Antioxidant potential of extracts of Chromochloris zofingiensis cultivated in pilot-scale outdoor tubular photobioreactors under nitrogen limitation

Abstract

Chromochloris zofingiensis is known to be able to produce large amounts of astaxanthin and also to coproduce other molecules with antioxidant properties. Outdoor cultivation is the cheapest way for large-scale production; however, the unstable weather conditions can hinder the productivity of the biomass and the target product. The final biomass (0.92 g·L−1) and total carotenoids (0.55 mg·g−1) concentration achieved in outdoor cultivation (i.e., during autumn in Porto, Portugal) had no statistically significant difference compared to control cultivation (i.e., constant temperature, 18 °C, and light intensity, 4000 lx) (1.36 g·L−1 and 0.56 mg·g−1, respectively), however the biomass productivity was about threefold lower. Regarding the antioxidant potential, methanolic extracts from outdoor cultivation presented one of the highest values for radical scavenging ability (44.2 %) and ferrous-ion chelating ability (59.1 %), similarly to the results obtained by ethanolic extracts from indoor cultivation under nitrogen limitation. Highest total antioxidant capacities were observed in ethanolic extracts varying from 120.0 to 185.2 mg GAE·g−1.