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The growing global demand for food has led the search for new sources of highly nutritious biomass. Cyanobacteria can be used not only as a source of compounds of biotechnological interest, but also as food for animals and humans, because of their high nutritional quality. The aim of this work was to evaluate the nutritional quality of biomass from four strains of nitrogenfixing filamentous cyanobacteria in batch cultures. Nostoc LAUN015, Nostoc UAM206, Anabaena MOF015 and Anabaena MOF016 were cultured in diazotrophic conditions at laboratory scale. The biomass was harvested, dried and used for biochemical evaluation, proximal, microbiological and toxicological quality. Biomass protein has values between 25 and 40%, 43-48% of carbohydrates, 0.39 to 1.64% of fiber and 0.74-1.05% of lipids. Biomass is rich in amino acids, specially arginine, lysine, aspartate and glutamate. Pathogens such as S. aureus, total and fecal coliforms, E. coli and Salmonella, were undetected. Toxicology tests showed high LC50 for Anabaena MOF015, indicating no toxicity. In conclusion, Anabaena MOF015 stands within the group, for having an excellent biomass production, nutritional quality and no toxicity detected, and could be used as a protein source for human and animal nutrition. [ABSTRACT FROM AUTHOR]

Changes in salinity, temperature and irradiance during wet and dry seasons have induced metabolic versatility in cyanobacteria from saline environments. Cyanobacteria from these environments have biotechnological potential for the production of metabolites with pharmaceutical and industrial interest. We studied the growth, dry mass and metabolite production of the cyanobacterium Synechococcus sp. MOF-03 in function of irradiance (78, 156 and 234 micromol q m(-2) s(-1)). All batch cultures were maintained by triplicate in constant aeration, 12:12 h photoperiod, 30 +/- 2 degrees C and 35% per hundred. Maximum values of protein, carbohydrates and lipids, of 530.19 +/- 11.16, 408.94 +/- 4.27 and 56.20 +/- 1.17 microg ml(-1), respectively, were achieved at 78 micromol q m(-2) s(-1). Pigments, analyzed by HPLC, showed maximum values at 78 micromol q m(-2) s(-1) for chlorophyll a with 7.72 +/- 0.16 microg ml(-1), and at 234 micromol q m(-2) s(-1) for beta-carotene and zeaxanthin with 0.70 +/- 0.01 and 0.67 +/- 0.05 microg ml(-1). Chlorophyll a:beta-carotene ratio decreased from 17.15 to 6.91 at 78 and 234 micromol q m(-2) s(-'1); whereas beta-carotene:zeaxanthin ratio showed no changes between 78 and 156 micromol q m(-2) s(-1), around 1.21, and decreased at 234 micromol q m(-2) s(-1), to 1.04. Also, this cyanobacterium produced the greatest cell density and dry mass at 156 micromol q m(-2) s(-1), with 406.13 +/- 21.74 x l0(6) cell ml(-1) and 1.49 +/- 0.11 mg ml(-1), respectively. Exopolysaccharide production was stable between 156 y 234 micromol q m(-2) s(-1), around 110 microg ml(-1). This Synechococcus strain shows a great potential for the production of enriched biomass with high commercial value metabolites.