## 4 Concurrent Development of Value-Added Products Beneficial to Human and Animal Health
### Commercially Available Products  
The precursor to vitamin A, beta-carotene, is a useful natural food coloring and part of a balanced diet. It is also a necessary nutrient and possesses antioxidant qualities. It is lipophilic and non-polar, and soluble in carbon disulfide, benzene, and chloroform, but insoluble in water, acids, and alkalis. Every year, 8.5-30% of the beta-carotene needed for human consumption worldwide is produced commercially from the salt-tolerant microalgae _Dunaliella salina_. The market for beta-carotene reached USD 334 million globally in 2018. Australia, Israel, India, and China are experiencing an increase in beta-carotene production and commercial activity [2]. A natural source of pigments with antioxidant qualities and benefits for human health is the recombinant protein astaxanthin, a type of carotenoid. Specifically, it helps treat resistance to infections, coronary heart disease, and skin cancer. By 2020, the astaxanthin market is expected to grow to a value of USD 1.1 billion globally. When heated, astaxanthin dissolves in acetone, acetic acid, chloroform, pyridine, and DMSO. It is also polar and lipophilic. Astaxanthin can be accumulated by a variety of microalgae, including different strains of _Chloerella_. However, _Haematococcus pluvialis_, which is grown in indoor and outdoor PBRs or hybrid PBR systems for infection control, is the primary source used in its commercial production [2]. Astaxanthin, unlike other carotenoids, is not a precursor to vitamin A. Its synthesis for commercial purposes is undertaken using petrochemical raw materials, but this makes it prohibitive for human consumption, as defined by the FDA, and thus enhances the need for natural astaxanthin production. Microalgae that produce astaxanthin as a secondary metabolite are an increasingly important source of natural production, the most important being _Haematococcus pluvialis_. Its cells accumulate the highest amount of astaxanthin, which makes up 90% of all its carotenoids and can reach 7% on dry biomass ([PERSON] et al. [29]). Beta-carotene and astaxanthin show strong demand growth in the market. The commercial value of carotenoids was anticipated to increase at an annual growth rate of 3.5% from 2016 to 2021, reaching revenues of EUR 1.52 billion, according to forecasts made by Zion Market Research Global in 2016. By 2021, it was anticipated that astaxanthin and beta-carotene would account for 25% and 26% of the market, respectively. The microalgae _Haematococcus pluvialis_ and _Dunaliella salina_ are promising sources of carotenoids for industrial processing due to their ability to accumulate carotenoids, and because of the projected increase in market demand [29]. Fish oils contain eicosapentaenoic acid (EPA), an omega-3 fatty acid with positive effects on human health. The global market for omega-3 fats was valued at USD 34.7 billion in 2016. Fish oil is the primary source of EPA, but Nannochloropsis species offer a promising substitute because, depending on growing conditions, they may produce EPA at levels of 1.1-12% dry weight. Commercially, Nannochloropsis sp. are grown photo-autotrophically in tanks with natural light and CO\({}_{2}\) from power plants, but heterotrophic or mixotrophic cultures can be grown at the pilot or small stage [2]. It is also possible to add microalgae as a feed supplement. Because it has been shown to be advantageous to animal physiology, the species Arthospira, in particular, is used as feed for aquarium fish, cattle, cats, dogs, horses, and shellfish. Although there are drawbacks, microalgae are also utilized as a source of protein in poultry feed, although not in higher concentrations or for extended periods of time. The primary side effects of feeding microalgae to poultry are changes in the skin and egg yolk colors. Over 50% of _Arthospira_ cultivation is grown for feed supplement production, and 30% of algae production worldwide is used to produce animal feed [21].