Otimizações operacionais do cultivo de microalgas em água produzida da indústria do petróleo visando o seu tratamento e reuso em um processo de produção de bioativos

Abstract

Produced water (PW) from the oil industry represents a significant environmental challenge due to its high salinity and complex chemical composition. Sustainable treatment of this effluent is essential to reduce environmental impacts and enable its reuse. Microalgae, such as Dunaliella salina, stand out as a biotechnological alternative for PW remediation, while also allowing the production of high-value biocompounds such as lipids and pigments. This study evaluated the effects of alternating electric current and different light spectra on the growth, biomass production, and accumulation of lipids and pigments in D. salina cultivated in PW and synthetic medium. Different electric current intensities (50, 750, and 990 µA) and frequencies (1, 50, and 100 Hz), as well as LED lighting with different wavelengths (red, blue, pink, and white) at a light intensity of 3,800 lux, were tested. The results showed that applying 50 µA at a frequency of 1 Hz, once a day for 30 minutes, in Conway medium with 8.5% salt salinity, promoted a 92% increase in specific growth rate. The highest biomass accumulation (70%) was observed in Conway with 3.5% salts, under electric stimulation of 50 µA at 1 Hz, once a day for 30 minutes. The intermittent treatment (5 minutes on and 5 minutes off), using 750 µA of alternating current at 1 Hz in Conway 3.5% salts, resulted in a 104% increase in lipid production. PW also showed positive effects under electrical stimulation. At 8.5% salinity, biomass production increased by 23% when applying 990 µA twice a day for 30 minutes. Meanwhile, an intensity of 50 µA applied once a day for 30 minutes led to a 66% lipid accumulation. Light stimulation also had positive impacts on D. salina: under red LED light, there was a 62% and 34% increase in specific growth rate and biomass production, respectively, and blue LED light stimulated lipid production by approximately 205%. These findings highlight the potential of combining electrical and light stimuli to optimize D. salina cultivation, contributing to sustainable bioprocesses and enhancing the feasibility of using PW as a culture medium in biotechnological applications.