Immobilization of maltase from Saccharomyces cerevisiae on thiosulfonate supports

In this study, two commercial supports (Eupergit? C and Purolite? A109) were chemically modified in order to introduce thiosulfonate groups, which could subsequently exclusively react with cysteine residues on enzyme surface. Thereafter, the immobilization of maltase from Saccharomyces cerevisiae onto obtained thiosulfonate-activated supports was performed, resulting in high expressed enzymatic activities (around 50%), while on the other hand, immobilization on unmodified supports yielded expressed activities less than 5%. Moreover, protein loadings up to 12.3 mg g-1 and immobilized activities up to 3580 IU g-1 were achieved by employment of theses thiosulfonate supports. Desorption experiments, performed on samples taken during immobilization, proved that immobilization on thiosulfonate supports encompass first step of fast adsorption on support and second slower step of the covalent bond formation between thiosulfonate groups and thiol groups of cysteine. More importantly, although enzyme coupling occurs via covalent bond formation, performed immobilization proved to be reversible, since it was shown that 95% of immobilized activity can be detached from support after treatment with thiol reagent (?-mercaptoethanol), thus support can be reused after enzyme inactivation.

Improved Stabilities of Lipase by Immobilization on Eupergit C

Lipase is frequently used for catalyze wide non-natural substrates in order to obtain enantio- and regioselectivie substrates. This study evaluates the stabilities of lipase by immobilization on Eupergit C. The immobilized lipase had improved stability at 60oC for 60 h compared to the free lipase 1 h at 60oC. Immobilization resulted in an increase in pH stability over a range of 7.0 - 9.0 and about 54 days for half-life of storage at 4oC. The tolerance of lipase to organic solvents was also improved by immobilization, and the immobilized lipase showed activating activity when exposed to hydrophobic solvents.