Microalgae-derived bioactive compounds: metabolic potential, extraction strategies, and sustainable applications in food, pharmaceuticals, and animal feed

This paper critically reviews how the metabolic potential of microalgae can be harnessed for the food, pharmaceutical, and animal feed industries by integrating cultivation system design with green extraction technologies, emphasizing their combined impact on bioactive compound yield, quality, and sustainability. These metabolites, including proteins (up to 60% dry weight in Spirulina), pigments (14–20 mg g‒1 chlorophyll in Chlorella), polyunsaturated fatty acids such as EPA (20–30% of total lipids), antioxidants, and polysaccharides, offer high nutritional and therapeutic potential. These values represent relatively high productivities reported under optimized laboratory or pilot-scale cultivation conditions, cultivation system, and environmental parameters. Cultivation strategies play a crucial role in determining both productivity and metabolite profiles. Recent metabolomic and biochemical studies reveal that parameters such as pH, temperature, and light intensity strongly influence lipid and pigment biosynthesis. For instance, Chlorella vulgaris and Nannochloropsis oculata achieved lipid productivities of 69.46 and 192.3 mg l‒1 day‒1, respectively, in optimized photobioreactors, while Dunaliella salina exhibited enhanced β-carotene accumulation under controlled light and nutrient conditions. Comparative studies indicate that such improvements are generally greater in closed systems than in open systems due to enhanced environmental control and reduced variability. For instance, closed photobioreactors enhance lipid accumulation and metabolic control, with Haematococcus pluvialis achieving 1.27 ± 0.03 g m‒2 day‒1 astaxanthin productivity and 3.9 ± 0.2% dry weight under nitrogen limitation, whereas open pond systems typically show lower and more variable yields (≤ 0.3–0.6 g m‒2 day‒1) due to limited environmental control. Extraction of these bioactives utilizes both conventional (50–80% yield) and green methods, such as supercritical CO2 extraction (up to 90% yield), that improve efficiency and sustainability. Overall, this review highlights how cultivation system design and green extraction innovations drive the efficient and eco-friendly production of high-value microalgal bioactive compounds.