Raw Glycerol and Parboiled Rice Effl uent for Carotenoid Production: Effect of the Composition of Culture Medium and Initial pH

Search for naturally grown food has stimulated the biotechnological production of carotenoids. Therefore, the use of the yeast Xanthophyllomonas dendrorhous has been researched due to its abilities to assimilate different sources as substrates and to produce high amounts of carotenoids. Furthermore, alternative sources have been used as the culture medium to reduce costs and environmental impact. A potent carotenoid is astaxanthin in view of its health-promoting and antioxidative properties. It consists of different geometrical isomers with trans and cis configuration. In X. dendrorhous this carotenoid is mostly found in the trans form, but cis isomers can also be found. Carotenoid production was investigated in culture medium containing by-products such as raw glycerol (from biodiesel) and parboiled rice effluent. The effects of the culture medium components on biomass concentration and specific and volumetric productions of carotenoids were verified by the Plackett-Burman design. Cultivations were carried out with yeast Xanthophyllomonas dendrorhous NRRL Y-17268 at 25 °C and 150 rpm for 168 h. In this study, maximum production of carotenoids was obtained under the following conditions (in g/L): raw glycerol 10, glucose 10, yeast extract 10, malt extract 10 and peptone 1 at pH=6. Resulting specific and volumetric productions of carotenoids were 326.8 and 4.1 µg/g, respectively.