Growth and Metabolite Production in Chlorella sp.: Analysis of Cultivation System and Nutrient Reduction

Microalgae are a sustainable source for many bioproduct syntheses. This study shows how different cultivation systems and nutrient concentrations affect Chlorella sp. development. The cultivation was performed in open and closed lab-scale systems. A Tukey test was used to evaluate the significant differences between the microalgae growth and composition under the two systems analyzed. The effect of nitrogen and phosphorus concentration was analyzed with a 22 full factorial design. Lipids, carbohydrates, proteins, and pigments were extracted and quantified. The highest specific growth rate (0.52 1/day) was obtained in the open pond, with a cell density of 5.06 × 107 cells/mL and a biomass concentration of 1.30 mg/mL. In this condition, the higher concentration of pigments was obtained: 13 μg/mg of chlorophyll-a, 15 μg/mg of chlorophyll-b, and 2 μg/mg of carotenoids. An expressive increase in the lipid (from 17 to 35%) was obtained in low nitrogen and high phosphorus. Protein percentage increases with both nutrients at a higher level, reaching up to 60%. The percentage of carbohydrates decreases from 32 to 13% with phosphorus reduction. Thus, this study points out the conditions that benefit the accumulation of each Chlorella sp. metabolite, contributing to the decision-making for the cultivation and applications of this microalgae.