Abstract
Microalgae produce a wide range of lipid compounds of potential commercial interest. Total lipid extraction performed by conventional extraction methods, relying on the chloroform-methanol solvent system are too laborious and time consuming for screening large numbers of samples. In this study, three previous extraction methods devised by Folch et al. (1957), Bligh and Dyer (1959) and Selstam and Öquist (1985) were compared and a faster single-step procedure was developed for extraction of total lipids from green microalgae. In the single-step procedure, 8 ml of a 2∶1 chloroform-methanol (v/v) mixture was added to fresh or frozen microalgal paste or pulverized dry algal biomass contained in a glass centrifuge tube. The biomass was manually suspended by vigorously shaking the tube for a few seconds and 2 ml of a 0.73% NaCl water solution was added. Phase separation was facilitated by 2 min of centrifugation at 350 g and the lower phase was recovered for analysis. An uncharacterized microalgal polyculture and the green microalgae Scenedesmus dimorphus, Selenastrum minutum, and Chlorella protothecoides were subjected to the different extraction methods and various techniques of biomass homogenization. The less labour intensive single-step procedure presented here allowed simultaneous recovery of total lipid extracts from multiple samples of green microalgae with quantitative yields and fatty acid profiles comparable to those of the previous methods. While the single-step procedure is highly correlated in lipid extractability (r2 = 0.985) to the previous method of Folch et al. (1957), it allowed at least five times higher sample throughput.
Highlights
Oleaginous microalgae have received considerable attention as a renewable source of oil for production of biodiesel and other fuels [1]
While specific analytical methods may exist for selected lipid compounds, total lipid extraction is favourable when screening for a variety of lipids
The increased solvent-to-sample ratios assumed here would reduce the importance of this factor as the capacity of the solvent system for retaining the monophasic system increases with its volume [14]
Summary
Oleaginous microalgae have received considerable attention as a renewable source of oil for production of biodiesel and other fuels [1]. Microalgae are known to synthesize a diversity of unusual lipid compounds which may be commercially exploitable [6,7,8] and have been proposed as a suitable biorefinery feedstock for value added co-production of fine chemicals and fuels [9]. The extraction methods devised by Folch et al [10] and by Bligh and Dyer [11] have found general acceptance as standard procedures for recovery of total lipids [12,13]. Both methods rely on chloroform and methanol to form a monophasic solvent system to extract and dissolve the lipids. A biphasic system is produced in a purification step by the addition of water, leading to the separation of polar and non-polar compounds into an upper and lower phase respectively [10,11]
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