Optimization of semi-continuous cultivation conditions for the improvement of lipid productivity from thermo-tolerant Chlorella vulgaris XJW

Abstract

ABSTRACT Chlorella vulgaris XJW (C. vulgaris XJW), one temperature tolerable microalgae with biodiesel production potential, was selected from Ulungur Lake in Xinjiang. In this research, optimal semi-continuous cultivation conditions were obtained by employing uniform design method. The total biomass and lipid productivity of C. vulgaris XJW cultured with semi-continuous mode in Column photobioreactor were affected by renewal rate, renewal period, nitrogen concentration and phosphorus concentration. According to the regression equation, the optimal semi-continuous cultivation conditions for the total biomass of C. vulgaris XJW was renewal rate of 33%, renewal period of 4 days, NaNO3 concentration of 0.69 g·L−1 and K2HPO4 concentration of 0.02 g·L−1. In the optimal conditions, the maximum total biomass of C. vulgaris XJW was 3.682 g·L−1, which was 20.1% higher than the highest value in unoptimized semi-continuous cultivation conditions, and 2.6 times higher than that in batch cultivation. Meanwhile, the optimal semi-continuous cultivation conditions for lipid productivity of C. vulgaris XJW was renewal rate of 27%, renewal period of 3 days, NaNO3 concentration of 1.03 g·L−1 and K2HPO4 concentration of 0.02 g·L−1. In the optimal conditions, the maximum lipid productivity of C. vulgaris XJW was 110.43 mg·L−1d−1, which was 16.8% higher than the highest value in unoptimized semi-continuous cultivation conditions, and 2.7 times higher than that in batch cultivation. Results were consistent with the predicted values obtained by model equations, which confirmed the reliability of model equations. The models achieved in this work could accurately predict the semi-continuous cultivation conditions of C. vulgaris XJW with total biomass and lipid productivity as indicators. Good cultivation model would make the large-scale cultivation of this kind of microalgae possible, providing enough materials for the biodiesel production.