Balancing growth and oxidative defences in Tetraselmis chuii via manipulation of environmental stressors: modulating superoxide dismutase and catalase activity.

Antioxidant-enriched microalgae hold promise for nutraceutical, pharmaceutical, and aquaculture applications; however, cultivation strategies that balance growth with robust oxidative defenses remain species-specific. Large-scale utilization is often constrained by inconsistent biomass production and variable antioxidant activity, highlighting the need to identify optimal cultivation parameters. This study investigated how environmental stressors (pH, temperature, aeration rate, and light intensity) affect biomass accumulation and antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT) in Tetraselmis chuii under photoautotrophic batch culture. One-factor-at-a-time (OFAT) screening was employed across practical ranges: pH (5.5-8.5), temperature (25-35℃), aeration rate (0-1.5 L/min), and light intensity (46-370 µmol photons m⁻² s⁻¹). Cultures were maintained for 21 days under each condition before analysis. All factors significantly influenced both biomass and antioxidant production. Optimization through OFAT (pH 7.5, 30℃, 1.0 L/min, 92 µmol photons m⁻² s⁻¹) increased biomass production 1.24-fold to 538.0 mg/L while enhancing CAT activity to 489.19 U/g and maintaining SOD activity at 1009.04 U/g. In contrast, pre-optimization conditions (pH 7.5, 25℃, 0.25 L/min, 92 µmol photons m⁻² s⁻¹) yielded lower biomass (432.32 mg/L) and CAT activity (266.97 U/g), though SOD activity remained comparable (1022.30 U/g). These findings demonstrate how controllable environmental stressors can be manipulated to enhance both SOD and CAT production while sustaining T. chuii growth, supporting the development of antioxidant-enriched microalgal biomass production processes. Future research should explore photobioreactor scale-up, combined stressor effects, and genetic engineering approaches to further optimize yields for industrial applications.