No abstract

Thraustochytrids are unicellular protists belonging to the Labyrinthulomycetes class, which are characterized by the presence of a high lipid content that could replace conventional fatty acids. They show a wide geographic distribution, however their diversity in the Antarctic Region is rather scarce. The analysis based on the complete sequence of 18S rRNA gene showed that strain 34-2 belongs to the species Thraustochytrium kinnei, with 99% identity. The total lipid profile shows a wide range of saturated fatty acids with abundance of palmitic acid (16:0), showing a range of 16.1–19.7%. On the other hand, long-chain polyunsaturated fatty acids, mainly docosahexaenoic acid and eicosapentaenoic acid are present in a range of 24–48% and 6.1–9.3%, respectively. All factors analyzed in cells (biomass, carbon consumption and lipid content) changed with variations of culture temperature (10 °C and 25 °C). The growth in glucose at a temperature of 10 °C presented the most favorable conditions to produce omega-3fatty acid. This research provides the identification and characterization of a Thraustochytrids strain, with a total lipid content that presents potential applications in the production of nutritional supplements and as well biofuels.

Thraustochytrids are marine protists found throughout the world in estuarine and marine habitats. These microorganisms have attracted interest, because their lipids contain different long chain polyunsaturated fatty acids (PUFAs). Those able to produce docosahexaenoic acid (C22:6 n-3, DHA) are the most studied because of the physiological importance of this PUFA in human beings. Their heterotrophic cultivation offers several challenges since biomass, lipid content, and fatty acid profile are dependent on growth conditions. In this work the effects of C source and its concentration on DHA production by different thraustochytrid strains are reviewed. Results obtained by different investigators on the use of alternative and low cost nutrient sources for production of DHA by thraustochytrids are also presented.

Liquid residues from beer (RB) and potato (RP) processing were evaluated as carbon sources for the production of docosahexaenoic acid (C22:6n-3, DHA) by two native Thraustochytriidae sp., M12-X1 and C41, in shaking flask experiments. Results were compared with those obtained in the fermentations of glucose, maltose, soluble starch and ethanol. Both strains produced the highest biomass concentration (2.3 g/L) in the fermentation of RB supplemented with nitrogen sources [yeast extract (YE) and monosodium glutamate (MSG)]. DHA content in the fatty acids produced by the native thraustochytrids was dependent on the fermented carbon source; the fatty acids from biomass grown on carbon sources that permitted a lower growth rate contained more DHA. The highest DHA productivity [55.1 mg/(day L)] was obtained in the fermentation of RB-YE-MSG by M12-X1 strain. In this medium, M12-X1 strain grew at a specific growth rate of 0.014 h -1 and total fatty acid content in the biomass was 41.3%. Production of DHA by M12-X1 strain followed a non-growth rate associated pattern and DHA content in the biomass decreased significantly after growth ceased.

RESUMEN Alternativas biotecnológicas para la producción de ácidos grasos poliinsaturados omega-3Actualmente, los aceites de pescado son la principal fuente de ácidos grasos poliinsaturados (AGPI) del tipo omega-3 (ω3) como el ácido eicosapentaenoico (C20:5ω3) y el ácido docosahexaenoico (C22:6ω3). Se estima que en los próximos años la demanda por AGPI ω3 aumentará debido al crecimiento de la industria acuícola y al incremento en la demanda de AGPI específicos para la elaboración de suplementos alimenticios para humanos y animales. Fuentes alternativas para la producción de AGPI ω3 son bacterias, hongos, microalgas y thraustochytridos. La productividad de estos sistemas depende de las cepas y condiciones de fermentación. En general, las bacterias presentan bajas concentraciones de AGPI; las microalgas producen mezclas de AGPI; la productividad de los cultivos de hongos es baja debido a los largos tiempos de fermentación. A diferencia de és-tos, los cultivos heterotróficos de thraustochytridos presentan altas concentraciones de AGPI ω3 y varias cepas son capaces de producir un único AGPI ω3. Para que estas fuentes se transformen en alternativas reales de producción de AGPI ω3 es necesario optimizar los procesos de fermentación y desarrollar las tecnologías para la producción a gran escala. PALABRAS-CLAVE: Aceites marinos -DHA -Protistas marinos -Suplemento alimenticio -Thraustochytridos. SUMMARY Biotechnological alternatives for omega-3 polyunsaturated fatty acids productionFish oils are the main sources of omega-3 (ω3) polyunsaturated acids (PUFA) such as eicosapentaenoic (C20:5ω3) and docosahexaenoic (C22:6ω3) acids. World demand for ω3 PUFA shows an increasing trend mainly due to the growth of the aquaculture industry and also due to the increasing demand for specific PUFA used as food supplements. Bacteria, fungi, microalgae and thraustochytrids are biotechnological PUFA alternatives to fish oils. These sources are characterized by specific PUFA profiles whose productivity depends on strain and growth conditions. PUFA content in bacteria is low; microalgae synthesize mixtures of PUFA; fungi system productivity is low due to long Alternativas biotecnológicas para la producción de ácidos grasos poliinsaturados omega-3