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Accurate and Reliable Quantification of Total Microalgal Fuel Potential as Fatty Acid Methyl Esters by in situ Transesterfication

Journal Article · · Analytical and Bioanalytical Chemistry
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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.
Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
DOE Contract Number:
AC36-08GO28308
OSTI ID:
1038343
Report Number(s):
NREL/JA-5100-53442
Journal Information:
Analytical and Bioanalytical Chemistry, Journal Name: Analytical and Bioanalytical Chemistry Journal Issue: 1 Vol. 403; ISSN 1618-2642
Country of Publication:
United States
Language:
English

References (15)

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Related Subjects

09 BIOMASS FUELS
59 BASIC BIOLOGICAL SCIENCES
ACCURACY
ALGAE
BIOFUELS
BIOMASS
CARBOXYLIC ACIDS
CATALYSTS
CHLORELLA
ESTERS
GC
LIPIDS
MASS BALANCE
MONITORING
WATER
algae
bioanalytical methods
catalysts
fatty acids
fuels