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KMID : 1007520130220051359
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Food Science and Biotechnology
2013 Volume.22 No. 5 p.1359 ~ p.1365
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Influence of Sodium Chloride on Thermal Denaturation of a High-Salt-Tolerant Neutral Protease from Aspergillus oryzae
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Wang Dong
Zheng Zhi-Yong
Feng Jie
Zhan Xiao-Bei
Zhang Li-Min
Wu Jian-Rong
Lin Chi-Chung
Zhu Li
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Abstract
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The temperature and pH stability of proteases have been extensively investigated. A neutral protease produced by Aspergillus oryzae was thermodynamically characterized at high-salt environment. When the protease was tested at 24% NaCl and 60oC, its half-life was increased to 30.0 min, 111% longer than that of control. Its Gibbs free energy and activation energy for denaturation in high NaCl concentration solutions were higher than in low salt solutions and increased by 2.1 and 4.75 kJ/mol, respectively. The protease exhibited higher thermal stability in higher salt conditions. This feature is beneficial to soybean sauce fermentation by enhancing the protease performance and taste of the product. Analysis by farultraviolet circular dichroism (far-UV CD) spectroscopy revealed that α-helix conformation in the protease increased from 3.2 to 31.7%, respectively, when the NaCl concentration increased from 0 to 18%, in agreement with the results deduced by thermodynamic calculations.
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KEYWORD
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Aspergillus oryzae, protease, thermal denaturation, ionic strength, kinetics
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