Control of Molecular Weight Distribution of the Biopolymer Pullulan Produced by the Fungus Aureobasidium Pullulans
Final rept. 1986-1987
ARMY NATICK RESEARCH AND DEVELOPMENT CENTER MA
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This report summarizes one section of this study, the evaluation of environmental conditions and their influence on the biopolymer pullulan molecular weight distribution and yield. Films, fibers, and chemical derivatives made from these different molecular weight products, and the characterization of these materials will provide the bases for another report. In order to determine optimum growth conditions for the control of molecular weight distribution of extracellular pullulan, preliminary studies utilized cell suspensions of nine strains of Aureo basidium pullulans. One strain, NRRL-Y 6220 A. pullulans, was selected for further study. Carbon and nitrogen sources, along with phosphate concentration were evaluated for their effect on pullulan yield and molecular weight distribution. Batch systems, scale-up batch, and including solvents, extraction time, etc., were also studied. Pullulan biopolymer products with weight average molecular weights from 100 thousand to 4 million, with a dispersity of around two, were produced. The evaluation of chemicalphysical properties of defined molecular weight fractions of pullulan is now under investigation. Keywords Fungus Nutrients Polysaccharides.