Biosynthesis of Carotenoids in Plants and Microorganisms

Carotenoids are secondary metabolites chemically classified as fat-soluble tetraterpenes. These compounds are produced by both photosynthetic organisms, including plants and microalgae, and non-photosynthetic organisms, such as bacteria and fungi. Carotenoids come in various colors, ranging from red hues to orange and yellow. These colors derive from at least six conjugated double bonds in a polyene chain. Carotenoids also display several key biological activities, particularly antioxidant, anticancer and anti-inflammatory activities, and various applications as food colorants, as dietary supplements in formulations, such as tablets and oils, as nutraceuticals and cosmetics, and even as feed for fish and crustaceans. Due to these biological activities and applications, the demand for carotenoids has been increasing, triggering the search for optimizing the production of these compounds from natural and clean sources, especially on an industrial scale. The aim of this study is to gather recent data on carotenoids, highlighting their main biological activities, classification and nomenclature, the reactions involved in the biosynthesis of these compounds, the main carotenoids found in plants and microorganisms, and the formation of vitamin A derivatives from carotenoids, which are essential for eye health.