Chemical disruption of yeast cells for the isolation of carotenoid pigments

The red yeast Rhodotorula glutinis produces valuable carotenoid pigments which are used as natural food colorants and as a pigment source in fish diets. In this work R. glutinis was cultivated and harvested for carotenoid extraction after 3 days of fermentation. Five different solvents were used to disrupt the cell wall of freeze-dried R. glutinis cells and thus release the intracellularly produced carotenoids. Chromatographic analysis showed that three carotenoid pigments (P-carotene, torulene, and torularhodin) were present in the extract. A Box-Behnken experimental design was employed to investigate statistically the main and interactive effects of three of the five solvents tested (dimethyl sulfoxide, petroleum ether, and acetone) and saturated NaCl solution on the extent of extraction. An empirical model relating extraction yield to the four variables was developed on the basis of the experimental results. The model was shown to be a statistically significant description of the carotenoid extraction process and could be successfully used to derive the most efficient combination of the four variables to extract carotenoids from R. glutinis. Extraction conducted under the optimum conditions resulted in a high yield of carotenoids, suggesting that the combined chemical cocktail was effective at compromising the integrity of the R. glutinis cell wall. (c) 2006 Elsevier B.V. All rights reserved.