The Study On Immobilized β-Galactosidase And Its Application In Synthesis Of Galactooligosaccharides

β-galactosidase can synthesizes galactooligosacchrides (GOS) at high level of lactose. The immobilization of β -galactosidase was investigated in order to make full use of lactose from whey industrially. The good method of immobilization of β -galactosidase was studied, then the immobilized β-galactosidase was applied to synthesize GOS.Whey powder was reconstituted to the solution with determined concentration of lactose for the working samples. The yield of GOS was monitored with TLC corrected with HPLC.Aspergillus-oryza-β-galactosidase was adsorbed on chitosan and cross-linked with glutaraldehyde. The optimal parameters included: cross-linking followed with immobilization, under 4 C, immobilization for 6h, glutaraldehyde pH6.0, 1.0%; under the room temperature for 30min. The enzyme concentration was 0.4mg/g dry chitosan beads. The activity yield reached 26.43%, which was not ideal for enzymatic preparation of GOS.Consequently, calcium alginate gel was used to entrap β-galactosidase. The optimums as follows: 2.54% high-viscosity-sodium alginate, 0.88%gelatin, 0.24%low- viscosity-sodium alginate, 2.0%CaCl2, under which condition the gel got the best stability that can be used 8 times on end and the activity yield was 80%. Then immobilized enzyme entrapped in gel was characterized. The immobilized enzyme entrapped with alginate was showed that its optimal temperature rises 5 C to 55 C, optimal pH raised 0.5, endurance to temperature and pH were both better than soluble enzyme which showed that this kind of immobilized enzyme can be used directly and conveniently.The immobilized enzyme entrapped in alginate-gelatin gel was used to produce GOS from reconstituted whey. Through single factor experiments and SAS analysis, optimal conditions included lactose concentration, 37.4%; reaction time, 2.0h; temperature, 58.2 C; pH 5.0-6.0, enzyme concentration, 0.14%. The maximum GOS concentration was estimated as 28.9%, which was proved as 29.1 % in the trials with 1L reconstituted whey.Immobilized β-galactosidase can be made by entrapment in alginate and gelatin with high activity yield and good practical stability, having the industrial prospect to synthesize GOS.