Modification of alternan by dextranase |
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Authors: | Timothy D Leathers Melinda S Nunnally Gregory L Côté |
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Institution: | (1) Bioproducts and Biocatalysis Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, IL 61604, USA |
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Abstract: | Alternan is a unique glucan with a backbone structure of alternating α-(1 → 6) and α-(1 → 3) linkages. Previously, we isolated
strains of Penicillium sp. that modify native, high molecular weight alternan in a novel bioconversion process to a lower molecular weight form
with solution viscosity properties similar to those of commercial gum arabic. The mechanism of this modification was unknown.
Here, we report that these Penicillium sp. strains secrete dextranase during germination on alternan. Furthermore, alternan is modified in vitro by commercial dextranases,
and dextranase-modified alternan appears to be identical to bioconversion-modified alternan. This is surprising, since alternan
has long been considered to be resistant to dextranase. Results suggest that native alternan may have localized regions of
consecutive α-(1 → 6) linkages that serve as substrates for dextranase. Dextranase treatment of native alternan, particularly
with GRAS enzymes, may have practical advantages for the production of modified alternan as a gum arabic substitute.
U.S. Department of Agriculture—Names are necessary to report factually on available data; however, the USDA neither guarantees
nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion
of others that may also be suitable. |
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Keywords: | Alternan Dextranase Gum arabic Modified alternan Viscosity |
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