Optimization of Culture Conditions for High Cell Productivity and Astaxanthin Accumulation in Vietnam’s Green Microalgae Haematococcus pluvialis HB and a Neuroprotective Activity of Its Astaxanthin

Abstract

Background: Haematococcus pluvialis, a green microalga, is a rich source of natural astaxanthin and a potent antioxidant with high commercial value. This study investigates the biological characteristics and potential of H. pluvialis HB isolated from Hoa Binh, Vietnam, for growth and astaxanthin accumulation using a two-phase culture method. Methods: H. pluvialis HB was cultured in a C/RM medium at 25 °C, and morphological characteristics were examined. NMR spectroscopy was used to determine the structure of the astaxanthin, which was extracted using the Soxhlet method. Results: After 22 days, the highest cell density (4.96 × 106 cells mL−1) was achieved under optimized light and ultraviolet conditions. Nutrient deprivation followed by bicarbonate supplementation resulted in a maximal astaxanthin accumulation of 48.8 mg g−1 dry cell weight within two days. The extracted astaxanthin demonstrated potent antioxidant activity (IC50: 3.74 mg mL−1) compared to ascorbic acid (IC50: 18.53 µg mL−1) and exhibited strong acetylcholinesterase inhibition (IC50: 297.99 µg mL−1). It also showed neuroprotective effects against H2O2 and amyloid beta-induced neurotoxicity in C6 cells. Conclusions: This study highlights H. pluvialis HB as a promising source for large-scale astaxanthin production with potential applications in neuroprotective health products.