Isolation of a freshwater microalgae and its application for the treatment of wastewater and obtaining fatty acids from tilapia cultivation.

In the present study, isolated strains of the microalgae Chlamydomonas sp. (CH) and Chlorella vulgaris (CV) were used to treat aquaculture wastewater and to obtain fatty acids and from a fattening culture of tilapia. The microalgae were cultivated for 11 days in tubular photobioreactors with an operating volume of 2 L, constant aeration and illumination. High removal rates of NO3- and PO43- were achieved for both Chlamydomonas sp. (84.7% and 96%, respectively) and Chlorella vulgaris (94.6 and 97.9%, respectively). The maximum biomass productivity achieved by Chlamydomonas sp. was 0.06 and 0.10 gL-1d-1 for Chlorella vulgaris. Therefore, tilapia wastewater contained the necessary nutrient concentration for algal growth and development. Chlamydomonas sp. biomass lipid content was 69%, while that of Chlorella vulgaris was 40%. The lipid profile of both microalgae was abundant in palmitic acid (78% for Chlamydomonas sp. and 35% for Chlorella vulgaris). This fatty acid is suitable for biodiesel production. Tilapia wastewater is low-cost alternative culture medium as it contains the necessary nutrient concentration for microalgae development and growth.

Evaluation of colour temperatures in the cultivation of Dunaliella salina and Nannochloropsis oculata in the production of lipids and carbohydrates.

The production of biofuels from microalgae is a promising and sustainable alternative. Its production is determined by the content of lipids and carbohydrates, which is different for each microalgae species and is affected by environmental factors, being lighting one of the principal determining their biochemical composition. The colour temperature (electromagnetic radiation and light spectrum) is a determining factor for the production of lipids and carbohydrates in microalgae. The aim of this assay was to evaluate the effect of three colour temperatures (6500, 10,000 and 20,000 °K) on the biomass (cel mL-1), biomass production and productivity (g L-1 and g L-1 day-1), lipid and carbohydrate content (%), lipid and carbohydrate production and productivity (mg L-1 and mg L-1 day-1), composition and content of fatty acids (%) in two microalgae species: Dunaliella salina and Nannochloropsis oculata. The highest cell density was observed for N. oculata in stationary phase in the control (83.93 × 106 cel mL-1). However, higher lipid content was obtained in D. salina in stationary phase at 10,000 °K (80%), while N. oculata showed 67% at 6500 °K. The highest carbohydrate content was 25% in stationary phase for D. salina at 20,000 °K. Regarding the production of lipids, D. salina reached a maximum of 523 mg L-1 in exponential phase at 6500 and 10,000 °K. The highest carbohydrate production was 38 mg L-1 for D. salina in exponential phase at 20,000 °K. In both microalgae, 15 different fatty acids were identified; the most abundant was palmitic acid with 35.8% for N. oculata in stationary phase at 10,000 °K, while D. salina showed 67% of polyunsaturated fatty acids in exponential phase at 6500 °K. In conclusion, the ideal colour temperature for microalgae culture to obtain biofuels should be based on the biomolecule of interest, being necessary to individually evaluate for each species.

Effect of the pesticide lindane on the biomass of the microalgae Nannochloris oculata.

This study assesses the growth of the microalgae Nannochloris oculata in the presence of lindane and the ability of N. oculata to remove lindane from media. Algal biomass increased with 0.1 and 0.5 mg L-1 of lindane, and lindane concentrations in the media decreased. N. oculata removed 73% and 68.2% of lindane in the 0.1 and 0.5 mg L-1 media concentrations, respectively. Algal biomass decreased to the level of the control at lindane concentrations greater than 2.5 mg L-1, probably due to toxicity. N. oculata removed lindane from the media at concentrations lower than 1.0 mg L-1. Thus, N. oculata may be useful for lindane bioremediation in contaminated aquatic systems.