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Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis
Open accessAbstract
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.
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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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45 Own result · 20 Not checked yet · 11 Own interpretation · 8 Own method · 3 Partly supported · accuracy not yet measured
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In the paper
“The smaller bands at ~3008 cm -1 ν (= C-H) and ~ 1270 cm -1 (= C-H) were due to the stretching and bending vibrations of unsaturated fatty acids in the algal lipids.[21,26,50].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.1. Second derivative analysis on each species at their various growth phases:
What the sources say
- Not checked yetcites [21]
- Partly supportedcites [26] sourceExperimental — accuracy not yet measured
In Results and Discussion, under “Second derivative analysis of the FTIR yeast spectra in the lipid absorption regions” (page not supplied), the paper assigns a band around 3,009 cm−1 to =CH stretching typical of unsaturated fatty acids. It does not assign a band around 1,270 cm−1 to =CH bending, and its spectral measurements concern oleaginous yeasts rather than algal lipids. (LLM, conf=0.88)
- Not checked yetcites [50] source
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In the paper
“Thus the intensity variation observed in the spectra due to biomolecular transitions can be attributed to the metabolism of cells during their various phases of growth [26,28].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.1. Second derivative analysis on each species at their various growth phases:
What the sources say
- Supportedcites [26] source
The Results and Discussion section reports changes in FTIR band intensities during yeast growth and says these changes might reflect cell metabolism. Its second-derivative analysis likewise describes spectral variations as likely reflecting metabolic changes accompanying growth. The claim's “can be attributed” is consistent with that qualified interpretation. (LLM, conf=0.88)
- Partly supportedcites [28] sourceExperimental — accuracy not yet measured
The Results and Discussion report changes in infrared peak intensities associated with proteoglycans and other cartilage components. But those changes were examined after enzymatic removal of proteoglycans; the paper does not attribute them to cell metabolism during growth phases. Page numbers are unavailable in our copy. (LLM, conf=0.83)
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- Rests on an assumption: The intensity variation in the FTIR spectra reflects absorbance changes proportional to microalgal concentration or cell population, as described by the Beer-Lambert law.
- Supported
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In the paper
“The characteristic vibrations of lipid unsaturation are (=C-H) at ~3008 cm -1 , (C=C) at ~1655 cm -1 and (=C-H) at ~1270 cm -1 [21,34,50].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.2. Raman spectral analysis on the lipid accumulation in green microalgal species
What the sources say
- Not checked yetcites [21]
- Partly supportedcites [34] sourceExperimental — accuracy not yet measured
The “Fatty acids and fats” section (p. 10) identifies a C=C stretching band at 1655 cm⁻¹ in unsaturated fatty acids and associates a band at 1265 cm⁻¹ with =C–H deformation as double-bond content changes. The passages do not establish the claimed =C–H vibration at approximately 3008 cm⁻¹; a search for that band found no supporting passage in our copy. (LLM, conf=0.88)
- Not checked yetcites [50] source
plaincorrelational- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“However, this band was observed as a very weak band in Pseudomuriella sp., and Chlamydomonas sp. (Fig. 3).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
plain- Asserted: passes — The authors put it forward as true.
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In the paper
“Two characteristic bands of the amide groups of protein chains, amide I and amide II were observed at ~1653cm -1 and ~1550 cm -1 respectively.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1. FTIR analyses on the biomolecular transitions and lipid accumulation
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In the paper
“However, from the 20 th day to the 40th day of growth, drastic changes in the spectral intensity of the three species were observed (Fig. 4b).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
plaincorrelational- Asserted: passes — The authors put it forward as true.
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In the paper
“The bands observed in the region 3050 to 2800 cm -1 corresponds to ν(CH 3 ) and ν(CH 2 ) asymmetric and symmetric stretches of hydrocarbons from lipids”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1. FTIR analyses on the biomolecular transitions and lipid accumulation
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In the paper
“The region between 1250cm -1 and 1000 cm -1 was due to ν(C-O) stretches of polysaccharides from carbohydrate and ν(P=O) stretches of phospholipids and nucleic acids (Table 1) [8,[20][21][22]30].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1. FTIR analyses on the biomolecular transitions and lipid accumulation
What the sources say
- Not checked yetcites [8,[20][21][22]30]
plaindirect- Asserted: passes — The authors put it forward as true.
