Microalgal Astaxanthin: From Metabolic Regulation to Industrial Biomanufacturing for a Sustainable Bioeconomy

Astaxanthin is a ketocarotenoid with potent antioxidant properties. It exhibits higher antioxidant activity than several other carotenoids and has potential applications in cosmetics, nutraceuticals, and pharmaceuticals. Microalgae are the primary producers in aquatic ecosystems. They are also regarded as sustainable and promising chassis for a sustainable bioeconomy due to their efficient photosynthesis and ability to convert CO2 into valuable products. However, the current large-scale production of astaxanthin from microalgae is still limited due to critical bottlenecks, including unclear regulatory mechanisms of astaxanthin biosynthesis, suboptimal strain performance and low product titers, resulting in the high cost of phototrophic cultivation and downstream processing. This review summarizes recent studies on the metabolic regulation of astaxanthin biosynthesis and technological advances in industrial biomanufacturing, highlighting how integrated strategies can enable a sustainable bioeconomy. We propose a conceptual and modular framework for a green astaxanthin intelligent manufacturing system, which integrates breeding and metabolic regulation, large-scale cultivation process optimization, green separation, extraction and application. This review would be helpful for upgrading the industrial development of microalgal astaxanthin to the strategic level of supporting global climate change responses, protecting ecological resource security, and promoting the green industrial revolution.