Efecto de diámetro de esfera y densidad celular en la producción de etanol con levadura inmovilizada en alginato / Effect of pellet diameter and cell density on ethanol production with alginate immobilized yeast

Las células inmovilizadas tienen aplicación potencial en la producción de biocombustibles posibilitando la reutilización de biomasa, el empleo de diversas configuraciones de reactores y sistemas de cultivo, el manejo de altas densidades celulares alcanzando altas productividades volumétricas, y la simplificación de operaciones de procesamiento de salida. El objetivo del presente estudio fue evaluar la influencia del diámetro de las perlas y la densidad celular en la producción de etanol con Saccharomyces uvarum inmovilizada en alginato al 2% (p/v). Para ello se evaluaron tres diámetros de perlas de 2, 2,5 y 3 mm. Las células inmovilizadas fueron cultivadas en medio con 12% (p/v) de glucosa en biorreactores de columna sin agitación a 28 ºC, y se operaron cuatro lotes consecutivos de 48 horas cada uno. En cada lote se cuantificó el consumo de glucosa y se determinó la cantidad de etanol producido. Los rendimientos máximos de etanol para las esferas de 2, 2,5 y 3 mm de diámetro fueron 81, 83 y 97% del rendimiento teórico. La máxima productividad volumétrica de etanol fue 1,2 g/L-1/h-1 con un consumo de glucosa de 99,8% al término del lote, correspondiente a las columnas con perlas de 3 mm y con una producción de 0,017 g de etanol por esfera. La producción de etanol acumulada en cada sistema fue 178, 189 y 200 g/L-1 para 2, 2,5 y 3 mm respectivamente, encontrándose una relación directa con el diámetro de perla e inversa respecto a la densidad celular. Los rendimientos de etanol obtenidos son superiores a los reportados para la misma especie.

Immobilized cells have a potential use in biofuel production. They also allow re-using biomass, using diverse reactor configurations and culture systems, handling high cell densities to obtain high volumetric productivities and to simplify the downstream processing. The purpose of this work was to evaluate the influence of bead diameter and cell density on ethanol production using immobilized Saccharomyces uvarum in 2% (w/v) alginate. For that, three bead diameters (2, 2.5 and 3 mm) were evaluated. Immobilized cells were cultured on a 12% (w/v) glucose medium in column bioreactors without agitation at 28 °C for four 48 h–repeated batches. For each batch, both glucose consumption and ethanol produced were measured. Maximum yields for 2, 2.5 and 3 mm bead diameters were 81, 83 and 97% of theoretical yield. Maximum volumetric productivity of ethanol was 1.2 g/L-1/h-1 with 99.8% glucose consumption at the end of the batch, corresponding to the 3 mm bead diameter and the ethanol production per bead was 0.017 g. Accumulated ethanol production for each system was 178, 189 and 200 g/L-1 for 2, 2.5 y 3 mm bead diameter, respectively, being this directly related to bead diameter and inversely related to cell density. Ethanol yields were higher than those reported for the same species.

Effect of the trehalose levels on the screening of yeast as probiotic by in vivo and in vitro assays

Probiotics are viable defined microorganisms (bacteria or yeasts) that exert a beneficial effect on the health of the host when ingested in adequate amounts. Screening for such biotherapeutic agents is commonly performed by in vitro assays simulating gastrointestinal environment to determine the ability to survive in the digestive tract. In the present study, the possibility of extrapolation of data obtained in in vitro assays to in vivo conditions was studied using five Saccharomyces cerevisiae strains isolated from Brazilian Atlantic rain forest. Trehalose contents and survival after exposure to a combination of physiological stresses generally found in the gastrointestinal tract of humans were determined for the five yeasts and compared to the behavior of Saccharomyces boulardii, a well-known probiotic. The results were completed with the colonization capacity of the gastrointestinal tract of gnotobiotic mice by these yeast strains. Some results obtained by in vitro assays are not confirmed by in vivo experiments, indicating that the extrapolation cannot be always done.