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In the paper
“The band at ~ 3008 cm -1 corresponded to the stretching vibrations ν (= C-H) from the unsaturated fatty acids was clearly visible in M.contortum.(Fig. 4b to Fig. 4d) [21,26].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
What the sources say
- Not checked yetcites [21]
- Not checked yetcites [26] source
boosted- Asserted: passes — The authors put it forward as true.
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In the paper
“the band at ~1745 cm -1 was due to carbonyl stretches from esters of fatty acids, mainly called as triacylglycerides (TAGs).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1. FTIR analyses on the biomolecular transitions and lipid accumulation
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In the paper
“While the intensity of the amide I (~ 1653 cm -1 ) and amide II (~ 1550 cm -1 ) bands of proteins and the carbohydrate bands increased till the stationary phase and decreased in the declining phase.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.1. Second derivative analysis on each species at their various growth phases:
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In the paper
“The raw absorption spectra showed distinct absorption bands corresponding to different biomolecules such as carbohydrates, proteins and lipids over the wave number range 4000 -500 cm -1 .”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1. FTIR analyses on the biomolecular transitions and lipid accumulation
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In the paper
“the position of the bands corresponding to the biomolecules was observed to be almost the same (i.e. in the expected wavenumber range) at every phase of growth, but their intensity varied remarkably.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.1. Second derivative analysis on each species at their various growth phases:
plain- Asserted: passes — The authors put it forward as true.
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In the paper
“Second derivatives resolved the overlapping bands in the raw spectra, removed the baseline errors and lead to the identification of small and adjacent absorption bands and enabled quantitative analysis [26,49].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1. FTIR analyses on the biomolecular transitions and lipid accumulation
plaindirect- Asserted: passes — The authors put it forward as true.
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In the paper
“Bands due to lipids were ~1745cm -1 (C=O), ~1462cm -1 ( as CH 3 ), ~1380cm -1 ( s CH 3 ) and of proteins were ~1658cm -1 (amide I mainly C=O), ~ 1547 cm -1 (amide II N-H, C-N).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
plain- Asserted: passes — The authors put it forward as true.
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A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“M.contortum exhibited nearly 6 fold increase in the hydrocarbons (0.7 to 3.9) and a thirteen fold increase in TAGs (0.2 to 2.6).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Absolute content of lipids:
plaindirectSingle case- Asserted: passes — The authors put it forward as true.
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- Rests on an assumption: The region with almost zero intensity in the second derivative spectra does not change with growth phase or species and has no characteristic bands.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The stretching vibration of =C-H at ~3008 cm -1 was observed for all the three species, with maximum intensity for M.contortum, which was also confirmed in the FTIR spectra (Fig. 2 and Fig. 4).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.2. Raman spectral analysis on the lipid accumulation in green microalgal species
plaincorrelational- Asserted: passes — The authors put it forward as true.
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In the paper
“The percentage of SFA from the Raman spectra was 80 for M.contortum, 75 for Chlamydomonas sp.71 for Colour should be used for this figure in print a) b) c) Fig.10 Fatty acid analysis by a) Gas chromatography b) FTIR and c) Raman Spectroscopy, recorded on the 30 th day growth of the microalgal species.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.3.
plain- Asserted: passes — The authors put it forward as true.
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It may state two separate claims as one.
- Rests on an assumption: Integrated band areas in FTIR and Raman spectra are proportional to the amount of the corresponding lipid component.
A result the paper reports from its own data — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“The percentage of SFA from the FTIR spectra was 93 for M.contortum, 83 for Chlamydomonas sp.74 for Pseudomuriella sp.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Spectroscopic investigations were performed to analyze the biomolecular transitions
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- Rests on an assumption: Integrated band areas in FTIR and Raman spectra are proportional to the amount of the corresponding lipid component.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“During the early exponential phase, when there is sufficient availability of nutrients, the microalgal cells divide, but as the cells enter the stationary phase, the nutrient availability becomes limited, the cell division stops, the algal cells start to accumulate and stores more energy in the form of lipids and carbohydrates.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.1. Second derivative analysis on each species at their various growth phases:
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In the paper
“The characteristic bands of hydrocarbons are the four bands at ~ 2960cm -1 ( as CH 3 ), 2920cm -1 ( as CH 2 ), 2870 cm -1 ( s CH 3 ) and 2850 cm -1 ( s CH 2 ) [22,26].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
What the sources say
- Not checked yetcites [22]
- Not checked yetcites [26] source
plain- Asserted: passes — The authors put it forward as true.
