NaCl Promotes the Efficient Formation of Haematococcus pluvialis Nonmotile Cells under Phosphorus Deficiency

Accumulation of astaxanthin in Microcystis aeruginosa under NaCl and KCl stresses

Astaxanthin is a high-value natural antioxidant, and can be accumulated in Microcystis aeruginosa. To enhance astaxanthin accumulation in the microalgae by using salt stress, the cell growth, photosynthetic abilities, reactive oxygen species (ROS) levels, astaxanthin and its precursor content, and gene expression were investigated under NaCl and KCl stresses. The two salt stresses inhibited the cell growth by lowering photosynthetic abilities and raising ROS levels. During the 6-day treatment, the two salt stresses improved the levels of astaxanthin, precursors (β-carotene and zeaxanthin) and carotenoids, which might be caused by the raised ROS up-regulating expression of 7 related genes. At the same concentration, KCl stress showed stronger inducing effect on astaxanthin and its precursor production than NaCl stress, due to higher expression of related genes. Therefore, NaCl and KCl stresses have obvious ion differences on astaxanthin accumulation, of which KCl stress is more suitable for the high-value antioxidant production from microalgae.

Astaxanthin: Past, Present, and Future

Astaxanthin (AX), a lipid-soluble pigment belonging to the xanthophyll carotenoids family, has recently garnered significant attention due to its unique physical properties, biochemical attributes, and physiological effects. Originally recognized primarily for its role in imparting the characteristic red-pink color to various organisms, AX is currently experiencing a surge in interest and research. The growing body of literature in this field predominantly focuses on AXs distinctive bioactivities and properties. However, the potential of algae-derived AX as a solution to various global environmental and societal challenges that threaten life on our planet has not received extensive attention. Furthermore, the historical context and the role of AX in nature, as well as its significance in diverse cultures and traditional health practices, have not been comprehensively explored in previous works. This review article embarks on a comprehensive journey through the history leading up to the present, offering insights into the discovery of AX, its chemical and physical attributes, distribution in organisms, and biosynthesis. Additionally, it delves into the intricate realm of health benefits, biofunctional characteristics, and the current market status of AX. By encompassing these multifaceted aspects, this review aims to provide readers with a more profound understanding and a robust foundation for future scientific endeavors directed at addressing societal needs for sustainable nutritional and medicinal solutions. An updated summary of AXs health benefits, its present market status, and potential future applications are also included for a well-rounded perspective.

Biotechnologies for bulk production of microalgal biomass: from mass cultivation to dried biomass acquisition

Microalgal biomass represents a sustainable bioresource for various applications, such as food, nutraceuticals, pharmaceuticals, feed, and other bio-based products. For decades, its mass production has attracted widespread attention and interest. The process of microalgal biomass production involves several techniques, mainly cultivation, harvesting, drying, and pollution control. These techniques are often designed and optimized to meet optimal growth conditions for microalgae and to produce high-quality biomass at acceptable cost. Importantly, mass production techniques are important for producing a commercial product in sufficient amounts. However, it should not be overlooked that microalgal biotechnology still faces challenges, in particular the high cost of production, the lack of knowledge about biological contaminants and the challenge of loss of active ingredients during biomass production. These issues involve the research and development of low-cost, standardized, industrial-scale production equipment and the optimization of production processes, as well as the urgent need to increase the research on biological contaminants and microalgal active ingredients. This review systematically examines the global development of microalgal biotechnology for biomass production, with emphasis on the techniques of cultivation, harvesting, drying and control of biological contaminants, and discusses the challenges and strategies to further improve quality and reduce costs. Moreover, the current status of biomass production of some biotechnologically important species has been summarized, and the importance of improving microalgae-related standards for their commercial applications is noted.

Bioprocess Strategy of Haematococcus lacustris for Biomass and Astaxanthin Production Keys to Commercialization: Perspective and Future Direction

Haematococcus lacustris (formerly called Haematococcus pluvialis) is regarded as the most promising microalgae for the production of natural astaxanthin, which is secondary metabolism used as a dietary supplement, also for cosmetic applications, due to its high anti-oxidant activity. Astaxanthin has a wide range of biological activities and high economic potential, and currently dominates the market in its synthetic form. Furthermore, because of the difficulty of bioprocess and the high cost of cultivation, astaxanthin extracted from this microalga is still expensive due to its low biomass and pigment productivities. Large-scale biomass production in biotechnological production necessitates the processing of a large number of cultures as well as the use of both indoor and outdoor systems, such as open pond raceway systems and photo-bioreactors (PBR). The photo-bioreactors systems are suitable for mass production because growth conditions can be controlled, and the risk of contamination can be reduced to a certain extent and under specific culture parameters. This review discusses current technologies being developed to improve cultivation and operation efficiency and profitability, as well as the effect of parameter factors associated with H. lacustris cultivation on biomass and astaxanthin bioproduction, and even strategies for increasing bioproduction and market potential for H. lacustris astaxanthin.