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United States Department of Agriculture

Agricultural Research Service

Research Project: PATHWAY ENGINEERING OF FUNGI FOR IMPROVED BIOPROCESS APPLICATIONS

Location: Renewable Product Technology Research Unit

Title: Modified Alternan: A Novel Microbial Gum with Potential as a Low-Viscosity Bulking Agent

Authors
item Leathers, Timothy
item Nunnally, Melinda
item Cote, Gregory

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 20, 2010
Publication Date: July 20, 2010
Citation: Leathers, T.D., Nunnally, M.S., Cote, G.L. 2010. Modified alternan: A novel microbial gum with potential as a low-viscosity bulking agent [abstract]. Institute of Food Technologists. Presentation 065-01.

Technical Abstract: Alternan is a microbial gum produced by rare strains of the GRAS lactic acid bacterium, Leuconostoc mesenteroides. The unique alternating alpha-(1,6) and alpha-(1,3) linkage pattern of this glucan imparts high solubility and resistance to most digestive enzymes. Previously, we invented a bioconversion method to modify alternan to lower molecular weight forms with rheological properties that resemble those of gum arabic or ultrasonicated alternan. Subsequently, we discovered that alternan could also be modified in vitro using commercial dextranase. This is surprising, since alternan has long been considered to be resistant to dextranase. In this report we optimize conditions for production of modified alternan using commercial dextranase from Chaetomium erraticum. This enzyme is considered GRAS and thus suitable for potential food applications. Optimal conditions were 10% alternan, pH 4.5, 50°C, and 125 IU dextranase/ml (assayed at 28°C, pH 5.0). Using these conditions, we scaled up production of modified alternan, permitting a more detailed structural analysis. Methylation analysis revealed a loss of linear 1,6 linkages during modification. Solutions of modified alternan are highly stable from 4 to 70 degrees C and pH 3-9. However, alternan solutions lack the emulsification capacity of gum arabic. Dry powders of modified alternan are bright white and not highly hygroscopic. Other forms of alternan are already being used in food products. Thus, modified alternan is promising for further development for food applications requiring a low-viscosity bulking agent. Optimized conditions will be useful to produce modified alternan for applications testing.

Last Modified: 7/25/2014
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