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Resumo: Este estudo avaliou a influência de seis meios de cultura alternativos (um a base de NPK, dois contendo extrato de Pistia stratiotes e Eichhornia crassipes enriquecido de NPK, e outros três com diferentes diluições de extrato puro de E. crassipes, (Eic 40, Eic 85, Eic 130) em comparação ao meio de cultura comercial ASM-1, no desenvolvimento da microalga Scenedesmus acuminatus. Foram avaliados taxa de crescimento (K), densidade, volume celular, biovolume e qualidade nutricional dos meios de cultura. Os meios de culturas testados apresentaram concentração de nutrientes suficiente para o crescimento da microalga. As taxas de crescimento de ASM-1 (0,439) foram similares (p>0,05) a NPK, Pis + NPK e Eic + NPK. Eic 85 e Eic 130 apresentaram os valores mais baixos (0,201; 0,150, respectivamente) e similares entre si. Os volumes dos tratamentos não diferiram de ASM-1 (135,427 μm3), somente o Eic NPK e Eic 130 apresentaram valores menores (86,780 e 100,401 μm3, respectivamente). O maior biovolume e densidade celular foram encontrados em Eic NPK (1,273 mm3.L-1 e 1047 x 104 cél.mL-1). Os tratamentos apresentaram capacidade de nutrição muito similar ao ASM-1, podendo substitui-lo no cultivo de S. acuminatus, em especial Eic + NPK que apresentou maior densidade e biovolume. Os tratamentos com extrato puro, apesar de apresentarem resultados mais baixos, ainda assim possibilitaram o desenvolvimento da alga. Palavras-chave:Cultivo. Microalga. Macrófitas. NPK. Meio de cultura.Abstract: This study evaluated the influence of six alternative culture media (one of NPK, two containing Pistia stratiotes and Eichhornia crassipes extracts enriched with NPK, and three with different dilutions of pure extract of E. crassipes (Eic 40, Eic 85, Eic 130) compared to the commercial culture medium ASM-1 in the development of the microalga Scenedesmus acuminatus. Growth rate (K), density, cell volume, biovolume and nutritional quality of culture media were evaluated. The tested media had enough concentration of nutrients for the growth of microalgae. The growth rate of ASM-1 (0.439) were similar (p> 0.05) to NPK, NPK + Pis and Eic + NPK. Eic 85 and Eic 130 had the lowest values (0.201; 0.150, respectively) and similar to each other. The volumes of the treatments did not differ to ASM-1 (135.427 μm3), only Eic + NPK and Eic 130 had lower values (86.780 and 100.401 μm3, respectively). The highest biovolume and cell density were found in Eic + NPK (1.273 mm3.L-1 and 1047 x 104 cél.mL-1). It was concluded that the treatments had very similar nutritional ability to ASM-1 and may replace it in the cultivation of S. acuminatus. In particular Eic + NPK with the highest density and biovolume. The treatments with pure extract, despite having lower results, still allowed the development of algae.

Aim The response of mixed cultures and monocultures of Pseudopediastrum boryanum (Turpin) E. Hegewald and Scenedesmus obliquus (Turpin) Kützing was assessed in the laboratory at three different temperatures: 20, 30 and 40 °C. The change in biomass and biochemical composition of these cultures was evaluated. Methods Microalgae were placed in a batch culture over 21-days in ASM1 medium. Cell density was directly counted every two days using a Fuchs-Rosenthal hemocytometer. Chlorophyll ‘a’ and total carotenoids were extracted twice. Protein, carbohydrate, total lipid and fatty acid contents were determined at the end of the experiment. Results Cultures grown in 40 °C exhibited no growth. However, there was increased cell density (13.6 x 106 cell.mL-1) and biomass (55 g.L-1) in the S. obliquus monoculture at 30 °C. High protein concentrations (672.6 mg.g-1) were observed in monocultures P. boryanum and S. obliquus at 20 °C treatments. There were high carbohydrate concentrations (6.17 mg.g-1) in P. boryanum unialgal at 30 °C. There was no significant difference in total lipid content between 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 unsaturated components, which predominantly consisted of fatty acids with two or more unsaturated bonds. Conclusions The biomass of the treatments analyzed was rich in proteins and essential fatty acids (such as linolenic acid), yet low in carbohydrate content, suggesting its potential use as a food supplement. Our results indicate that mixed culture of P. boryanum and S. obliquus was inefficient in cultivating biomass or biochemical compounds as compared to the unialgal cultivations. However, algae grown together showed better stability in their biochemical composition in response to changes in temperature, an important factor for microalgae production in open ponds and in food safety measures. 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 towards environmental factors.

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