Influence of nutrients on biomass and oil yield from microalgae Chlorella vulgaris for biodiesel production

Abstract

Microalgae are commonly used in aquiculture as feed for postlarval mollusks, fish and crustaceans because they are easy to grow, small in size, grow rapidly and have high levels of fatty acids. These microorganisms also accumulate high amounts of oil, which can be extracted and converted into biodiesel using chemical processes. In this work, freshwater microalgae Chlorella vulgaris was grown in the Live Food Production Laboratory (LABPAV/IFCE Aracati Campus), with urea (stock solution 1), triple superphosphate (stock solution 2) and vitamins (stock solution 3), in growth medium, in triplicate, using three different quantities of stock solutions 1 and 2, but with a constant amount of vitamins. The quantities of 0.5, 1 and 2 mL (T0.5, T1 and T2, respectively) were used for both stock solutions. We then monitored the growth of the microalgae, flocculated through chemical flocculation by adding a NaOH 2N solution, air-oven dried at 60 ºC for 24 hours, weighed the dried biomass on a semi-analytical balance, and extracted the oil using solvents. We thus observed that algal growth intensified and dry biomass increased as the amount of nutrients increased in the growth media; inversely, the best oil level was observed in the treatment using the lowest amount of nutrients in the growth media where the microalgae developed (20.13±0.19%). Finally, in Treatment T2, even with the lowest percentage of oil (18.95%), the amount of biomass produced compensates in the oil productivity, and using a lower amount of nutrients in the media of culture.