Unexplored potential of brine-derived salts in microalgal bioprocess for enhanced astaxanthin yield and sustainable biorefinery
摘要
Salt-induced astaxanthin production shows significant promise, yet detailed studies on specific salt effects remain limited, especially in complex salt systems. This study developed a two-stage mixotrophic bioprocess in Chromochloris zofingiensis to maximize astaxanthin production utilizing various salts found in brine from desalination and industrial effluents. Among the salts tested, NaCl at 1 g L−1 yielded the highest biomass (3.29 g L−1) and astaxanthin content (21.4 mg g−1). Further astaxanthin enhancement was achieved by combining salt stress with nitrogen deficiency, with NaCl and CaCl₂ yielding 25.14 and 24.33 mg g−1, respectively. Individually, Mg2⁺ was most effective for biomass production (3.53 g L−1), whereas Na⁺ and Ca2⁺ improved astaxanthin biosynthesis, encouraging the exploration of salt combinations. Optimal astaxanthin synthesis (31.41 mg g−1) and yield (87.10 mg L−1) occurred with a NaCl-CaCl₂ combination. Red light exposure further increased biomass and astaxanthin content to 2.83 g L−1 and 28.78 mg g−1, respectively. Elevated Na⁺ induced oxidative stress, countered by promoting astaxanthin production, while Ca2⁺ supported synthesis through cellular signaling pathways. Mg2⁺, essential for chlorophyll, indirectly boosted astaxanthin production by enhancing light absorption. These findings suggest that C. zofingiensis can be a commercially viable source of astaxanthin within a sustainable biorefinery model, aligning with Sustainable Development Goals 9 (Industry Innovation) and 12 (Responsible Consumption and Production).
Graphical Abstract