Fig. 2

Metabolic engineering of X. dendrorhous for overproduction of carotenoids. A Representation of knock-in and knock-out strategies for genetic engineering in yeast. B Overexpression of HMG1, crtE and crtYB for high production of phytoene [58]. C Genetic engineering of X. dendrorhous for high yield astaxanthin production. Integration of multiple copies of crtYB and crtS to increase the production of β-carotene and its conversion to astaxanthin, respectively [33, 89]. D Metabolic engineering and conventional mutagenesis for high yield astaxanthin production [66]. crtYB and crtS genes were integrated using geneticin (G418) and hygromycin (hph) as selection markers. Afterwards, a random chemical mutagenesis was carried out using 200 µg/mL NTG. Chemical mutagenesis was repeated several rounds until the maximal astaxanthin overproducer was obtained. The best strain obtained, AXJ-20/crtYB, was able to yield above 9.7 mg/g of dry biomass