Cited by 104Spectroscopy Techniques in Biomedical and Chemical ResearchAlgal biology and biofuel productionSpectroscopy and Chemometric Analyses

The DOI matches its Crossref record; 50 of the 50 references it cites were found in a registry or an index; none of the 45 sources its claims cite is checked for support yet.

Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis

Open access
C. Esther Elizabeth Grace, P. Kiruthika Lakshmi, S. Meenakshi, Vaidyanathan, Seetharaman, S. Srisudha, M. Briget Mary·2020·Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Abstract

Fourier transform infrared (FTIR) and Raman spectroscopic techniques were employed to analyze the biomolecular transitions and lipid accumulation in three freshwater green microalgal species, Monoraphidium contortum (M. contortum), Pseudomuriella sp. and Chlamydomonas sp. during various phases of their growth. Biomolecular transitions and lipid [hydrocarbons, triacylglycerides (TAGs)] accumulation within the microalgal cells were identified using second derivatives of the FTIR absorption spectroscopy. Second derivative analysis normalized and resolved the original spectra and led to the identification of smaller, overlapping bands. Both relative and absolute content of lipids were determined using the integrated band area. M. contortum exhibited higher accumulation of lipids than the other two species. The integrated band area of the vibrations from saturated (SFA) and unsaturated lipids (UFA) enabled quantification of fatty acids. The percentage of SFA and UFA was determined using GC, FTIR and Raman spectroscopy. From the spectral data, the order of increasing concentration of SFA among the three microalgal species was M. contortum > Chlamydomonas sp. >Pseudomuriella sp. The spectral results on fatty acids were consistent with the separation of lipids by gas chromatography. The results emphasized the significance of FTIR and Raman spectroscopic methods in monitoring the biomolecular transitions and rapid quantification of lipids, without the need for extraction of lipids.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

FTIR and Raman spectroscopy with second-derivative analysis tracked biomolecular transitions and lipid accumulation in three freshwater green microalgae across growth phases, with *M. contortum* accumulating the most lipids/TAGs. Spectral SFA estimates were consistent with GC separation, supporting rapid, extraction-free lipid quantification.

Key findings

  • *M. contortum* showed higher lipid accumulation (hydrocarbons and TAGs) than *Pseudomuriella* sp. and *Chlamydomonas* sp.; its absolute content increased nearly 6-fold for hydrocarbons (0.7 to 3.9) and 13-fold for TAGs (0.2 to 2.6).
  • Relative TAGs:Amide I ratio rose from ~0.5 to 4.3 for *M. contortum* and 3.8 for *Chlamydomonas* sp., a seven- to eight-fold increase during the declining phase compared with *Pseudomuriella* sp.; relative hydrocarbon content increased 2–3 fold by day 40 for all three species.
  • SFA order by FTIR/Raman was *M. contortum* > *Chlamydomonas* sp. > *Pseudomuriella* sp.; FTIR SFA percentages were 93, 83, and 74, and Raman SFA percentages were 80, 75, and 71, respectively. GC showed maximum SFA for *Chlamydomonas* sp., but total SFA+MUFA was high for *M. contortum*; spectral results were consistent with GC separation.

Methods

  • Three freshwater green microalgal isolates were cultured in modified BG11, 300 mL, in triplicates at 27 µmol m−2 s−1, 25±2°C, and 12:12 h light/dark; cells were harvested on days 10, 20, 30, and 40 and freeze-dried.
  • FTIR used KBr pellets (1:100), a Thermo Nicolet 380 spectrometer, 32 scans, 4 cm−1 resolution, 4000–500 cm−1, DTGS detector, yielding 9 spectra per species per phase (108 total). Raman used a Modular 1064 Raman system, 1064 nm laser at 149 mW, 200–3200 cm−1, 10–15 cm−1 resolution, 5 s/10 scans, InGaAs detector (36 spectra total).
  • Spectra were smoothed (Savitzky–Golay), second derivatives were obtained, and integrated band areas were used. Relative lipids were normalized to amide I; absolute lipids were normalized to a zero-intensity spectral region. GC-FID after modified Bligh–Dyer extraction and FAME preparation validated fatty acid percentages.

