Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2006
Publication Date: 1/2/2007
Citation: Prasongsuk, S., Berhow, M.A., Dunlap, C.A., Weisleder, D., Leathers, T.D., Eveleigh, D.E., Punnapayak, H. 2007. Pullulan production by tropical isolates of Aureobasidium pullulans. Journal of Industrial Microbiology and Biotechnology. 34(1):55-61.
Interpretive Summary: Improved methods are needed to produce high-value carbohydrate products from agricultural materials. Microbial germplasm from unique environments in Thailand were surveyed, and promising organisms were identified for production of the valuable polysaccharide, pullulan. This work will be of interest to researchers developing new uses and value-added products from agricultural commodities and byproducts.
Technical Abstract: Tropical isolates of Aureobasidium pullulans previously isolated from distinct habitats in Thailand were characterized for their capacities to produce the valuable polysaccharide, pullulan. A. pullulans strain NRM2, a so-called "color variant" strain, was the best producer, yielding 25.1 g pullulan/l after 7 days in sucrose medium with peptone as the nitrogen source. Pullulan from strain NRM2 was less pigmented than those from the other strains and was remarkably pure after a simple ethanol precipitation. The molecular weight of pullulan from all cultures dramatically decreased after 3 days growth, as analyzed by high performance size exclusion chromatography. Alpha-amylase with apparent activity against pullulan was expressed constitutively in sucrose-grown cultures and induced in starch-grown cultures. When the alpha-amylase inhibitor acarbose was added to the culture medium, pullulan of slightly higher molecular weight was obtained from late cultures, supporting the notion that alpha-amylase plays a role in the reduction of the molecular weight of pullulan during the production phase.