Jose A. Gerde

Evaluation of microalgae cell disruption by ultrasonic treatment.

Microalgae are a promising feedstock for biofuels because of their capability to produce lipids. Cell disruption is necessary to maximize lipid extraction. Sonication conditions were evaluated for breaking heterotrophic (Schizochytrium limacinum) and autotrophic (Chlamydomonas reinhardtii) microalgae cells. Cell disruption was estimated by Nile red-lipids fluorescence quantification in S. limacinum and by the release of intracellular chlorophyll and carotenoids in green microalga C. reinhardtii. In both species, approximately 800 J/10 mL was the energy input necessary to maximize cell disruption, regardless of the cell concentrations studied. Increasing sonication time produced increasing amount of free radicals, quantified by the formation of hydroxyterephthalate. Sonication energy beyond the level needed for cell disruption induced oxidation of arachidonic acid, a polyunsaturated fatty acid typically found in marine lipids. Careful control of sonication conditions is necessary to maximize oil extraction at the lowest operational cost and to prevent oil from free radical-induced degradation.

Microalgae lipid characterization.

To meet the growing interest of utilizing microalgae biomass in the production of biofuels and nutraceutical and pharmaceutical lipids, we need suitable analytical methods and a comprehensive database for their lipid components. The objective of the present work was to demonstrate methodology and provide data on fatty acid composition, lipid class content and composition, characteristics of the unsaponifiables, and type of chlorophylls of five microalgae. Microalgae lipids were fractionated into TAG, FFA, and polar lipids using TLC, and the composition of fatty acids in total lipids and in each lipid class, hydrocarbons, and sterols were determined by GC-MS. Glyco- and phospholipids were profiled by LC/ESI-MS. Chlorophylls and their related metabolites were qualified by LC/APCI-MS. The melting and crystallization profiles of microalgae total lipids and their esters were analyzed by DSC to evaluate their potential biofuel applications. Significant differences and complexities of lipid composition among the algae tested were observed. The compositional information is valuable for strain selection, downstream biomass fractionation, and utilization.