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- 저자 : Hana Maalej (검색결과 2 건)
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Hana Maalej,Noomen Hmidet,Olfa Ghorbel-Bellaaj,Moncef Nasri 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.5
This study reports the purification and biochemical characterization of a novel maltotetraose-forming-α-amylase from Pseudomonas stutzeri AS22, designated PSA. The P. stutzeri α-amylase (PSA) was purified from the culture supernatant to homogeneity by Sepharose mono Q anion exchange chromatography, ultrafiltration and Sephadex G-100 gel filtration, with a 37.32-fold increase in specific activity, and 31% recovery. PSA showed a molecular weight of approximately 57 kDa by SDS-PAGE. The N-terminal amino acid sequence of the first 7 amino acids was DQAGKSP. This enzyme exhibited maximum activity at pH 8.0 and 55oC, performed stably over a broad range of pH 5.0 ~ 12.0, but rapidly lost activity above 50oC. Both potato starch and Ca2+ ions have a protective effect on the thermal stability of PSA. The enzyme activity was inhibited by Hg2+, Mn2+, Cd2+, Cu2+, and Co2+, and enhanced by Ba2+. PSA belonged to the EDTA-sensitive α-amylase. The purified enzyme showed high stability towards surfactants (Tween 20, Tween 80 and Triton X-100), and oxidizing agents, such as sodium per borate and H2O2. In addition, PSA showed excellent compatibility with a wide range of commercial solid and liquid detergents at 30oC, suggesting potential application in the detergent industry. Maltotetraose was the specific end product obtained after hydrolysis of starch by the enzyme for an extended period of time, and was not further degraded.
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Noomen Hmidet,Hana Maalej,Hanen Ben Ayed,Sofiane Ghorbel,Habib Kriaa,Moncef Nasri 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.4
Extracellular α-amylases produced by a newly isolated feather degrading bacterium strain Bacillus mojavensis A21 was optimized and characterized. Zymography showed that the A21 strain produced at least two α-amylases. Higher α-amylase production was achieved in the presence of 10 g/L chicken feathers and 1 g/L yeast extract. The growth of B. mojavensis A21 using chicken feathers as the nitrogen and carbon source resulted in its complete degradation after 48 h incubation at 37°C. However,maximum α-amylase activity was attained after 24 h. The optimum temperature and pH for crude α-amylase activity were 60°C and 6.5, respectively, and its activity was inhibited by EDTA. The end products of starch hydrolysis were maltose, maltotriose, and maltotetraose. α-Amylases from the A21 strain also catalyzed transglycosylation reactions when maltotetraose and maltopentaose were used as substrates and formed higher molecular weight maltoligosaccharides from G5 to G8. The maltooligosaccharide forming endo-α-amylases is useful in bread making as an anti-staling agent and can be produced economically using a low-cost medium with chicken feathers as the substrate.
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