Otimização do cultivo de chlorolobion braunii em associação de concentrado salino e água salobra: um bioprocesso para obtenção de biomassa e produção de biodiesel

Abstract

Effluents used as a culture medium for microalgae represent a strategy that combines wastewater treatment—promoting nutrient removal—with the generation of high value-added biomass. The ability of microalgae to accumulate lipids and carbohydrates in their biomass makes them a promising source for biofuel production. The aim of this study was to optimize the production and characterize the biomass of the microalga Chlorolobion braunii using a combination of brackish water and saline concentrate, a condition not previously explored. In addition, the potential of this biomass for biodiesel production was evaluated. The experiments were carried out in Erlenmeyer-type bioreactors (1 L), and the best biomass production condition was determined using a central composite rotational design with the following factors: volume of saline concentrate in brackish water (0–100%) and urea concentration (0.00– 0.08 g/L). The optimized condition was defined as 36.6% saline concentrate, 63.4% brackish water, and 0.02 g/L urea. The best treatment was the experiment with 50% brackish water and 50% saline concentrate, which produced 0.556 g/L of biomass with an average productivity of 0.014 g/L/day, and high levels of biomolecules such as 21.14% carbohydrates and 29.40% lipids. It also achieved bioremediation of 86.25% of nitrates (NO₃⁻), 79.17% of phosphates (PO₄³⁻), and a 23.18% reduction in salinity. The biomass showed high fatty acid content, with 24.94% C16:0 (palmitic acid) and 38.44% C18:1n9c (oleic acid), producing biodiesel that meets the quality standards of the American Society for Testing and Materials (ASTM D6751) and the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP). This study optimized the biomass production of Chlorolobion braunii and demonstrated the feasibility of using only a combination of brackish water and saline concentrate—without prior treatment and without the addition of synthetic medium—resulting in high levels of biomolecules that can serve as feedstock for the generation of high value-added bioproducts.