Kiyoshi Nara

Food Applications of Curdlan

Curdlan is a polysaccharide produced by bacteria and a homopolymer of glucose with β-1,3-glucosidic linkage. Its unique characteristic is its ability to form a firm, resilient and thermo-irreversible gel when heated in an aqueous suspension higher than 800C. Also, the curdlan gel does not melt even when it is heated to above 1000C, for example, during processes such as thermal sterilization. Moreover, curdlan gel, which is different from the gels made from other gelling agents, such as carrageenan, agar-agar and konjac, is stable against freezing and thawing.

Purification of human leukocyte interferon A derived from Escherichia coli: An aging process to prevent the formation of its oligomers

Abstract Recombinant human leukocyte interferon A (rIFN-αA) was purified from Escherichia coli cells by monoclonal antibody affinity chromatography (Ab) and CM-cellulose column chromatography (CM). By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the CM eluate was found to contain a large amount of rIFN-αA oligomers, in addition to the monomer, linked by intermolecular disulfide bonds. In contrast, the Ab eluate was found to contain a large amount of rIFN-αA monomers. These results show that the oligomers were formed at the CM step. Free SH groups were detected at a significant level in the Ab eluate, but were detected barely in the CM eluate, indicating that the Ab eluate contained some amount of the unstable monomer with free SH groups. To prevent the formation of the oligomers we established a simple and easily scaled-up process, called an aging process, during which the Ab eluate was incubated at pH 3.3 at 37°C for several days. This process is effective for changing the unstable monomer to the stable monomer and thus preventing the formation of the oligomers.