Effect of temperature and nitrogen concentration on biomass composition of Heterochlorella luteoviridis

Abstract The interest in microalga as a food supplement has grown due their high contents of carotenoids, polyunsaturated fatty acids and proteins. This study evaluated the effect of different temperatures (22, 27 or 32 °C) and sodium nitrate concentrations (12, 24, 36, 48 or 60 mg L-1 of N-NO3) in culture medium on Heterochlorella luteoviridis biomass production and composition. The highest biomass concentration (3.35 g L-1) was observed at the highest N-NO3 concentration. The N-NO3 concentration positively affected protein, carbohydrate and carotenoids contents of biomass. On the other hand, cells cultured at the lowest N-NO3 concentration showed a slight increment in lipid content. The major carotenoid was lutein (30.7 ± 1.4% of total carotenoids), and the polyunsaturated fatty acids were 37 ± 2% of total fatty acids. Low temperature improved the biosynthesis of ω3 type fatty acids by lowering the ω6:ω3 ratio. Overall, our results indicate H. luteoviridis can yield high biomass concentration under autotrophic growth, resulting in a biomass rich in carotenoids, mainly lutein, and ω3 polyunsaturated fatty acids.

Avaliação sensorial de pães de fermentação natural a partir de culturas starters inovadoras / Sensory evaluation of natural fermentation breads with innovative starter cultures

A fermentação sourdough para a produção de pães é fortemente motivada por seus efeitos benéficos quanto ao sabor, textura, vida de prateleira e pelas propriedades nutricionais dos produtos obtidos. Nesta pesquisa, estudou-se a aplicação dos micro-organismos Kluyveromyces marxianus, Dekkera bruxellensis e Lactobacillus plantarum como culturas starters alternativas na produção de pães. A partir de sete ensaios resultantes de um delineamento de mistura simplex-centroide, foram realizadas nos pães análises sensorial e instrumental. Observou-se que pães produzidos com L. plantarum apresentaram menor volume específico, enquanto que a mistura entre K. marxianus e L. plantarum exerceu influência positiva, possibilitando obter produtos de maior volume específico. A análise sensorial demonstrou a boa aceitabilidade para os pães produzidos com a mistura entre D. bruxellensis e K. marxianus e para a mistura entre os três micro-organismos. Os resultados deste trabalho demonstram a possibilidade do uso de culturas starters definidas para a fermentação sourdough, que é tradicionalmente obtida sem controle de processo.

The sourdough fermentation in bread making is strongly motivated due to its beneficial aspects on flavor, texture, shelf life, and the nutritional properties of the obtained products. In this research, the yeasts Kluyveromyces marxianus and Dekkera bruxellensis, and the bacterium Lactobacillus plantarum were used as alternative starter cultures in bread making. Experimental designs generated from simplex-centroid mixture were used in the sensorial analyses of breads. Results have shown that bread obtained with pure cultures of L. plantarum presented the smallest specific volume, while the mixture of K. marxianus and L. plantarum positively influenced the formation of good specific volume of products. Sensorial analysis showed good acceptability for breads obtained with D. bruxellensis and K. marxianus mixture, as well as for the mixture of the three microorganisms. The results obtained in this research suggest the possibility of using defined starter cultures for sourdough fermentation, which is traditionally carried out without any process controls.