional groups and bonds will lead to an exponential change in the FTIR spectrum. Therefore, considering the concentration of compounds mentioned in the paper and the Beer-Lambert equation, the ratio of the transmittance difference shown in the FTIR diagram for protein and polysaccharide-related functional groups between EPS obtained from Lactobacillus and Pediococcus should be exponentially higher than the ratio of the differences between their concentrations. Considering these issues, the difference between the transmittance of the samples, according to the table presented in the authors' responses, is negligible compared to the differences between the protein and polysaccharide concentrations as presented in Table 2. Figure presented B) According to Shang, Xu, and Li and Smith, the range of EPS fingerprint is between 900 and 1200 cmâ��1. However, the authors introduced this range between 500 and 1300 cmâ��1 without citing any references. Also, none of the peaks in the table provided by the authors in their answers are in this range.C) According to Sigma-Aldrich IR spectrum database, Smith, Helm and Shao, the characteristic peak of the proteins in EPS is observed at 1580â��1650 cmâ��1. In the table provided by the authors in their answers, the difference between the transmittance of EPSs obtained from Lactobacillus and Pediococcus is negligible, in contrast to their protein concentration that is significantly different.D) The difference in material composition leads to shifting the peaks of functional groups to higher or lower wavelength and shifting a peak of less than 10 cmâ��1 is usually meaningless. Therefore, according to the FTIR diagram, peaks were not shifted that does not make sense. © 2020 Elsevier Ltd

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