In co-cultureR. mucilaginosa with M. purpureus spores promoted the growth and ca-rotenoids yield of R. mucilaginosa. Several factors influenced thebiosynthesis of carotenoids in yeast, with the most commonly knownbeing the carbon to nitrogen ratio (C/N ratio) and the level of dissolvedoxygen (DO). Appropriate C/N ratio and above 20% of the DO level havebeen associated with an increase in carotenoid production but a decrease was observed after the optimal pointwas exceeded. The C/N ratio and the DO level affected carotenoids biosynthesis and not the growth of R. mucilaginosa.