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In the paper
“Previous studies on green algal species like Chlamydomonas reinhardtii and Scenedesmus subspicatus have exhibited 5 to 6 fold increase in lipid accumulation [8]”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Relative content of lipids:
What the sources say
- Not checked yetcites [8] source
plain- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“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.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Abstract
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In the paper
“the FAME were identified using fatty acid standards (Sigma, Supleco, 37 FAMEs).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 2.6. Fatty acid quantification by Gas chromatography (GC)
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In the paper
“SFA and MUFA in microalgae can be an excellent source of biodiesel due to their high oxidative stability and lesser NO X emissions in comparison to polyunsaturated fatty acids (PUFA), except that the high melting point of SFA can cause gelling of fuel in cold weather.[12,13].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
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In the paper
“The analysis involves the measurement of absorption (FTIR)/scattering (Raman) intensity in relation to a range of molecular vibrational modes due to the presence of biomolecules, enabling quantification.[18,20,21].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
What the sources say
- Not checked yetcites [18]
- Not checked yetcites [20] source
- Not checked yetcites [21]
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In the paper
“However, the methods require extraction of lipids from algal biomass prior to analysis and are destructive, time consuming, also involves large amount of biomass, costly chemical reagents for analysis and therefore cannot be effectively used for screening large number of microalgal samples [14][15][16].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
What the sources say
- Not checked yetcites [14][15][16]
plaindirect- Asserted: passes — The authors put it forward as true.
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In the paper
“Microalgal species like Chlorella, Haemattococcus, Dunaliella , Spirulina , Nannochloropsis, Scenedesmus, Chlamydomonas and Monoraphidium have been reported as promising species for biodiesel applications through traditional lipid quantification methods [10,46,47].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
What the sources say
plaincorrelational- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“This confirms that, these microalgal species are accumulating more triacylglycerides (TAGs) than the other forms of lipids, which is a good indicator for biodiesel production.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
boostedcorrelational- Asserted: passes — The authors put it forward as true.
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What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“During incubation, the monospecificity of the cultures were verified periodically by microscopic observation and no evidence of contamination was found.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 2.1. Microalgal strains and culture conditions
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In the paper
“Spectra were recorded for three replicates per sample, resulting in 9 spectra at every phase of growth (10 th to 40 th day) for all three species yielding a total of 108 spectra.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 2.3. FTIR spectroscopy and measurements
plainn = 3- Asserted: passes — The authors put it forward as true.
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Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
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In the paper
“The exposure time was optimally chosen by ensuring that there was no laser induced damage for the algal biomass.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 2.4. Raman spectroscopy and measurements
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Probably not a substantial claim. The paper’s conclusions may not depend on it.
In the paper
“Spectroscopic techniques such as Fourier transformed infrared spectroscopy (FTIR) and Raman spectroscopy have been reported to be non-destructive, fast and versatile tools to analyze algal biomass using minimal volume with much ease [17][18][19].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
What the sources say
- Not checked yetcites [17][18][19]
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“A total of 36 spectra were recorded for the three species in triplicate at the four intervals of their growth phases.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 2.4. Raman spectroscopy and measurements
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
None of the sources cited for this claim have been checked yet.
In the paper
“TAGs are neutral lipids primarily made up of saturated (SFA) and monounsaturated fatty acids (MUFA) [10,11] and are the preferred compounds for biodiesel (Section 1).”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.2. Raman spectral analysis on the lipid accumulation in green microalgal species
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it. It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“However, it is affected by uneven dye uptake due to differences in cell wall composition among species.Nile red staining is not quantitative as chromatographic methods and cannot distinguish between neutral and polar lipids [5,8].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
None of the sources cited for this claim have been checked yet.
In the paper
“Among the three species, increased accumulation of TAGs (Fig. 5) was observed for M.contortum which indicate that the species is rich with saturated and monounsaturated fatty acids [10,11,47].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.1.2.
