Water availability affects extracellular hydrolytic enzyme production by Aspergillus flavus and Aspergillus parasiticus

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dc.contributor.author Alam, Sahib -
dc.contributor.author Shah, Hamid Ullah -
dc.contributor.author Magan, Naresh -
dc.date.accessioned 2012-02-29T23:00:58Z
dc.date.available 2012-02-29T23:00:58Z
dc.date.issued 2009-08-31T00:00:00Z -
dc.identifier.citation Sahib Alama, Hamid Ullah Shaha and Naresh Magan. Water availability affects extracellular hydrolytic enzyme production by Aspergillus flavus and Aspergillus parasiticus. World Mycotoxin Journal, 2009, volume 2, number 3, pp313-322
dc.identifier.issn 1875-0710 -
dc.identifier.uri http://dx.doi.org/10.3920/WMJ2008.1108 -
dc.identifier.uri http://dspace.lib.cranfield.ac.uk/handle/1826/7036
dc.description.abstract The objectives of this study were to examine the effect of different water activities (a(w); 0.99, 0.96 and 0.94) and time (up to 120 h) on quantitative and specific enzyme production during germination and initial growth of Aspergillus flavus and A. parasiticus strains at 25 degrees C. This is an important early indicator of potential for aflatoxin production under conducive conditions. Qualitative API ZYM generic enzyme strips were used to identify key hydrolytic enzymes produced. Subsequently, the temporal effects of a(w) on the total/specific activity of the key 4-5 hydrolytic enzymes were determined using 4-nitrophenyl substrates in a 96-well microtitre plate assay. The main enzymes produced by germinating conidia of A. flavus were esterase, lipase, acid phosphatase, beta-glucosidase and N-acetyl-beta-D-glucosaminidase, while for A. parasiticus these were alkaline phosphatase, lipase, acid phosphatase and beta- fucosidase for both total (mu mol 4-nitrophenol/min/g) and specific activity (nmol beta-nitrophenol/min/mu g protein). There were significant increases in the specific activity of all these enzymes of germinating spores of A. flavus (0-120 h) except for beta-glucosidase which was maximum at 72 h. The total/ specific activities of the enzymes produced by A. flavus were maximum at 0.99 a (w) with the exception of acid phosphatase and N-acetyl-beta-D-glucosaminidase at 0.94 a(w) For A. parasiticus, maximum total activity occurred at 0.99 aw for fucosidase activity, while specific activity was found to be higher at lower a (w) levels. These enzymes are important in early colonisation of food matrices by these species and single factors (a(w) time) and two-way interactions were all statistically significant for the enzymes assayed for both species. These enzymes could be used as an early and rapid indicator of the activity of Aspergillus section flavi species and suggests that rapid infection may occur over a wide range of a(w) conditions. en_UK
dc.language.iso en_UK -
dc.publisher Wageningen Academic Publishers en_UK
dc.subject water activity aflatoxigenic fungi hydrolytic enzymes total activity specific activity Aspergillus section flavi fusarium proliferatum maize biosynthesis temperature moniliforme penicillium infection substrate kernels fungi en_UK
dc.title Water availability affects extracellular hydrolytic enzyme production by Aspergillus flavus and Aspergillus parasiticus en_UK
dc.type Article -


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