Pectinolytic yeast isolates for cold-active polygalacturonase production

Pectin rich cold stored spoiled fruits, vegetables and cold soils were screened and different pectinolytic isolates were obtained by enrichment culturing and ruthenium red plate assay. Among the primary isolates 10-15% were yeast isolates. Six isolates with higher zones of pectin hydrolysis were selected and tested for polygalacturonase (PGU) production at room temperature (25 degrees C) and at 5 degrees C. One isolate identified as Saccharomyces sp. with highest polygalacturonase activity at 5 degrees C was used for enzyme production using raw fruit pectins as substrates. The isolate was identified by preliminary cultural, morphological and sugar fermentation tests. PGU production was high in raw pectin substrates like orange peel (21 U/ml), apple peel (20 U/ml), mango peel (19 U/ml), grape must (18 U/ml) and guava peel (15 U/ml). Selected Saccharomyces sp. was found to grow at room temperature and produce good polygalacturonase active at 5 degrees C. Cold-active PGU could have ample application in fruit juice clarification as these conditions are milder and also prevent spoilage. The present study concentrated on enzyme production using the cheaper raw pectin rich substrates. Industrial relevance: The manuscript contains information on the cold active polygalacturonase produced by yeast at room temperature. It has industrial application for fruit juice clarification at cold (mild) conditions as it is a cold active enzyme. Also the enzyme is produced at room temperature by yeast considered as a GRAS organism. Therefore, it is a significant observation by the authors. (C) 2011 Elsevier Ltd. All rights reserved.