The carotenoids market in 2019/2020 is supposed to reach $1.5-1.8 billion with a compound annual growth rate of 3.9% [13; 14] and due to the extensive commercial and industrial uses of carotenoids (mainly lutein and astaxanthin), the demand of these compounds is high around the world. Therefore, several biological platforms are used for the biotechnological production of natural carotenoids for their use in food and feed, cosmetics, and the chemical and pharmaceutical industries [15].  
One of these platforms is the red/pink-pigmented heterobasidiomycetous yeast _Xanthophyllomyces dendrorhous_ (the teleomorphic state of _Plaffia rhodozyma_), which was isolated in the late 1960s from tree-exudates in Japan and Alaska [16] and naturally produces and accumulates the xanthophyll astaxanthin [17]. This yeast can be considered as a cell-factory for the production of industrially valuable carotenoids [18], since the genome of _X. dendrorhous_ CBS6938 has been sequenced [19] and biotechnology tools for the genetic manipulations of this microorganism are available [20; 21; 22; 23]. In addition, this yeast does not require light for accumulation of astaxanthin, is able to metabolise many kinds of saccharides under both aerobic and anaerobic conditions, and reproduces at relatively high growth rates [24]. Besides, its approval as a colour stabiliser for fish feed supplementation by FDA (U.S. Food and Drug Administration) supports the natural production as an interesting methodology ([[https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=73.355](https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=73.355)]([https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=73.355](https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=73.355))).  
In addition to astaxanthin, _X. dendrorhous_ is able to produce several carotenoids, including \(\beta\)-carotene, canthaxanthin, zeaxanthin, and astaxanthin via mevalonate pathway (Figure 1). \(\beta\)-carotene, a red-orange carotenoid, possesses \(\beta\)-rings at both ends and serves as an intermediary molecule for the biosynthesis of astaxanthin [25; 26]. This compound is widely used in the food, feed, cosmetic, and pharmaceutical industries due to its potent colouring traits, antioxidant properties, and provitamin A activity, since it appears to be the most important vitamin A precursor for vertebrate animal species [27]. Besides, \(\beta\)-carotene adds colour to beverages, dairy products, confectionery, and many other commodities, and together with astaxanthin, they are the most important carotenoids from a commercial point of view. The orange-red pigment canthaxanthin (\(\beta\),\(\beta\)-carotene-4,\(A^{\prime}\)-dione) is a xanthophyll with antioxidant properties widely used in aquaculture and poultry farming, providing the characteristic colour to fish flesh, chicken skin, and egg yolk [28; 29]. Zeaxanthin (\(\beta\),\(\beta\)-carotene-3,\(3^{\prime}\)-diol) is a yellow xanthophyll alcohol important for vision, since together with lutein and meso-zeaxanthin, they are present in high concentrations within the oval-shaped macular pigmented area near the centre of the retina of the eye [30; 31], thus playing an important protective role against several eye diseases [32]. Astaxanthin (3,\(3^{\prime}\)-dihydroxy-\(\beta\),\(\beta\)-carotene-4,\(A^{\prime}\)-dione) is a red-orange pigment with a market value ranging from $2500-7000/kg whose global market was valued at US$447 in 2014 and expected to reach a value of US$1.1 billion by 2020 [14; 33]. After \(\beta\)-carotene, astaxanthin is the second most important carotenoid, representing about 29% of total carotenoid sales [34]. This pigment has strong antioxidant properties and is used as a feed additive in salmon and trout aquacultures as well as in chicken and quail farming and egg production [6; 35; 36].