Limitations

  • No explicit limitations section; the paper does not state limitations.
  • Evident from the text: only three freshwater green microalgal species and one cultivation/growth series were examined; Raman fatty acid quantification and the GC/FTIR/Raman comparison were recorded on day 30 (stationary phase), so broader species or condition generalization is not tested.
  • Evident from the text: relative lipid content depends on amide I normalization, which the authors note changes with growth phase; they address this for absolute content by normalizing to a zero-intensity spectral region.

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Integrity signals

Registry

Crossref · 10.1016/j.saa.2019.117382

Cites

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Verification

Claims the paper makes

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Show all 54 claims

  • It may state two separate claims as one. 22
  • The quote only partly states this claim. 1
  • Probably not a substantial claim. 13
33 of 33
  • The paper relies on this without support.

    The intensity variation in the FTIR spectra reflects absorbance changes proportional to microalgal concentration or cell population, as described by the Beer-Lambert law.

    “The intensity variation in the spectral data represents the change in absorbance which is proportional to the concentration / cell population of the microalgae, according to the Beer Lambert's law.”
  • The paper relies on this without support.

    The region with almost zero intensity in the second derivative spectra does not change with growth phase or species and has no characteristic bands.

    “normalized by a region with almost zero intensity (10 -6 ) in the second derivative spectra, which does not change with the phases of growth as well as with the species and have no characteristic bands”
  • The paper relies on this without support.

    Gas chromatography is a reliable method for fatty acid analysis.

    “Gas chromatography (GC) is one of the conventional methods, widely used as a reliable technique for fatty acid analysis.”
  • The paper relies on this without support.

    Gas chromatography requires extraction of lipids from algal cells.

    “However, the method requires extraction of lipids from algal cells.”
  • The paper relies on this without support.

    Integrated band areas in FTIR and Raman spectra are proportional to the amount of the corresponding lipid component.

    “Relative and absolute lipid contents of the species were calculated using the integrated peak area of the lipid regions.”
5 of 5

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  • GC and spectral analyses identify different species with the most saturated fatty acids

    Major

    GC identifies Chlamydomonas sp. as having the most saturated fatty acids, whereas the stated spectral ranking places M. contortum first. This contradicts the paper's conclusion that the methods give consistent results for saturated fatty acids.

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Citations

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Research works printed but not linked: 2

  1. Stehfest, 2005, vol. 43, 717
  2. Driver, 2015, vol. 11, 148

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Metadata

Authors
Grace, C. E. E., Lakshmi, P. K., Meenakshi, S., Vaidyanathan, S., Srisudha, S., & Mary, M. B.
Affiliations
  • Lady Doak College (IN)
  • University of Sheffield (GB)
Corresponding author
M. Briget Mary
Venue
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Publisher
Elsevier BV
Published
2020-01
Volume
224
Pages
117382
ISSN
1386-1425 (ISSN-L)
OpenAlex
W2957070687
Cited by
104
References
50
Citations by year
2026: 9 · 2025: 10 · 2024: 27 · 2023: 14 · 2022: 13 · 2021: 23 · 2020: 7
FWCI
5.17
Type
journal article
Language
en
Open access
Locations
  • Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy (publishedVersion)
  • PubMed (publishedVersion)
  • White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
Funders
  • Biotechnology and Biological Sciences Research Council
  • Department of Biotechnology , Ministry of Science and Technology
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biophysics › Spectroscopy Techniques in Biomedical and Chemical Research
  • Physical Sciences › Energy › Renewable Energy, Sustainability and the Environment › Algal biology and biofuel production
  • Physical Sciences › Chemistry › Analytical Chemistry › Spectroscopy and Chemometric Analyses
Keywords
green microalgae, lipid accumulation, Monoraphidium contortum, Chlamydomonas, triglycerides, fatty acid composition, saturated and unsaturated fatty acids, lipid quantification
MeSH terms
Chlorophyta, Fatty Acids, Lipids, Spectrum Analysis, Raman, Spectroscopy, Fourier Transform Infrared, Biofuels, Microalgae

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