Purification and characterization of an exochitinase from Bacillus thuringiensis subsp. aizawai and its action against phytopathogenic fungi

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Abstract:

A chitinolytic enzyme from Bacillus thuringiensis subsp. aizawai has been purified and its molecular mass was estimated ca. 66 kDa by sodium dodecyl sulfate – polyacryamide gel electrophoresis (SDS–PAGE). The enzyme was able to hydrolyze chitin to chitobiosides but not carboxymethylcellulose, cellulose, pullulan, and laminarin. Optimal pH and temperature were detected at 6 and 50 °C, respectively. Stability, in the absence of substrate, was observed at temperatures less than 60 °C and pH between 5 and 8. Enzyme activity was significantly inhibited by K+ and EDTA and completely inhibited by Hg2+. Purified chitinase showed lytic activity against cell walls from six phytopathogenic fungi and inhibited the mycelial growth of both Fusarium sp. and Sclerotium rolfsii. The biocontrol efficacy of the enzyme was tested in the protection of bean seeds infested with six phytopathogenic fungi.Key words: chitinase, Bacillus thuringiensis, purification, phytopathogenic fungi.

Une enzyme chitinolytique de Bacillus thuringiensis spp. aizawai as a été purifiée et sa masse moléculaire fut estimée à 66 kDa par électrophorèse sur gel de polyacrylamide avec dodécylsulfate de sodium (SDS–PAGE). L'enzyme fut capable d'hydrolyser la chitine en chitobiosides mais non le carboxyméthylcellulose, la cellulose, le pullulane et la laminarine. Le pH et la température optimaux étaient respectivement de 6 et 50 °C. La stabilité en absence de substrat fut observée à des températures inférieures à 60 °C et des valeurs de pH entre 5 et 8. L'activité enzymatique fut significativement inhibée par le K+ et l'EDTA et complètement inhibée par le Hg2+. La chitinase purifiée a démontré une activité lytique contre les parois cellulaires de six champignons phytopathogènes et a inhibé la croissance des mycéliums de Fusarium sp. et de Sclerotium rolfsii. L'efficacité de biocontrôle de l'enzyme fut mise à l'épreuve dans le contexte de la protection de graines de haricots infestés avec six champignons phytopathogènes.Mots clés : chitinase, Bacillus thuringiensis, purification, champignons phytopathogènes.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: July 1, 2006

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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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