Enzymatic lactose hydrolysis using two yeast and two fungal lactases that are of current technical interest was studied. The enzymes were compared regarding their oligosaccharide production. Parameters influencing oligosaccharide formation, together with the effect of immobilization were examined and conditions minimizing oligosaccharide content in the hydrolysis product were proposed. Enzymatic whey hydrolysis was also considered. A possibility of enzymatic lactose recombination from its hydrolysis products was shown.

Formation of oligosaccharides during enzymatic lactose hydrolysis and their importance in a whey hydrolysis process: Part II: Experimental.

The production of galacto-oligosaccharides (GOS) from lactose by Aspergillus oryzae beta-galactosidase immobilized on cotton cloth was studied. A novel method of enzyme immobilization involving PEI-enzyme aggregate formation and growth of aggregates on individual fibrils of cotton cloth leading to multilayer immobilization of the enzyme was developed. A large amount of enzyme was immobilized (250 mg/g support) with about 90-95% efficiency. A maximum GOS production of 25-26% (w/w) was achieved at near 50% lactose conversion from 400 g/L of lactose at pH 4.5 and 40 degrees C. Tri- and tetrasaccharides were the major types of GOS formed, accounting for about 70% and 25% of the total GOS produced in the reactions, respectively. Temperature and pH affected not only the reaction rate but also GOS yield to some extend. A reaction pH of 6.0 increased GOS yield by as much as 10% compared with that of pH 4.5 while decreased the reaction rate of immobilized enzyme. The cotton cloth as the support matrix for enzyme immobilization did not affect the GOS formation characteristics of the enzyme under the same reaction conditions, suggesting diffusion limitation was negligible in the packed bed reactor and the enzyme carrier. Increase in the thermal stability of PEI-immobilized enzyme was also observed. The half-life for the immobilized enzyme on cotton cloth was close to 1 year at 40 degrees C and 21 days at 50 degrees C. Stable, continuous operation in a plug-flow reactor was demonstrated for about 3 days without any apparent problem. A maximum GOS production of 26% (w/w) of total sugars was attained at 50% lactose conversion with a feed containing 400 g/L of lactose at pH 4.5 and 40 degrees C. The corresponding reactor productivity was 6 kg/L/h, which is several-hundred-fold higher than those previously reported.

Immobilization of β‐Galactosidase on Fibrous Matrix by Polyethyleneimine for Production of Galacto‐Oligosaccharides from Lactose

Analysis of diffusion models for protein adsorption to porous anion-exchange adsorbent.

Protein behavior at surfaces: orientation, conformational transitions and transport.

Biocatalytic membrane reactors have been widely used in different industries including food, fine chemicals, biological, biomedical, pharmaceuticals, environmental treatment and so on. This article gives an overview of the different immobilized enzymatic processes and their advantages over the conventional chemical catalysts. The application of a membrane bioreactor (MBR) reduces the energy consumption, and system size, in line with process intensification. The performances of MBR are considerably influenced by substrate concentration, immobilized matrix material, types of immobilization and the type of reactor. Advantages of a membrane associated bioreactor over a free-enzyme biochemical reaction, and a packed bed reactor are, large surface area of immobilization matrix, reuse of enzymes, better product recovery along with heterogeneous reactions, and continuous operation of the reactor. The present research work highlights immobilization techniques, reactor setup, enzyme stability under immobili...

Immobilized biocatalytic process development and potential application in membrane separation: a review

Enzyme adsorption from a finite bath (batch adsorption) onto porous spherical supports is investigated both experimentally and theoretically using β-galactosidase and Duolite ion-exchange resin as a model system. Efficient numerical techniques are presented that have been used in conjunction with a parameter estimation routine to evaluate adsorption isotherm constants. Results show that even for adsorption processes lasting almost 10 h, the majority of the enzyme is confined to the outer half of the support and, for high initial enzyme concentrations in the bath, this loading takes place as a slowly moving front. Information on the enzyme distribution has practical importance in the design of immobilized enzyme reactors that in previous works have almost always been analyzed assuming a uniform catalyst distribution.

Ernst Stuker

Papers

Enzyme adsorption in porous supports: local thermodynamic equilibrium model.