• Journal of Microbiology
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• v.45 no.6
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• pp.510-514
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• 2007

Twenty-five bacterial strains that secrete mucous materials were isolated from sediment obtained from King George Island, Antarctica. Seven of these strains proved capable of producing cryoprotective exopolysaccharides. The strain KOPRI 21653 was selected for the further study of an anti-ice-nucleating polysaccharide (ANP), which originated from a polar region. KOPRI 21653 was identified as Pseudoalteromonas arctica as the result of 16S rRNA analysis. The exopolysaccharide, P-21653, was purified completely from the KOPRI 21653 cell culture via column chromatography and protease treatment. The principal sugar components of P-21653 were determined to be galactose and glucose, at a ratio of 1:1.5, via GC-MS analysis. The cryoprotective activity of P-21653 was characterized via an E. coli viability test. In the presence of 0.1% (w/v) P-21653, the survival ratio of E. coli cells was as high as 82.6% over three repeated freeze-thaw cycles. The survival ratio decreased drastically to 71.5 and 48.1 %, respectively, in five and seven repeated cycle conditions; however, the survival ratios were greater over three (96.6-92.1%) to seven (100.5-91.6%) freeze-thaw cycles in the presence of 0.5 and 1.0% (w/v) P-21653. In addition, at much lower concentrations (0.1-1.0%), P-21653 resulted in survival ratios (83.1-98.4%) similar to those of two commercially available cryoprotectants ($V_{EG}$ plus X-1000, 92.9% and $V_{M3}$, 95.3%), which were utilized at the recommended concentrations (90%). The biochemical characteristics of exopolysaccharide P-21653 reflect that this compound may be developed as a useful cryoprotectant for use in medical applications and in the food industry.

• Korean Journal of Microbiology
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• v.54 no.1
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• pp.60-68
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• 2018

A cold-active and alkaline serine protease (Pro21717) was partially purified from the Antarctic marine bacterium Pseudoalteromonas arctica PAMC 21717. On a zymogram gel containing skim milk, Pro21717 produced two distinct clear-zones of approximately 37 kDa (low intensity) and 74 kDa (high intensity). These were found to have identical N-terminal sequences, suggesting they arose from an identical precursor and that the 37 kDa protease might homodimerize to the more active 74 kDa form of the protein. Pro21717 displayed proteolytic activity at $0-40^{\circ}C$ (optimal temperature of $40^{\circ}C$) and maintained this activity at pH 5.0-10.0 (optimal pH of 9.0). Notably, relative activities of 30% and 45% were observed at $0^{\circ}C$ and $10^{\circ}C$, respectively, in comparison to the 100% activity observed at $40^{\circ}C$, and this enzyme showed a broad substrate range against synthetic peptides with a preference for proline in the cleavage reaction. Pro21717 activity was enhanced by $Cu^{2+}$ and remained stable in the presence of detergent surfactants (linear alkylbenzene sulfonate and sodium dodecyl sulfate) and other chemical components ($Na_2SO_4$ and metal ions, such as $Ba^{2+}$, $Mg^{2+}$, $Ca^{2+}$, $Zn^{2+}$, $Fe^{2+}$, $K^+$, and $Na^{2+}$), which are often included in commercial detergent formulations. These data indicate that the psychrophilic Pro21717 has properties comparable to the well-characterized mesophilic subtilisin Carlsberg, which is commercially produced by Novozymes as the trademark Alcalase. Thus it has the potential to be used as a new additive enzyme in laundry detergents that must work well in cold tap water below $15^{\circ}C$.