Simultaneous production of astaxanthin and lipids from Chlorella sorokiniana in the presence of reactive oxygen species: a biorefinery approach

The current study aimed to investigate the concurrent production of astaxanthin and lipids using Chlorella sorokiniana under mixotrophic conditions in an external loop airlift photobioreactor (ELAPB). Supplementation of Fe2+ into the media in the red phase (stress phase) induced the astaxanthin production. The maximum yield of 154.36 mg L−1 was obtained by the end of the red phase, which is equivalent to 3.4% of the dry biomass weight. The role of reactive oxygen species in the formation of astaxanthin, which protects the microalgal cells from different oxidative stress, has been elucidated. Apart from astaxanthin, unsaturated fatty acids (81.34%) were also produced with excellent biodiesel properties. Unsaturated fatty acids viz., palmitoleic acid (16:1), have resulted in high yields (22.85%), followed by linoleic acid (18:2), 28.27%; oleic acid (C18:1), 14.38%; and eicosapentaenoic acid (20:5), 4.49%. Hence, the simultaneous production of high value-added products, viz., astaxanthin, and lipids makes the whole process economically viable and environmentally sustainable and elevates the commercial potential during scale-up. The astaxanthin radical scavenging activity was also assessed by H2O2 assay, and the maximum scavenging activity was determined as 91%. The study confers the potential advantages of algal cultivation for high-value commercial product synthesis towards additional revenue generation and development of an efficient microalgae-based biorefinery process.