Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) for Rapid Determination of Microbial Cell Lipid Content: Correlation with Gas Chromatography-Mass Spectrometry (GC-MS)

Abstract

There is a growing interest worldwide for the production of renewable oil without mobilizing agriculture lands; fast and reliable methods are needed to identify highly oleaginous microorganisms of potential industrial interest. The aim of this study was to demonstrate the relevance of attenuated total reflection (ATR) spectroscopy to achieve this goal. To do so, the total lipid content of lyophilized samples of five Streptomyces strains with varying lipid content was assessed with two classical quantitative but time-consuming methods, gas chromatography-mass spectrometry (GC-MS) and ATR Fourier transform infrared (ATR FT-IR) spectroscopy in transmission mode with KBr pellets and the fast ATR method, often questioned for its lack of reliability. A linear correlation between these three methods was demonstrated allowing the establishment of equations to convert ATR values expressed as CO/amide I ratio, into micrograms of lipid per milligram of biomass. The ATR method proved to be as reliable and quantitative as the classical GC-MS and FT-IR in transmission mode methods but faster and more reproducible than the latter since it involves far less manipulation for sample preparation than the two others. Attenuated total reflection could be regarded as an efficient fast screening method to identify natural or genetically modified oleaginous microorganisms by the scientific community working in the field of bio-lipids.

Selective delivery of laser energy to ester bonds of triacylglycerol in lipid droplets of adipocyte using a quantum cascade laser

“…1(c). The adipocyte sample exhibited a specific absorbance at 1,738 cm −1 (indicated by the arrow), attributed to the absorbance by the ester bonds (C = O stretching) [12,13]. Consistently, the standard TAG sample of glyceryl trioleate also exhibited an intense absorption at 1,738 cm −1 , as shown in Fig.…”

“…Abundance and specificity in the absorption are required to investigate the selective delivery of MIR laser energy. Lipids satisfy both requirements, as the ester bonds exhibit a specific absorption in the range of 1,700-1,750 cm −1 [12,13], and the lipids are the second most abundant molecular species in an animal body, e.g., 15-40% in the mouse body [14]. In fact, influence of MIR radiation on fat cells has been investigated [15,16].…”

Negative Correlation between Lipid Content and Antibiotic Activity in Streptomyces: General Rule and Exceptions

“…Fifty-four randomly picked Streptomyces strains from our collection were grown for 72 h at 28 • C on the surface of cellophane disks deposited on the surface of the modified (no sucrose added) R2YE medium [6] limited in phosphate and containing either glucose (50 mM) or glycerol (100 mM) as the main carbon source. The lipid content of the strains was determined using the fast and reliable FTIRS method [22][23][24]. The FTIRS values, expressed as arbitrary units, were converted into µg of Fatty Methyl Esters (FAME) per mg of dry mycelium using the converting equation established by Millan-Oropeza et al (2017) [24].…”

“…In order to determine whether these observations constituted a general rule for Streptomyces species, fifty-four randomly picked Streptomyces strains from our collection were grown on modified solid R2YE medium limited in phosphate with either glucose or glycerol as the main carbon source. Their total lipid content, on glucose or glycerol, was assessed by Fourier transformed infra-red spectroscopy (FTIRS) [22][23][24], and the measure of the diameter of the growth inhibition zones around four agar plugs of each strain gave an estimation of their antibiotic activity against Micrococcus luteus (Figure 1). This study confirmed the existence of a negative correlation between lipid content and antibiotic activity but with some exceptions commented on in the discussion.…”

Wheat flag leaf epicuticular wax morphology and composition in response to moderate drought stress are revealed by SEM, FTIR‐ATR and synchrotron X‐ray spectroscopy

“…Recent observations by Jiang et al reported differences in pea pollen coat lipid composition between contrasting heat‐tolerant cultivars associated with improved yield using FTIR attenuated total internal reflectance (ATR) spectroscopy (Lahlali et al , Jiang et al ). Furthermore, analysis of plant tissue with ATR‐FTIR spectroscopy is non‐destructive (Lahlali et al , Jiang et al , Vijayan et al ) and requires less time for sample preparation and data collection than gas chromatography‐mass spectroscopy (Millan‐Oropeza et al ).…”