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The biosynthesis of commercialized carotenoids (e.g., lycopene, β-carotene, zeaxanthin, and astaxanthin) using recombinant microorganisms is one of the reasonable and cost-effective alternatives to extraction from natural sources and chemical synthesis. Among heterologous hosts, Escherichia coli is one of the most useful and manageable. To date, many approaches using recombinant E. coli are available to produce various carotenoids. Here we outline the latest carotenoid production research using recombinant E. coli produced through pathway engineering and its future prospects.Nowadays, carotenoid biosynthetic pathways are sufficiently elucidated at gene levels in bacteria, fungi, and higher plants. Also, in pathway engineering for isoprenoid (terpene) production, carotenoids have been one of the most studied targets. However, in 1988 when the author started carotenoid research, almost no carotenoid biosynthesis genes were identified. It was because carotenogenic enzymes are easily inactivated when extracted from their organism sources, indicating that their purification and the subsequent cloning of the corresponding genes were infeasible or difficult. On the other hand, natural product chemistry of carotenoids had advanced a great deal. Thus, those days, carotenoid biosynthetic pathways had been proposed based mainly on the chemical structures of carotenoids without findings on relevant enzymes and genes. This chapter shows what happened on carotenoid research, when carotenoid biosynthesis genes met non-carotenogenic Escherichia coli around 1990, followed by subsequent developments.Actinobacteria is the phylum that has the biggest genome in the Bacteria domain and includes many colored species. Their pigment analysis revealed that structurally diverse carotenoids are responsible for their pigmentation. This chapter reviews the biosynthesis of the diverse carotenoids of Actinobacteria. Its carotenoids belong to three different types 1) carotenoid of C50 chain length, 2) carotenoids with aromatic end groups, and 3) keto carotenoid like canthaxanthin (β,β-carotene-4,4′-dione) or monocyclic keto-γ-carotene derivatives. Species from the genus Rhodococcus are the only known Actinobacteria with a simultaneous pathway to aromatic and to keto carotenoids.Haloarchaea are halophilic microorganisms belonging to the Archaea domain that inhabit salty environments (mainly soils and water) all around the world. Most of the genera included in this group are able to produce carotenoids at significant concentrations (even wild-type strains). The major carotenoid produced by the cells is bacterioruberin (and its derivatives), which is only produced by this kind of microbes. Nevertheless, the understanding of carotenoid metabolism in haloarchaea, its regulation, and the roles of carotenoid derivatives in this group of extreme microorganisms remains mostly unrevealed. Besides, potential biotechnological uses of haloarchaeal pigments are poorly explored. This work summarizes what it has been described so far about carotenoid production by haloarchaea, haloarchaeal carotenoid production at large scale, as well as the potential uses of haloarchaeal pigments in biotechnology and biomedicine.Oleaginous yeasts, Yarrowia lipolytica and Lipomyces starkeyi, can synthesize more than 20% of lipids per dry cell weight from a wide variety of substrates. This feature is attractive for cost-efficient production of industrial biodiesel fuel. These yeasts are also very promising hosts for the efficient production of more value-added lipophilic compound carotenoids, e.g., lycopene and astaxanthin, although they cannot naturally biosynthesize carotenoids. Here, we review recent progress in researches on carotenoid production by oleaginous yeasts, which include red yeasts that naturally produce carotenoids, e.g., Rhodotorula glutinis and Xanthophyllomyces dendrorhous. Our new results on pathway engineering of L. starkeyi for lycopene production are also revealed in the present review.Xanthophyllomyces dendrorhous (with Phaffia rhodozyma as its anamorphic state) is a basidiomycetous, moderately psychrophilic, red yeast belonging to the Cystofilobasidiales. Its red pigmentation is caused by the accumulation of astaxanthin, which is a unique feature among fungi. The present chapter reviews astaxanthin biosynthesis and acetyl-CoA metabolism in X. dendrorhous and describes the construction of a versatile platform for the production of carotenoids, such as astaxanthin, and other acetyl-CoA-derived compounds including fatty acids by using this fungus.Eukaryotic microalgae and prokaryotic cyanobacteria are diverse photosynthetic organisms that produce various useful compounds. Due to their rapid growth and efficient biomass production from carbon dioxide and solar energy, microalgae and cyanobacteria are expected to become cost-effective, sustainable bioresources in the future. These organisms also abundantly produce various carotenoids, but further improvement in carotenoid productivity is needed for a successful commercialization. Metabolic engineering via genetic manipulation and mutational breeding is a powerful tool for generating carotenoid-rich strains. This chapter focuses on carotenoid production in microalgae and cyanobacteria, as well as strategies and potential target genes for metabolic engineering. Recent achievements in metabolic engineering that improved carotenoid production in microalgae and cyanobacteria are also reviewed.In higher plants, there are many studies on carotenoid biosynthetic pathways and their relevant genes. On the other hand, few researches exist on carotenoid biosynthesis in early-land plants containing liverworts, mosses, and ferns. this website Thus, the evolutionary history of carotenoid biosynthesis genes in land plants has remained unclear. A liverwort Marchantia polymorpha is thought to be one of the first land plants, since this plant remains a primitive figure. Moreover, this liverwort is regarded as the model plant of bryophytes due to several reasons. In this chapter, we review carotenoid biosynthesis in liverworts and discuss the functional evolution and evolutionary history of carotenogenic genes in land plants.