What the sources say
hedgedcorrelational- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
In the paper
“Among them green algal species, Chlorella sp. has exhibited 2 to 4 fold increase in lipid content, under nitrogen starved condition [48].”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 1. Introduction
What the sources say
- Not checked yetcites [48] source
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“In conclusion, FTIR and Raman spectroscopy enabled better understanding of biomolecular transitions and a rapid and easy assessment of lipid accumulation, especially to quantify fatty acids without the need for the extraction of lipids.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Spectroscopic investigations were performed to analyze the biomolecular transitions
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
- Rests on an assumption: Integrated band areas in FTIR and Raman spectra are proportional to the amount of the corresponding lipid component.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Each spectrum is an average of 3 replicates.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Spectroscopic investigations were performed to analyze the biomolecular transitions
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
A conclusion the paper draws from its own results — it cites no other source for it, so there is none to check. The quote shows it is in the paper.
In the paper
“Thus quantification of fatty acids by the FTIR and Raman spectroscopic methods was fast, reliable and non-destructive.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.3.
plaindirect- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: passes — The paper’s conclusions depend on it.
- Based: passes — The paper gives a reason why it holds.
It may state two separate claims as one.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Each point is the mean (±SE) of 9 replicates.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Spectroscopic investigations were performed to analyze the biomolecular transitions
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
What the paper did — it cites no source for this, so there is none to check. The quote shows it is in the paper.
In the paper
“Each spectrum is an average of 9 replicates.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > Spectroscopic investigations were performed to analyze the biomolecular transitions
plain- Asserted: passes — The authors put it forward as true.
- Checkable: passes — It can be checked against evidence.
- Load-bearing: fails — The paper’s conclusions may not depend on it.
- Based: passes — The paper gives a reason why it holds.
Probably not a substantial claim. The paper’s conclusions may not depend on it.
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.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
The source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“SD spectroscopy enables accurate measurements of wavelength position by identifying small and overlapping peaks that are not resolved in the original spectra. [23,46,47].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
Experimental — accuracy not yet measuredThe cited source says what the claim attributes to it.
In the citing paper
“Many of the studies have reported the use of FTIR spectroscopy in the rapid assessment of lipids, without the need for lipid extraction and to monitor the changes within the intracellular macromolecular pools of microalgae [15,20 -23].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
In the citing paper
“Two green microalgae species Monoraphidium contortum (M. contortum) and Chlamydomonas sp. that were identified to accumulate lipids were subjected to four different nutrient treatments (NP1-NP4)”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
In the citing paper
“The pattern of the spectra and the bands present in the two species conform to the spectra of the green microalgae [18,23,53,55].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
In the citing paper
“As SD spectra enhance the spectral resolution, the presence of all the four characteristic stretches of hydrocarbons ( ν asCH3 , ν asCH2 , ν sCH3 , ν sCH2) was revealed by the SD-FTIR (Fig. 1B) and SD-Raman spectra (Fig. 1D) in the expected region 3000 -2800 cm -1 [23,52,54].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
In the citing paper
“Similarly, for Chlamydomonas sp ., (Fig.3 and 4) their biomolecular groups were identified and the variation in the intensity of the peaks between NP treatments and the days of growth was assessed and is tabulated in Table 3 [9,20,23,52 -54].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
In the citing paper
“have shown a two to threefold increase in hydrocarbons and a six to sevenfold increase in TAGs during the declining phase (40 th day of growth) of the cells [23].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
In the citing paper
“The peak area (negative maximum) in sq. units itself will be directly proportional to the concentration, which can be taken as the absolute content [23,44,47].”
From Response to nutrient variation on lipid productivity in green microalgae captured using second derivative FTIR and Raman spectroscopy (2022) · cites this paper as [23]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Rated major: it would touch a result — a value a result rests on, reported and recomputed p-values on opposite sides of the significance level, two passages that conflict with no sign which is right, or a cited work retracted before this paper was published.
In the paper
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.3.
“The results of GC analysis for the three microalgal species on their 30 th day of growth (Fig. 10a) showed maximum SFA for Chlamydomonas sp.”
