Abstract
The present research was mainly concerned with the immobilization of lipase（EC 3.1.1.3）from Pseudomonas fluorescens IFO 12055 on chitosan bead, for preparing S-AMPA（S-Acethylthio-2-Methylpropionic Acid） by enantioselective hydrolysis of racemic MAMP（Methyl-3-Acetylthio- 2-Methylpropionate）. We found that MAMP and AMPA could hydrolyze not only the ester-bonding but also the thioester-bounding. The Molecular Weight of the lipase estimated by Gel Filtration and SDS-PAGE was 68kDa. This enzyme was constituted of two subunits （about 36kDa）.The optimum temperature for free lipase and immobilized lipase on chitosan bead was 50℃, and optimum pH was 8.0. The Km（Michaelis constant）value of the immobilized enzyme was close to that of free enzyme. The Vmax value of the immobilized enzyme was lower than that of the free enzyme. Immobilized enzyme retains more than 80% of its activity for 30 batchs. It was confirmed that S-AMPA with 88%（e.e.）of optical purity was produced when reaction was done at 30℃ pH=7.6 by immobilized enzyme.