Semi-continuous process as a promising technique in Ankistrodesmus braunii cultivation in photobioreactor

Abstract

Microalgae are unicellular and photosynthetic organisms which have great potential for providing various products of interest in the food, chemicals, pharmaceuticals, and cosmetics industry. The green alga Ankistrodesmus braunii has been cited as capable of producing large amounts of lipids. In this sense, this work aims to study A. braunii growth in tubular photobioreactor using different amounts of nitrogen and under different cultivation processes. In batch cultures, the maximum biomass concentration (X_m) was 1588 ± 11 mg L⁻¹ using 20 mM of NaNO₃. A fed-batch process with the addition of 20 mM NaNO₃ each 48 h from the first to the sixth cultivation day reached X_m = 2753 ± 7 mg L⁻¹. The semi-continuous process was effective to eliminate the lag phase, allowing to obtain X_m = 2399 ± 5 mg L⁻¹. In this condition, the protein and lipid levels in the biomass were 33.1 ± 0.2% and 38.6 ± 0.2%, respectively. The maximum specific growth rate (μ_m) reached a maximum value of 0.998 day⁻¹ in the semi-continuous process using 20 mM NaNO₃. The results of this study show the potential for the production in a large scale of A. braunii as a source of protein and lipids for commercial applications.