Evaluation of pectinolytic activities for oenological uses from psychrotrophic yeasts

Of the twenty-three morphotypes of yeasts isolated from soil capable of utilizing pectin as sole carbon source at 6 degrees C, two yeast isolates, one psychrotolerant (PT1) and one psychrophilic (SPY11), were selected according to their ability to secrete pectinolytic enzymes under some oenological conditions (temperature 6 and 12 degrees C and pH 3 . 5) and ability or inability to grow above 20 degrees C, respectively. As compared to their optimal activity, the three pectinolytic enzymes viz., pectin methyl esterase (PME), endopolygalacturonase (endo-PG) and exopolygalacturonase (exo-PG) isolated and assayed at pH 3 . 5 from PT1 were found to retain 39, 60 and 60% activity at 12 degrees C and 40, 79 and 74% activity at 28 degrees C, respectively. Likewise, the enzymes PME and endo-PG at pH 3.5 from SPY11 displayed 46 and 86% activity at 12 degrees C and 50 and 60% activity at 28 degrees C, respectively. All these enzymes showed 20-90% of residual activity at pH 3.5 and 6 degrees C. The yeast isolates PT1 and SPY11 were identified as Rhodotorula mucilaginosa and Cystofilobasidium capitatum, respectively, on the basis of morphological, physiological and molecular characteristics. This study presents the first report on pectinolytic activities under major oenological conditions from psychrotolerant isolate R. mucilaginosa PT1 and psychrophilic isolate C. capitatum SPY11.