STATISTICAL OPTIMISATION OF CELL GROWTH AND CAROTENOID PRODUCTION BY RHODOTORULA MUCILAGINOSA

Sequential statistical methods were used to maximise carotenoid production by a strain of Rhodotorula mucilaginosa, isolated from the Brazilian ecosystem. Initially, a factorial 2(5-1) experimental design was used, and the variables were pH and the levels of glucose, yeast extract, MgSO4 center dot 7H(2)O and KH2PO4. The nitrogen source (yeast extract) was the most important variable in enhancing carotenoid production; MgSO(4 center dot)7H(2)O and KH2PO4 had a negative influence. The initial pH had no significant effect on carotenoid and cell productions. We further investigated the effects of glucose and yeast extract effects, using a second-order central composite design (CCD) to optimise carotenoid production, which was adequately approximated with a full quadratic equation obtained from a two-factor-2-level design. The analysis of quadratic surfaces showed that after 5 days of cultivation at 25 degrees C, the maximum carotenoid concentration (745 mu g l(-1)) was obtained with 15 g l(-1) of yeast extract and 20 g l(-1) of glucose. The maximum carotenoid production (152 mu g g(-1)) was obtained with 5 g l(-1) yeast extract and 10 g l(-1) glucose. Carotenoid formation was more sensitive to changes in yeast extract concentration than to changes in glucose concentration. Maximum cell production was achieved with 15-17 g l(-1) of yeast extract and 15-20 g l(-1) of glucose.43110911

Carotenoids of yeasts isolated from the Brazilian ecosystem

The carotenoid composition of pigmented yeasts isolated in Brazil was studied. The yeasts were cultured in yeast malt broth at 200 rpm, 25 degrees C, for 5 days, without illumination. Open column, thin layer and high performance liquid chromatography were used to separate, identify and quantify the carotenoids. The major pigments found in these yeasts were torulene and beta-carotene. beta-Carotene predominated in Rhodotorula graminis-125, Rhodotorula glutinis and Sporobolomyces roseus, while torulene was the principal carotenoid in Rhodotorula mucilaginosa. The yeast R. glutinis had the highest total carotenoid production (881 mu g/1), followed by R. graminis (594 mu g/1), Rhodotorula mucilaginosa-137 (590 mu g/1), Rhodotorula mucilaginosa-108 (562 mu g/1) and Rhodotorula mucilaginosa-135 (545 mu g/1). Rhodotorula minuta and S. roseus had the lowest carotenoid contents (168 and 237 mu g/1, respectively). In mu g/g of dry cells, R. glutinis had a total carotenoid concentration of 132 mu g/g. (C) 2007 Elsevier Ltd. All rights reserved.107114515