Multivariable optimization process of heterotrophic growth of Chlorella vulgaris

Abstract

Microalgae have received increasing attention as one of the most promising feedstocks in the development of new healthier food products and different strategies have been attempted to improve their growth. However, the high production costs and low productivities, commonly associated with photoautotrophic growths, are still a big challenge. In this study, a two-step optimization strategy was carried out in order to maximize the biomass production of a Chlorella vulgaris strain used at industrial scale under heterotrophic conditions. From a total of 24 independent variables, which were studied simultaneously, 10 have presented a positive effect over Xmax, while the remaining have shown to be negative. The amount of (NH4)2SO4 (6.3 g L−1), MgSO4·7H2O (0.7 g L−1), and C6H12O6 (50% w/v) in the culture medium has revealed to be the only factors with a significant impact on biomass concentration, with optimum values of 25.5, 64.6, and 75 ml.L−1, respectively. The optimized medium resulted in an improvement of the Xmax by 99.6% when compared to the growth medium applied at industrial scale, proving the success of this strategy. Additionally, the carbohydrates production was enhanced by 48.0%.