Abstract
The lipid composition in terms of the amount of neutral lipids, free fatty acids and polar lipid content is of great importance to make full use possible of this fraction and to define the suitability of its application, either as a raw material for fuel production, nutraceutical purposes or feed. In addition to the fatty components present in the lipid extract, other components may be included, such as: carotenoids, pigments and sterols. The microalgae studied in this work, Scenedesmus sp. and Desmodesmus sp., were subjected to the same growth conditions and evaluated for lipid content, quantification and diversity of lipid components as well as its fatty acid profile. For lipid determination two extraction methods were compared: the J: Schmid-Bondzynski-Ratzlaff and Bligh & Dyer method. For Desmodesmus sp. 5.43% ± 0.41% and 9.18% ± 0.33% of lipids were obtained on an ash-free dry weight basis and for Scenedesmus sp. 12.46% ± 0.38% and 8.16% ± 0.42% of lipids were obtained on an ash-free dry weight basis using for both methods J: Schmid-Bondzynski-Ratzlaff and Bligh & Dyer, respectively. For the identification of the main lipid components present in the extracts, the Thin layer chromatography (TLC) technique was used. This made it possible, using a simple and inexpensive method, to identify the compounds extracted by different extraction methods, that is, it was possible to verify the selectivity of the different extraction methods. In addition, it has been shown that using these methods, widely described in the literature as methods of extracting lipids in practice, extracts a wide diversity of compounds. The major lipid class for both microalgae was fatty acids with amounts between 23.62% - 38.02%. The triglycerides percentage in biomasses without chemical treatment did not exceed 18.26%. In the lipid extract obtained with Bligh & Dyer, the microalgae Desmodesmus sp. presented 55.26% of unsaponifiable material, higher than the amount present using the same extraction method for Scenedesmus sp. 49.06%. Among the main unsaponifiables identified are hydrocarbons (carotenes) and sterols esters. The acid treatment of biomass, method J: Schmid-Bondzynski-Ratzlaff, showed selectivity of 72.84% and 76.66% for obtaining fatty material from the microalgae Desmodesmus sp. and Scenedesmus sp., respectively. The results showed that depending on the method used for extraction, the lipid fraction will be different in relation to the percentage of fatty components.
Highlights
The term “biomass” means any organic matter that is available on a recurring or renewable basis including, plants, agricultural waste, aquatic plants, wood and wood waste, animal waste, municipal waste and other waste used for industrial energy production, fuels, chemicals and materials [1] [2] [3].An emerging alternative is the use of aquatic biomass, it is estimated that the global primary production of biomass is 50% aquatic and 50% terrestrial
For Desmodesmus sp. 5.43% ± 0.41% and 9.18% ± 0.33% of lipids were obtained on an ash-free dry weight basis and for Scenedesmus sp. 12.46% ± 0.38% and 8.16% ± 0.42% of lipids were obtained on ash-free dry weight basis using for both methods J: Schmid-BondzynskiRatzlaff and Bligh & Dyer, respectively
In the microalgae Desmodesmus sp. the recovery of lipids using the Bligh-Dyer method was 9.18% ± 0.33% slightly higher than that obtained for the microalgae Scenedesmus sp
Summary
An emerging alternative is the use of aquatic biomass, it is estimated that the global primary production of biomass is 50% aquatic and 50% terrestrial To this day, government policies have focused almost exclusively on the use of terrestrial biomass, paying little attention to aquatic crops, taking as examples macro and microalgae. The development of an effective technique in the process of extracting lipids on a large scale from microalgae biomass is still a challenge for researchers [10] [11]. It is believed that the extraction process represents an important limitation for the use of microalgae lipids as fuels. Microalgae have a resistant cell wall, which is a major barrier to the extraction processes and the procedure for breaking the cell wall is an important operation to obtain the compounds of interest. Some cell disruption techniques have been used to improve extraction efficiency, such as: the chemical treatment of biomass [14] [15]
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