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Antifreeze activities of poly(gamma-glutamic acid) produced by Bacillus licheniformis
Ing-Lung Shih1, Yi-Tsong Van, Yi-Yuan Sau
1Department of Environmental Engineering, Da-Yeh University, Chang-Hwa, Taiwan. ils@mail.dyu.edu.tw
Abstract:
Various enantiomeric isomers, metals salts and molecular sizes of poly(gamma-glutamic acid), gamma-PGA, produced by Bacillus licheniformis CCRC 12826, were prepared and their antifreeze activities were studied by differential scanning calorimetry. The antifreeze activity of gamma-PGA increased as its molecular weight decreased but was indifferent to its D/L-glutamate composition. The antifreeze activity was cation dependent decreasing in the order Mg2+ >> Ca2+ approximately Na+ >> K+ which follows that of inorganic chlorides in that high ionic charge leads to high antifreeze activity. The mechanism by which the cryoprotective effects of gamma-PGA can be explained is still yet to be determined.
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