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, MgSO4.7H2O and KH2PO4. The nitrogen source (yeast extract) was the most important variable in enhancing carotenoid production; MgSO4.7H2O 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 25ºC, the maximum carotenoid concentration (745 µg l-1) was obtained with 15 g l-1 of yeast extract and 20 g l-1 of glucose. The maximum carotenoid production (152 µg 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.

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, MgSO4.7H2O and KH2PO4. The nitrogen source (yeast extract) was the most important variable in enhancing carotenoid production; MgSO4.7H2O 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 °C, the maximum carotenoid concentration (745 µg l(-1)) was obtained with 15 g l(-1) of yeast extract and 20 g l(-1) of glucose. The maximum carotenoid production (152 µg 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.

Selection and characterization of carotenoid-producing yeasts from Campinas region, Brazil

The objective of the present study was to select and identify yeasts from Brazil capable of producing carotenoids. Pigmented yeasts were isolated from soil, leaves, fruits, flowers and a processed product. The samples were incubated at 30°C in Erlenmeyer flasks, containing YM broth. After 48 hours, they were inoculated in Petri dishes with YM agar, and incubated at 30°C during 120 hours. The yeast colonies, which presented yellow to red coloration, were transferred to culture tubes containing YM agar, and incubated at 30°C for 72 hours. Out of 242 samples, only five had yellow to red color at high intensity. These highly pigmented yeasts were re-isolated in Petri dishes with YM agar and then transferred to tubes with GPYM agar. Identification through morphological and reproduction characteristics, along with physiological and biochemical tests, classified four strains as R. mucilaginosa and one strain as R. graminis. The main carotenoids extracted from them were identified through HPLC analysis as beta-carotene and torulene. The strains showed potential as promising microorganisms for the commercial production of carotenoids.

Este trabalho teve como objetivo selecionar e identificar leveduras encontradas no Brasil capazes de produzir carotenóides. As leveduras pigmentadas foram isoladas de amostras de solos, folhas, frutos, flores e um alimento processado. As amostras foram colocadas em frascos de erlenmeyer, contendo meio de Extrato de Malte e Levedura (YM), e incubadas a 30°C. Após 48 horas, as amostras foram inoculadas em placas de petri contendo meio YM ágar e incubadas a 30°C por 120 horas. As colônias, que apresentaram coloração entre amarelo e vermelho, foram transferidas para os tubos de culturas, contendo meio YM ágar e incubadas a 30°C por 72 horas. Das 242 amostras, somente cinco delas apresentaram coloração intensa entre amarelo e vermelho. Estas colônias de leveduras foram reisoladas, em placas de petri contendo YM ágar e, posteriormente, transferidas para tubos de ensaios contendo GPYM ágar. A identificação das leveduras, baseada nas características morfológicas, de reprodução, além dos testes fisiológicos e bioquímicos, classificou quatro linhagens como Rhodotorula mucilaginosa e uma como Rhodotorula graminis. Os principais pigmentos extraídos destas linhagens foram identificados através da análise de cromatografia de alta eficiência como beta-caroteno e toruleno. As linhagens de leveduras mostraram potencial como microrganismos promissores para a produção comercial de carotenóides por fermentação.

Influência da adiçäo de polifosfato e de gordura em sistemas carne-água-goma xantana / Effect to addition of polyphosphates and fat to the system meat-water-xanthan gum

Foi estudado o efeito da adiçäo de polifosfatos no sistema formado por carne-água-goma xantana e foi observado que esse sistema é täo estável ao cozimento quanto o sistema formado por carne-água-polifosfato. Entretanto o sistema formado pela mistura xantana-polifosfato (0,5 por cento de cada) foi superior ao sistema só com a goma xantana ou só com polifosfato (0,5 por cento ), pois as quantidades de caldo liberado foram 0,30 ml quando se usou polifosfato na concentraçäo de 0,5 por cento e 0,34 ml quando se utilizou goma xantana na concentraçäo de 0,5 por cento , enquanto que o sistema carne-água-polifosfato (0,5 por cento )-goma xantana (0,5 por cento ) 0,20 ml de caldo. Foi estudado também o efeito da adiçäo de gordura. A gordura foi adicionada nas concentraçöes de 0,6; 12,5; 25,0 e 30,0 por cento nos sistemas formados por carne-água, carne-água-goma xantana (1,0 por cento ), carne-água-goma xantana (0,5 por cento ), carne-água-polifosfato (0,5 por cento ) e carne-água-goma xantana (0,5 por cento )-polifosfato (0,5 por cento ). Foi observado que a adiçäo de gordura diminuiu a sinerese em todos os sistemas estudados. Dos sistemas testados, o formato por carne-água-goma xantana (0,5 por cento )-polifosfato (0,5 por cento ) foi o que mostrou a menor sinerese