AISLAMIENTO Y EVALUACI????N DE CEPAS TERMOTOLERANTES DE Saccharomyces cerevisiae PARA LA PRODUCCI????N DE AGUARDIENTES Y RONES ISOLATION AND EVALUATION OF THERMOTOLERANT STRAINS OF Saccharomyces cerevisiae FOR AGUARDIENTE AND RUM PRODUCTION

摘要

Resumen Thermotolerant strains of Saccharomyces cerevisiae were isolated from the residual yeast resulting from industrial fermentations subjected to thermal stress. The isolated strains were purified and characterised morphologically and biochemically. The thermal tolerance of one of the selected strains was evaluated in laboratory-scale batch fermentations at temperatures between 30 and 45???°C. The high ethanol yield (0.41 g g ?￠????1 ) at 40???°C demonstrated the thermotolerance of the selected strain. In six industrial-scale experimental runs the selected strain yielded a mean ethanol concentration of 5.2% (v/v), which was higher than the 4.8% (v/v) achieved with a reference industrial strain. Furthermore, a more complete substrate utilisation was achieved and the fermentation time was shortened from 16 to 12 h. The use of the thermotolerant strain resulted favorable for rum and aguardiente production since the formation of by-products, such as acetaldehyde, ethylacetate, methanol, n-propanol, isobuthanol and isoamyl alcohol was reduced. Se aislaron cepas termotolerantes de Saccharomyces cerevisiae a partir de levadura residual de fermentaciones industriales sometidas a estr????s t????rmico. Las cepas aisladas fueron purificadas y caracterizadas morfol???3gica y bioqu???-micamente. La tolerancia t????rmica de una cepa seleccionada fue evaluada en fermentaciones discontinuas a escala de laboratorio a temperaturas entre 30 y 45???°C. El alto rendimiento (0,41 g g ?￠????1 ) a 40???°C demostr???3 el car????cter termotolerante de la cepa seleccionada. La introducci???3n de la cepa en seis corridas experimentales a escala industrial permiti???3 aumentar la concentraci???3n promedio de etanol de 4,75 a 5,23% (v/v) en comparaci???3n con lo obtenido con una cepa industrial usada como referencia. Adem????s, se logr???3 un mayor agotamiento del sustrato y se acort???3 el tiempo de fermentaci???3n de 16 a 12 h. El uso de la cepa termotolerante permiti???3 reducir la concentraci???3n de subproductos como acetaldeh???-do, acetato de etilo, metanol, n-propanol, isobutanol y alcohol isoam???-lico en los aguardientes producidos. Palabras clave: Saccharomyces cerevisiae , tolerancia t????rmica, tolerancia a etanol, producci???3n de ron