两水相系统萃取糖化酶的相平衡

含有聚乙二醇(PEG)和硫酸铵(NH_4)_2SO_4的两水相系统,能有效地用于从发酵液中提取糖化酶。研究表明:随着PEG平均分子量降低、成相组分浓度的适当增加以及加入较高浓度的无机盐,均能提高酶的分配系数。PEG浓度增大,(NH_4)_2SO_4浓度的减小有利于相比的增大。在同一条系线上,相比的确定应从提取收率和酶的浓缩两方面综合考虑。已发现,在含有26%PEG400-16%(NH_4)_2SO_4,pH4.4的系统中(相比1.2),糖化酶的分配系数为47,收率为96%。

Phase Equilibrium of Extraction of Glucoamylase in an Aqueous Two-Phase System

Liquid-liquid extraction offers a new method for extraction of biopolymers. Aqueous two-phase system containing polyethylene glycol(PEG) and ammonium sulfate (NH_4)_2SO_4 can be effectively used for the extraction of glucoamylase from fermentation broth. Important parameters for the partition of glucoamylase have been investigated, e. g., the average molecular weight of PEG, the concentration of the phase forming components, the addition of salt, the volume ratio of the top and bottom phase etc. Experimental results demonstrate that the partition coefficient of glucoamylase increases with reducing average molecular weight of PEG and increasing concentration of the phase-forming components, it increases also at higher concentration of salt added. Simultaneously, increasing the concentration of PEG and/or reducing the concentration of (NH_4)_2SO_4 result in increasing the volume ratio of phase systems. On the same tie line, the volume ratios of phase systems must be considered from both the yield and concentration of enzyme. It was found that in the system containing 26% PEG 400 and 16% (NH_4)_2SO_4 (volume ratio of 1.2) at pH=4.4, the partition coefficient of glucoamylase is 47 with 96% yield.