Luminosity and Chemical Stress Improve the Production of Biomass and Biomolecules from Chlorella vulgaris Cultivated in Produced Water

Produced water (PW) is an effluent from the petrochemical industry that has a significant environmental impact due to its high salinity and presence of chemical compounds and heavy metal. Microalgae have been considered promising to phytoremediation of this effluent and producing biomass with high added value. Therefore, this study aimed to stimulate the production of biomass and biomolecules from Chlorella vulgaris by supplementation with PW and evaluate the synergistic effect of sources of physical and chemical stress. C. vulgaris was cultivated in different PW concentations of PW (not autoclaved) and BG11 medium under a 24 h photoperiod, with inoculum pre-adapted the same photoperiod. The culture containing 70% of BG11 and 30% PW (PW 30%) was the most viable, with a biomass production of 1.35 g/L and a higher concentration of carbohydrates (37.46%) and ash (18.21%) than the control culture (100% BG11). Furthermore, PW 30% also resulted in considerable amounts of lipids (9.92%), proteins (21.94%), chlorophyll-a (6.64 mu g/mL), chlorophyll-b (10.57 mu g/ mL), and carotenoids (21.38 mu g/mL). The major fatty acids were C18:3n6 (21.50%), C20:0 (19.96%), C16:0 (17.12%), and C18:0 (12.15%). The PW 30% treatment showed removal efficiencies for iron (61.80%), chlorides (79.64%), phosphates (97.18%), and petroleum hydrocarbons including total petroleum hydrocarbons (TPH; 45.39%) and resolved petroleum hydrocarbons (RPH; 57.57%). The analyzed fuel properties presented an ideal profile for the production of biodiesel and bioethanol, which can be obtained from carbohydrates. Simultaneously, treatment PW 30% resulted in the production of biomolecule-rich in biomass in addition to the bioremediation effect.