Accurate and reliable quantification of total microalgal fuel potential as fatty acid methyl esters by in situ transesterification

Abstract

In the context of algal biofuels, lipids, or better aliphatic chains of the fatty acids, are perhaps the most important constituents of algal biomass. Accurate quantification of lipids and their respective fuel yield is crucial for comparison of algal strains and growth conditions and for process monitoring. As an alternative to traditional solvent-based lipid extraction procedures, we have developed a robust whole-biomass in situ transesterification procedure for quantification of algal lipids (as fatty acid methyl esters, FAMEs) that (a) can be carried out on a small scale (using 4–7 mg of biomass), (b) is applicable to a range of different species, (c) consists of a single-step reaction, (d) is robust over a range of different temperature and time combinations, and (e) tolerant to at least 50% water in the biomass. Unlike gravimetric lipid quantification, which can over- or underestimate the lipid content, whole biomass transesterification reflects the true potential fuel yield of algal biomass. We report here on the comparison of the yield of FAMEs by using different catalysts and catalyst combinations, with the acid catalyst HCl providing a consistently high level of conversion of fatty acids with a precision of 1.9% relative standard deviation. We investigate the influence of reaction time, temperature, and biomass water content on the measured FAME content and profile for 4 different samples of algae (replete and deplete Chlorella vulgaris, replete Phaeodactylum tricornutum, and replete Nannochloropsis sp.). We conclude by demonstrating a full mass balance closure of all fatty acids around a traditional lipid extraction process.FigureAccurate quantification of different types of lipids in algal biomass using a comprehensive study of reaction parameters.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-012-5814-0) contains supplementary material, which is available to authorized users.

Biochemical characterization of microalgal biomass from freshwater species isolated in Alberta, Canada for animal feed applications

“…This issue is further complicated for algal biomass where standard extraction procedures are not well established [49,51]. In particular, organic/aqueous solvent extraction of algal biomass using a Soxhlet reactor almost always leaves residual oil in the biomass to varying degrees, especially in the absence of a chemical and/or enzymatic cell-lysis step [37] and this was clearly evident in the present study. The species studied here were mechanically pulverized (Retsch mill) and then 'de-fatted' by solvent extraction under identical conditions (CHCl 3 :CH 3 OH [2:1 v/v], 150°C, 82 min) [22] and the difference in their lipid-releasing characteristics was profound.…”

“…Vast diversity in species/strains, isolate geographical environment, culture conditions, harvesting/processing techniques and poorly defined biomass characterization methods have resulted in data that is difficult to reproduce and confidently apply to industrial applications [1,23,[35][36][37]. The present study generated new data on the biochemical composition of four novel freshwater microalgae isolates identified as promising candidates for industrial CO 2 conversion in Northern climates.…”

Effects of pulsed electric field treatment on enhancing lipid recovery from the microalga, Scenedesmus

“…FAME recovery was always lower than crude lipid recovery for all solvents, indicating co-extraction of non-lipid components, like protein, carbohydrate, and pigment (Laurens et al, 2012). Several combinations of isopropanol and Folch solvents following FP treatment yielded the maximum FAME-to-biomass ratio, around 21% (Fig 1b).…”

Optimization of One-Step In Situ Transesterification Method for Accurate Quantification of EPA in Nannochloropsis gaditana

“…However, base catalysis has high selectivity based on the type of lipids. Base catalysis methods showed lower FAME yield compared to the yield obtained by acid catalysis [19]. The base catalysts may not be able to penetrate through the thick algal cell wall and the existing free fatty acid may be subjected to saponification in base catalyzed transesterification.…”

“…After the reaction, the resulting FAME fraction was extracted by hexane and quantified by gas chromatography (GC) after neutralization. The procedure was duplicated under different reaction conditions with Methanol/biomass (mL/g) from 30 to 120; HCl/MeOH from 2.5 to 11; reaction temperature from 60 to 90 • C; and reaction time from 0.5-2.5 h. The procedure adopted here has been previously described in literature [19].…”