Metabolism is the sum of cellular chemical and physical activities. It involves chemical changes to reactants and the release of products using well-established pathways regulated at many levels. Knowledge of such regulation in yeasts is crucial for exploitation of yeast cell physiology in biotechnology (Talaro & Talaro, 2001). At controlled cultivation conditions oleaginous red yeasts could be a good source (producer) of lipidic primary metabolites as neutral lipids, phospholipids and fatty acids and ergosterol, which is integrate part of yeast biomembranes.

Secondary metabolism is a term for pathways of metabolism that are not absolutely required for the survival of the organism. Examples of the products include antibiotics and pigments. The induction of secondary metabolism is linked to particular environmental conditions or developmental stages. When nutrients are depleted, microorganisms start producing an array of secondary metabolites in order to promote survival (Mann, 1990). Filamentous fungi and yeasts show a relatively low degree of cellular differentiation, but still they express a complex metabolism resulting in the production of a broad range of secondary metabolites and extracellular enzymes. This very high metabolic diversity has been actively exploited for many years. In terms of biotechnological application fungi and yeast have the advantage of being relatively easy to grow in fermenters and they are therefore well-suited for large-scale industrial production. Biomass enriched by suitable mixture of primary and secondary metabolites can be used too, mainly in feed and food applications (Mann, 1990, Walker 1998).

In general, biosynthesis of individual metabolites is governed by the levels and activities of enzymes employed to the total carbon flux through the metabolic system. Efficiency of that flow depends on the cooperation of individual pathways engaged in this process and which pathway is suppressed or activated varies with the growth medium composition, cultivation conditions, microbial species and their developmental stage. Because overall yield of metabolites is directly related to the total biomass yield, to keep both high growth rates and high flow carbon efficiency to carotenoids by optimal cultivation conditions is essential in order to achieve the maximal metabolite productivity (Certik et al., 2009).