Interactive effects of chromium stress and essential micronutrient availability on biomass productivity and phycocyanin production in Limnospira platensis: from controlled cultivation to pilot-scale

Phycocyanin (C-PC) is a high-value pigment with significant potential in the food, cosmetic, and nutraceutical industries. However, improving C-PC accumulation while maintaining biomass productivity under large-volume cultivation conditions remains challenging. This study investigated the influence of essential nutrient supplementation alongside targeted chromium (Cr) stress on the biomass production and phycocyanin dynamics of Limnospira platensis CCATMU under large-volume greenhouse cultivation conditions. volumes in 3,000-L-capacity culture ponds under nine predefined treatment conditions involving essential nutrients and Cr stress. C-PC was extracted using ultrasound-assisted extraction (UAE) followed by stepwise ammonium sulfate fractionation and dialysis. The antioxidant activity (DPPH assay), purity index, and acute toxicity ( Artemia salina assay) were evaluated. Findings revealed a distinct decoupling between biomass accumulation and C-PC biosynthesis. Low-level chromium exposure (0.1 mg L⁻¹) appeared to function as an upstream metabolic trigger, leading to an enhancement in C-PC quality, characterized by a maximal purity index of 4.82 and elevated accumulation levels. In contrast, the higher combined micronutrient and chromium treatment was associated with reduced growth. The purified pigment exhibited robust antioxidant activity (IC₅₀: 312.8 µg mL -1 in methanol) and in A. salina , mortality remained below 5% across the tested concentrations, and 50% mortality was not reached within the tested range. Chromium supplementation was associated with increased C-PC accumulation under the tested large-volume greenhouse conditions, although the underlying mechanisms and scalability of this response require further investigation. These findings suggest that such an approach may offer a potential framework for the industrial-scale production of high-purity phycocyanin, warranting further investigation for nutraceutical applications.