Investigation on the immobilization of Pseudomonas isoamylase onto polysaccharide matrices

Abstract

This study examined Pseudomonas isoamylase immobilized onto polysaccharide matrices, among which included agarose, cellulose, and raw corn starch. For chemical binding of polysaccharides activated with tosyl chloride, a high specific activity of 23144 U/g-starch was obtained as compared with matrices of cellulose and agarose with 3229 U/g-cellulose and 84 U/g-agarose, respectively.

For raw corn starch, isoamylase desorption occurred when the immobilized enzyme by physical adsorption was subjected to 0.05 M acetate buffer with pH 5.2 at 40 °C; this is despite the considerable affinity between the enzyme and the matrix. In contrast, no detectable activity leached from the matrix for chemical binding, regardless of whether maltose, i.e. an affinity species to isoamylase, was added. For immobilized starch-isoamylase, its optimal activity performance was obtained in broader pH ranges of 3.5–5.5 and 5 °C higher than those of the free enzymes. More specifically, the free enzyme's activity markedly decreased within five hours while the immobilized starch-isoamylase exhibited a fairly stable behavior over a three day incubation period at 40 °C. After 175 days of storage at 4 °C, the residues of relative activity of 75% and 45% were obtained with respect to immobilized and free isoamylases, respectively.