Lipid quantification techniques for screening oleaginous species of microalgae for biofuel production

Abstract

This review examines the available literature on quantifying lipids in microalgae suitable for biofuels research. It discusses their advantages and disadvantages, their prevalence in the literature, and draws conclusions about the best way to approach choosing a suitable lipid measurement technique for microalgal biofuels research. We conclude that the method must be chosen based on the following key criteria: (1) the level of detail required in the results, and (2) the amount of biomass that can be spared for the assay. This review establishes that no method can be used as a "golden standard" for all microalgae. However, we present a systematic decision chart to choose the best measurement method or combination of methods to provide a guide to those wishing to understand the differences between the myriad of lipid measurement techniques.Practical applications: This review will allow researchers new to the field to choose the most appropriate techniques for quantifying lipids in the microalgal species under study. The review is also intended to act as a gateway to the wider literature and will enable researchers to look in depth at a particular technique before carrying out experimental work.

Lipids detection and quantification in oleaginous microorganisms: an overview of the current state of the art

“…Corncob waste liquor 22 [18] Bacteria Rhodococcus opacus DSM 1069 Ethanol organosolv lignin 4 [19] R. opacus PD630 Dairy wastewater 14 [20] amounts [31,32]. To this end, several alternative techniques enabling high-throughput and reliable lipid quantification have emerged recently [31,33]. Fluorescence spectroscopy is considered the simplest and most cost-effective alternative to gravimetric methods for lipid quantification, and fluorescence detection methods have been developed for direct lipid measurements [34][35][36].…”

“…Other non-destructive methods, such as infrared (IR), nuclear magnetic resonance (NMR), and Raman spectroscopy, have also been used to some extent for lipid determination in oleaginous microorganisms [38][39][40][41][42]. Techniques for lipid content determination in microalgae have been thoroughly described in several recent reviews [31,[33][34][35] and are also commonly applied to lipid quantification in other oleaginous microorganisms. Other important factors, such as the degree of unsaturation and saturation, the position and number of double bonds in the hydrocarbon chain, the amount of free fatty acids, TAGs, diacylglycerols (DAGs), monoacylglycerols (MAGs), and steryl esters, should also be taken into consideration when evaluating microbial lipids for biofuels [43].…”

“…Various conventional chromatographic/spectrometric methods for lipid quantification and profiling of oleaginous microorganisms are presented in Table 4. The most commonly applied steps before LC or GC are cell lysis and lipid extraction, as well as the conversion of saponifiable lipids directly into acyl esters of fatty acids via a transesterification reaction [33]. The reaction includes the addition of an acid or base as catalyst and an alcohol, most often methanol [99].…”

“…Other methods such as TD-NMR and SPV are species-specific and their accuracy varies among species. Accordingly, their protocol requires some modifications before unknown samples can be accurately analyzed [33]. Raman spectrometric methods can be applied to single cells, but they do not show good accuracy with samples containing fluorescent pigments and carotenoids [145].…”

Biofuel metabolic engineering with biosensors

“…Most metabolites, except for special cases or by the use of exogenous chemical dyes (reviewed in [4]), cannot be measured using rapid optical methods. Chromatography and mass spectrometry (MS) are thus the only analytical tools available for measuring most biofuel-related metabolites despite their low throughput.…”