Effect of nitrogen concentration on the production and composition of Chlorella minutissima biomass in a batch bubble-tank photobioreactor

Abstract

Chlorella minutissima has great potential to be used in a 3G biorefinery, due to its ability to produce a wide variety of high-value compounds, such as proteins, lipids, carbohydrates, and pigments. Nitrogen is one the main macronutrients that control the cellular metabolism, and the variation of its concentration in the culture medium strongly influences the growth and composition of the microalgae. Although studied for different species of microalgae, the effect of nitrogen source concentration can be highly variable dependent on the specie and range of evaluated concentrations, with only a few studies dealing with the specie Chlorella minutissima. This work evaluated the effect of nitrogen concentration on productivity of lipids, and carbohydrates in the biomass during the autotrophic cultivation of the microalga C. minutissima. The experiment was conducted in batch process in a bubble tank photobioreactor, with the nitrate concentration in the medium varying from 37.5 to 150.0 mgL−1. The highest productivity values ​​of biomass, lipids, and carbohydrates were 262.0 ± 4.3, 105.2 ± 1.7, and 36.7 ± 0.6 mg L−1 d−1, respectively, obtained using 150 mgL −1 of nitrate in the medium. Also using this nitrate concentration, about 9% of glucose and 10% of xylose/galactose/mannose were observed in microalgal biomass after lipid extraction. The results obtained from the autotrophic cultivation of C. minutissima can be useful for the production of this microalgae at large scale in a 3G biorefinery. Graphical abstract: (Figure presented.)