Optimization of the production of lipids and carotenoids in the microalga Golenkinia aff. brevispicula

Abstract

Microalgae are a promising platform to produce natural pigments and lipids when compared to traditional sources, since they present faster growth and biomass productivity and there is a wide diversity that has not been studied yet. The green microalgae belonging to the genus Golenkinia presents few reports of its biomass production and applications. In this work, the productivity of lipids and carotenoids was studied in the strain Golenkinia aff. brevispicula FAUBA-3 using a two-stage cultivation system: a first step for biomass production under semicontinuous cultures, and a second step for the accumulation of lipids and carotenoids under batch salinity stress (35 g L−1). The highest biomass productivity (0.92 g L−1 day−1) was obtained under a dilution rate of 0.4 day−1. The growth rate (μ) was a hyperbolic function of average irradiance inside the culture (Eav). The optimum Eav was 88.4 μmol photons m−2 s−1 and the maximum specific growth rate (μmax) was 0.85 day−1. Photoinhibition was observed above 570 μmol photons m−2 s−1 of Eav. The best photosynthetic performance was obtained at 0.2 day−1 dilution rate but with lower biomass productivity due to nutrients and light limitation. High content of protein (30% DW) and polyunsaturated fatty acids (50% of total PUFAs) and low content of carbohydrates (19% DW) were observed at high dilution rate, and the opposite response at low dilution rate. In the second culture stage, an increase of salinity induced lipid and carotenoid accumulation which improved the productivity to 89 mg L−1 day−1 and 1.3 mg L−1 day−1 of total lipids and carotenoids respectively compared to one-stage culture. Lutein, β-carotene and astaxanthin were the main carotenoid identified in a decreasing order. Those results confirm that two-stage culture is an adequate strategy to optimize the carotenoid and lipid productivity in the promising strain Golenkinia FAUBA-3.