Comparison of the salt-induced activation of Pseudomonas cepacia lipase in organic media by phosphate buffer and sodium sulfate

Abstract

The effects of a kosmotropic phosphate buffer (PB) or sodium sulfate (SS) on the enzymatic activity of crude Pseudomonas cepacia lipase (PCL) in organic media were explored. Previously, it was believed that SS acts as an effective enzyme activator, and PB was only used to adjust the solution pH. The present work showed PB-induced activation of PCL in the transesterification activity, where an increase of nearly 10-fold was achieved by carefully controlling the lyophilization condition. This activation, which gave about one-half of the native catalytic efficiency of PCL in aqueous media, was even more effective than the SS-induced activation. Thermogravimetric analysis of PCL preparations showed that different local environments surrounded PCL due to the presence of PB or SS. The local polarity of PCL preparations suspended in n -hexane was investigated by fluorescence spectroscopy using 2-(4'-amino-2'-hydroxy phenyl)benzoxazole as the probe. SS-incorporated PCL showed a much stronger local polarity than PB-incorporated and salt-free PCL. A correlation was found between the transesterification activity and local polarity of the enzyme preparation as a function of salt content. The data confirmed that the salt-induced activation of PCL in organic media can be attributed in part to the polar environment constituted by the salt-bonded water surrounding the PCL. 系统研究了Al掺杂TS-1 (Al-TS-1)分子筛的合成及其催化氧化性能, 采用X射线衍射/紫外-可见光谱/电感耦合等离子体发射光谱/扫描电镜/ 27 Al和 29 Si固体核磁共振等手段对Al-TS-1样品进行了表征. 结果表明, 在合成过程中, Al的引入会影响TS-1中骨架Ti的形成, 但当Al含量低于一定值(Al/Si ≤ 0.005)时, 其影响很小. Al-TS-1中骨架Al和骨架Ti均不对其相应的酸催化和催化氧化作用产生影响. 骨架Al抑制了Al-TS-1在碱性应用体系中的与Ti相邻Si的溶脱, 从而保护了骨架Ti活性中心. The catalytic activity of Pseudomonas cepacia lipase (PCL) in organic media was drastically enhanced by the addition of a kosmotropic phosphate buffer or sodium sulfate. This activation is probably due to the polar environment formed by the salt-bound water surrounding the PCL.