Probióticos são definidos como microrganismos (bactérias e leveduras) que exercem um efeito benéfico na saúde do hospedeiro quando ingeridos em quantidades adequadas. A seleção desses agentes bioterapêuticos normalmente é feita por testes in vitro simulando o ambiente gastrointestinal que determina a capacidade de sobrevivência no trato digestivo. Neste trabalho, a possibilidade de extrapolação dos dados obtidos nos testes in vitro para as condições in vivo foi estudada utilizando cinco linhagens de Saccharomyces cerevisiae isoladas da floresta Atlântica brasileira. O conteúdo de trealose e a sobrevivência após a exposição a diversos estresses fisiológicos geralmente encontrados no trato gastrointestinal de humanos foram determinados para as cinco linhagens e os resultados comparados com a Saccharomyces boulardii, um probiótico conhecido. Esses resultados foram completados com a capacidade de colonização do trato gastrointestinal de camundongos gnotobióticos pelas leveduras. Pelos resultados obtidos, concluimos que os testes in vitro não são confirmados pelos ensaios in vivo, indicando que essa extrapolação não pode sempre ser feita.

Effect of sub culturing and lyophilization on viability and antagonistic activity of saccharomyces boulardii against some pathogenic bacteria

The effect of frequent subculturing, freezing and lyophilization in presence of cryoprotectives on antagonistic activity and viability of saccharomyces boulardii was studied. Results indicated that early subculturings led to increasing the antagonistic activity but this activity fell down gradually and diminished after 10 -11 of subculturing which indicated the cytoplasmic responsibility i.e., could be coded by plasmids or virus-like particles. Freezing at -20°C had no effect on the viability in the presence of cryoprotectives like skim milk powder, Mg-stearate or without them, since the cultures recovered at 99-99.2% after [4] days. Lyophilization had very overt effect on viability .Skim milk provided the best protection [8% reduction] followed by using distilled water and Mg-stearate .Saline had the greatest effect and caused [15% reduction]. Storage results of lyophilized samples at room temperature and refrigerator showed that skim milk was the best at both temperatures followed by distilled water, saline and then Mg-stearate which showed the highest reduction in viable count of yeast

Molecular analysis for rapid extraction of genomic DNA from medically important yeasts

Current methods of DNA extraction from four different pathogenic yeasts are often time-consuming and require the use of toxic and carcinogenic chemicals. DNA isolation from yeast organisms is difficult due to cell walls or capsules that are not readily susceptible to lysis. We therefore investigated a new and rapid DNA isolation method using high-speed cell disruption [HSCD] incorporating chaotropic reagents and lysing matrices in comparison to standard phenol-chloroform [PC] extraction protocols for isolation of DNA from four medically important yeats [Saccharomyces cerevisiae, Candida utilis, Cryptococcus neoformans and Trichosporon beigelii]. Two different inocula [10[7] and 10[8] CFU] were compared for optimization of obtained yields. The entire extraction procedure was performed on as four samples within one hour compared to six hours for PC extraction. In comparison to the PC procedure, HSCD DNA extraction demonstrated significantly greater yields for 108 CFU of C. utilis, T. beigelii [P

Levaduras aisladas de mostos de uva en la zona de Oltrepo Pavese, Italia, y su sensibilidad in vitro frente a compuestos de cobre y zinc / Yeast isolated from musts of grapes in Oltrepó Pavese, Italy, and their in vitro sensibility to zinc and copper compounds

Se investigó durante el periodo 1989-90 en la región de Oltrepó Pavese (Italia), la micota de los mostos provenientes de uvas negras y blancas. De un total de 28 especies levaduriformes aisladas, incluidas en 10 géneros, Saccharomyces, fué el género dominante con las especies S.italicus y S.cerevisiae. Tambien se detectaron frecuentemente levaduras anascosporógenas, tales como Candida valida, Torulopsis (C) holmii y Kloeckera apiculata. Se efectuaron estudios de sensibiliadad in vitro frente a compuestos de CuSO4, ya sea en cepas de S. cerevisiae aisladas de los mostos, como de Alternaria, Botrytis, Cladosporium y Sporobolomyces, aisladas del filoplano de la uva. Las concentraciones de CuSO4 a 0.007M y a 0,062M, fueron fúngicidas para S.cerevisiae y Sporobolomyces roseus respectivamente