H2O2-induced enhancement of astaxanthin accumulation in Microcystis aeruginosa.

Astaxanthin is a naturally derived antioxidant with great market value. A huge biomass of cyanobacteria is harvested during water blooms salvage and treatment, of which Microcystis aeruginosa is a typical species with astaxanthin biosynthetic capacity. To promote the high-value utilization of the salvaged cyanobacteria after enhancing their astaxanthin accumulation via H2O2 treatment, the cellular proliferation, reactive oxygen species (ROS) content, photosynthetic performance, astaxanthin biosynthesis, as well as related gene expression in M. aeruginosa were assayed under H2O2 stress. With raising H2O2 concentration, the inhibition on cellular proliferation enhanced gradually, because of the increase of ROS levels and decrease of chlorophyll content and photosynthetic performance. H2O2 treatment increased the levels of astaxanthin along with its precursors, zeaxanthin and β-carotene, by up-regulating 7 genes (crtP, Z-ISO, crtQ, crtH, cruA, cruP, and crtR) involved in astaxanthin biosynthesis, with the maximum accumulation was observed after 2 days. For astaxanthin yield, it showed the strongest correlation with H2O2 concentration and astaxanthin content. Therefore, H2O2 treatment is suitable for improving the high-value antioxidant levels, and a short-term treatment can induce its rapid accumulation.