Effect of trace metals on growth performance and accumulation of lipids, proteins, and carbohydrates on the green microalga Scenedesmus obliquus

Microalgae biomass is considered one of the most promising raw materials for the development of high commercial value products, mainly because they are potential sources of proteins, lipids, carbohydrates, and vitamins. In this way, the optimization of culture medium of these microorganisms can help to reduce production costs, making final products more accessible. In this sense, the present study aimed to investigate the effect of different trace metal concentrations on growth and biochemical composition of Scenedesmus obliquus. Cultures of S. obliquus were performed using the LCA-AD medium (pH 7.6), in 2-L cylindrical borosilicate glass flasks that were constantly stirred by bubbling 0.7% CO2 enriched air (v/v), irradiance ranging from 520 to 1200 μmols m−2 s−1, and temperature at 22 ± 1 °C. Four trace metal concentrations were tested: control (standard concentration used on Bold’s Basal Medium), ten (10−1), hundred (10−2), and thousand (10−3) times less than control. The trace metal concentration did not significantly affect the growth of S. obliquus – all treatments have reached about 4.2 g L−1 on the tenth day of cultivation. As well for growth performance, no significant differences were observed among the treatments for biomass composition percentages. The dry S. obliquus biomass was mainly composed of carbohydrates (about 65%), crude protein (about 20%), and finally lipids (about 12%). These findings suggest that up to 1000-fold reduction in trace metal concentration does not affect the growth and biochemical composition of the green microalga S. obliquus.