Nutritional value changes in response to temperature, microalgae mono and mixed cultures

Aim: The performance of the mixed cultures and monocultures of Pseudopediastrum boryanum (Turpin) E. Hegewald and Scenedesmus obliquus (Turpin) Kutzing at three different temperatures, 20, 30 and 40 °C, in laboratory scale, in terms of biomass and biochemical composition is evaluetade. Methods: Microalgae were placed in a batch culture during 21 days, in ASM1 medium. Cell density was determined by direct couting in Fuchs-Rosenthal hemocytometer every 2 days. Chlorophyll ‘a’ and total carotenoids were extract two times. Protein, carbohydrates, total lipids and fatty acids contend were determined at the end of the experiment. Results: There was not growth for the cultures in 40 °C. Increased cell density (13.6 x 106 cell.mL-1) and biomass (55 g.L-1) were recorded in unialgal S. obliquus culture at 30 °C. High protein concentrations (672.6 mg.g-1) were observed in unialgal P. boryanum and S. obliquus at 20 °C treatments and carbohydrates (6.17 mg.g-1) in P. boryanum unialgal at 30 °C. There was no significant difference in total lipid content extracted in S. obliquus (95.5 mg.g-1), P. boryanum (96.3 mg.g-1) and the mixed culture at 20 °C (105.3 mg.g-1). FAMEs varied significantly regarding the number of unsaturations, were constituted predominantly by fatty acids with two or more unsaturations. Conclusion: The biomass of the treatments analyzed was rich in proteins, essential fatty acids, such as linolenic acid, and had low carbohydrate content, suggesting its potential use as a food supplement. Our results indicate that mixed culture of P. boryanum and S. obliquus were not efficient condition for biomass or biochemical compounds production than unialgal cultivations. However, algae grown in consortium showed better stability in their biochemical composition in response to changes in temperature, an important factor for microalgae production in open ponds and for ensuring the food safety. These results suggest the consortia among different species of microalgae should be tested to determine better methodologies for the production of biomass and metabolites with greater stability to environmental factors.