RESUMEN
The aim of this work was to obtain insights about the factors that determine the lactose fermentative metabolism of Kluyveromyces marxianus UFV-3. K. marxianus UFV-3 and Kluyveromyces lactis JA6 were cultured in a minimal medium containing different lactose concentrations (ranging from 0.25 to 64 mmol l(-1)) under aerobic and hypoxic conditions to evaluate their growth kinetics, gene expression and enzymatic activity. The increase in lactose concentration and the decrease in oxygen level favoured ethanol yield for both yeasts but in K. marxianus UFV-3 the effect was more pronounced. Under hypoxic conditions, the activities of ß-galactosidase and pyruvate decarboxylase from K. marxianus UFV-3 were significantly higher than those in K. lactis JA6. The expression of the LAC4 (ß-galactosidase), RAG6 (pyruvate decarboxylase), GAL7 (galactose-1-phosphate uridylyltransferase) and GAL10 (epimerase) genes in K. marxianus UFV-3 was higher under hypoxic conditions than under aerobic conditions. The high expression of genes of the Leloir pathway, LAC4 and RAG6, associated with the high activity of ß-galactosidase and pyruvate decarboxylase contribute to the high fermentative flux in K. marxianus UFV-3. These data on the fermentative metabolism of K. marxianus UFV-3 will be useful for optimising the conversion of cheese whey lactose to ethanol.
Asunto(s)
Proteínas Fúngicas/metabolismo , Microbiología Industrial/métodos , Kluyveromyces/metabolismo , Lactosa/metabolismo , Micología/métodos , Aerobiosis , Anaerobiosis , Biomasa , Medios de Cultivo , Productos Lácteos , Inducción Enzimática , Etanol/metabolismo , Fermentación , Proteínas Fúngicas/genética , Regulación Fúngica de la Expresión Génica , Kluyveromyces/enzimología , Kluyveromyces/genética , Kluyveromyces/crecimiento & desarrollo , Piruvato Descarboxilasa/genética , Piruvato Descarboxilasa/metabolismo , ARN de Hongos/genética , Reacción en Cadena en Tiempo Real de la Polimerasa , Especificidad de la Especie , UDPglucosa 4-Epimerasa/genética , UDPglucosa 4-Epimerasa/metabolismo , UDP-Glucosa-Hexosa-1-Fosfato Uridiltransferasa/genética , UDP-Glucosa-Hexosa-1-Fosfato Uridiltransferasa/metabolismo , beta-Galactosidasa/genética , beta-Galactosidasa/metabolismoRESUMEN
OBJECTIVES: To study the incidence of galactosaemia in the state of São Paulo and the benefit/cost (B/C) ratio of the introduction of neonatal screening for galactosaemia, comparing it with a selective approach. METHODS: An enzymatic-colorimetric assay was used for the screening of total galactose (TG) in a sample of 10% of the births in São Paulo in one year and positive cases were confirmed by the activity of galactose-1-phosphate uridyltransferase (GALT). Detected and referred cases were genotyped using enzyme restriction studies for Q188R, N314D and S135L mutations of the GALT gene. The economic analysis was determined by calculating the B/C ratio and by analysis of sensitivity as a function of the incidence of the disease detected and the variation of the interest rate in the economy. RESULTS: 59 953 newborns were screened for TG, with 3 cases of galactosaemia being identified (0.26% false positives), corresponding to a frequency of 1:19 984 liveborns (95% confidence interval: 1:7494 to 1:59 953). One classical case and one Duarte 2 variant referred to as a selective approach were confirmed. With an incidence of 1:19 984, the B/C ratio was 1.04 for the 11.75% interest rate in effect in Brazil, with values already decapitalized. With a maximum possible incidence of 1:7494, the B/C ratio was 2.79. DISCUSSION: There is an economic advantage in introducing neonatal screening for galactosaemia in the national neonatal screening programme. This advantage could increase with a reduction of the current interest rates in the economy.