Volume 1 Issue 2

Microbial modification of starch with Ophiostoma spp . was investigated, with the purpose of developing a novel packaging material for the food or pharmaceutical industries. Various starch sources, such as tapioca, potato, corn, rice and amylopectin were tested as raw materials. The initial screening demonstrated that tapioca and potato starch had better performance for biopolymer production. The yield was about 85%. Preliminary characterization of the modified biopolymer was also conducted. Following microbial conversion, the percentage of molecules with at least a Mw of 10M Daltons increased from 25% to 89% after 3 days, confirming that the modification increased the weight of the starch polymer. Fourier Transform Infrared (FT-IR) revealed changes in the chemical structure of the starch after the modification. Both pure starches and the modified biopolymers were cast into films and tested for mechanical properties. The tensile tests showed that after treatment with the fungus, the peak stress and modulus of the films increased about 10 and 40 times, respectively. Also, the water barrier property was improved. Therefore, microbial modification positively impacted proper-ties relevant to the proposed application s . Although the role of the fungus in the modification and the function-property relationship of the biopolymer are not yet completely clear, the results of this study show promise for development of a novel biopolymer that competes with existing packaging materials.

Various hydrophilic polyelectrolytes, including cationic starch products, are used by papermakers to promote inter-fiber bonding and increase paper’s dry-strength. Thus, papermakers can meet customer require-ments with a lower net cost of materials, more recycled fibers, or higher mineral content. In the absence of polymeric additives, key mechanisms governing bond development between cellulosic fibers include capillary action, three-dimensional mixing of macromolecules on facing surfaces, conformability of the materials, and hydrogen bonding. Dry-strength additives need to adsorb efficiently onto fibers, have a hydrophilic character, and have a sufficiently high molecular mass. Though it is possible to achieve significant strength gains by optimal usage of individual polyelectrolytes, greater strength gains can be achieved by sequential addition of oppositely charged polyelectrolytes. Superior strength can be achieved by in-situ formation of polyelectrolyte com-plexes, followed by deposition of those complexes onto fiber surfaces. Polyampholytes also hold promise as efficient dry-strength additives. Opportunities for further increases in performance of dry-strength agents may involve fiber surface modification, self-assembled layers, and optimization of the dry film characteristics of dry-strength polymers or systems of polymers.