§ Biomolecular transitions and lipid accumulation in green microalgae monitored by FTIR and Raman analysis > 3.3.
“The spectral results on the fatty acids showed an increasing concentration of SFA in the microalgal species in the order, M. contortum > Chlamydomonas sp.> Pseudomuriella sp.”
Citations
Cites
A RAPID METHOD OF TOTAL LIPID EXTRACTION AND PURIFICATION
Bligh, E. G., & Dyer, W. J. (1959) · Canadian Journal of Biochemistry and Physiology · doi:10.1139/o59-099 · Cited by 54,751
Chisti, Y. (2007) · Biotechnology Advances · doi:10.1016/j.biotechadv.2007.02.001 · Cited by 9,524
Infrared Spectroscopy: Fundamentals and Applications
Stuart, B. H. (2004) · Analytical Techniques in the Sciences · doi:10.1002/0470011149 · Cited by 4,427
Rodolfi, L., Chini Zittelli, G., Bassi, N., Padovani, G., Biondi, N., Bonini, G., & Tredici, M. R. (2009) · Biotechnology and Bioengineering · doi:10.1002/bit.22033 · Cited by 2,879
Reference database of Raman spectra of biological molecules
De Gelder, J., De Gussem, K., Vandenabeele, P., & Moens, L. (2007) · Journal of Raman Spectroscopy · doi:10.1002/jrs.1734 · Cited by 1,425
Infrared and Raman Spectroscopy
Larkin, P. J. (2011) · Elsevier eBooks · doi:10.1016/c2010-0-68479-3 · Cited by 1,387
Williams, P. J. L. B., & Laurens, L. M. L. (2010) · Energy & Environmental Science · doi:10.1039/b924978h · Cited by 1,223
Raman spectroscopy of lipids: A review
Czamara, K., Majzner, K., Pacia, M. Z., Kochan, K., Kaczor, A., & Baranska, M. (2015) · Journal of Raman Spectroscopy · doi:10.1002/jrs.4607 · Cited by 1,089
Increase in Chlorella strains calorific values when grown in low nitrogen medium
Illman, A. M., Scragg, A. H., & Shales, S. W. (2000) · Enzyme and Microbial Technology · doi:10.1016/s0141-0229(00)00266-0 · Cited by 1,008
High lipid induction in microalgae for biodiesel production
Sharma, K. K., Schuhmann, H., & Schenk, P. M. (2012) · Energies · doi:10.3390/en5051532 · Cited by 886
Research works printed but not linked: 2
- Stehfest, 2005, vol. 43, 717
- Driver, 2015, vol. 11, 148
Cited by
Sorted by citations
Kassem, A., Abbas, L., Coutinho, O., Opara, S., Najaf, H., Kasperek, D., Pokhrel, K., Li, X., & Tiquia-Arashiro, S. M. (2023) · Frontiers in Microbiology · doi:10.3389/fmicb.2023.1304081 · Cited by 254
Kamnev, A. A., Dyatlova, Y. A., Kenzhegulov, O. A., Vladimirova, A. A., Mamchenkova, P. V., & Tugarova, A. V. (2021) · Molecules · doi:10.3390/molecules26041146 · Cited by 147
Atudorei, D., Stroe, S.-G., & Codină, G. G. (2021) · Plants · doi:10.3390/plants10030592 · Cited by 116
Batool, F., Mohyuddin, A., Amjad, A., Hassan, A. U., Nadeem, S., Javed, M., Othman, M. H. D., Chew, K. W., Rauf, A., & Kurniawan, T. A. (2023) · Chemical Engineering Science · doi:10.1016/j.ces.2023.119072 · Cited by 89
Valorization of Microalgae Biomass to Biofuel Production: A review
Razzak, S. A., Lucky, R. A., Hossain, M. M., & deLasa, H. (2022) · Energy Nexus · doi:10.1016/j.nexus.2022.100139 · Cited by 86
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
- Semantic Scholar
- 9cd4a545f5cae8512e3bba170cd971bc4805224a
- 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
- bronze
- doi.org
- 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
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
A language model drew the claims from the paper on 2026-10-07, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).
A second model labelled each claim on 2026-10-07 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).
Cited sources are checked with a language model’s help (gpt-6-sol).
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
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