Extracellular cellulase production by tropical isolates of Aureobasidium pullulans

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Abstract:

Cellulase production by Aureobasidium pullulans from the temperate regions has remained speculative, with most studies reporting no activity at all. In the current study, tropical isolates from diverse sources were screened for cellulase production. Isolates were grown on a synthetic medium containing cell walls of Msasa tree (Brachystegia sp.) as the sole carbon source, and their cellulolytic activities were measured using carboxymethyl cellulose and α-cellulose as substrates. All isolates studied produced carboxymethyl cellulase (endoglucanase) and alpha-cellulase (exoglucanase) activity. Endoglucanase-specific activities of ten selected isolates ranged from 2.375 to 12.884 µmol glucose·(mg protein)–1·h–1, while activities on α-cellulose (exoglucanase activity) ranged from 0.293 to 22.442 µmol glucose·(mg protein)–1·day–1. Carboxymethyl cellulose induced the highest cellulase activity in the selected isolates, while the isolates showed variable responses to nitrogen sources. The current study indicates that some isolates of A. pullulans of tropical origin produce significant extracellular cellulolytic activity and that crude cell walls may be good inducers of cellulolytic activity in A. pullulans.Key words: Aureobasidium pullulans, plant cell wall, cellulases, endoglucanase, exoglucanase.

La production de cellulase par Aureobasidium pullulans des régions tempérées demeure spéculative, la plupart des études ne rapportant aucune activité. Dans l'étude présente, des isolats tropicaux provenant de diverses sources ont été examinés pour leur production de cellulase. Les isolats furent cultivés dans un milieu synthétique contenant des parois cellulaires brutes de Brachystegia spiciformis en tant que seule source de carbone et leurs activités cellulolytiques furent mesurées en employant le carboxyméthylcellulose et le α-cellulose comme substrats. Tous les isolats étudiés ont produit des activités de carboxyméthylcellulase (endoglucanase) et d'alpha-cellulase (exoglucanase). Les activités endoglucanase spécifiques de dix isolats sélectionnés ont oscillé entre 2,375 et 12,884 µmol de glucose·(mg protéines)–1·h–1 alors que les activités sur l'α-cellulose (activité exoglucanase) ont oscillé entre 0,293 et 22,442 µmol de glucose·(mg protéines)–1·jour–1. La carboxyméthylcellulose a induit l'activité cellulase la plus élevée chez les isolats sélectionnés alors que les isolats ont démontré des réponses variables aux sources d'azote. L'étude présente indique que certains isolats de A. pullulans d'origine tropicale produisent une activité cellulolytique extracellulaire significative et que les parois cellulaires brutes pourraient être de bons inducteurs de l'activité cellulolytique de A. pullulans.Mots clés : Aureobasidium pullulans, parois cellulaires de plante, cellulases, endoglucanases, exoglucanases.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2005

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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