Preparation and properties of proteases immobilized on anion exchange resin with glutaraldehyde

The role of immobilized rennet on carbon cloth in flavor development during ripening of Gouda cheese

Rennet-free Gouda (RFG) cheese was prepared to investigate the influence of rennet on the non-volatile and volatile profiles of cheese and was characterized by HPLC and GC/MS analyses. Chymosin, a major protease in rennet, was immobilized onto oxidized and chemically modified carbon cloth. The chymosin immobilization efficiency was 60.4%, and the milk-clotting activity used as an index of the stability of the immobilized chymosin decreased by around 20% in 2 weeks. However, the activity was maintained at 70-80% from 2 weeks to 32 weeks and was more stable than that of chymosin solution alone. Non-volatile (organic acids) and volatile profiles of the RFG cheese and rennet-containing normal Gouda cheese were not significantly different during ripening with a few exceptions. Therefore, it can be concluded that cheese flavor is developed by lactic acid fermentation, irrespective of the presence of rennet.

The properties of immobilized caldolysin, a thermostable protease from an extreme thermophile

Caldolysin, the extracellular thermostable metal-chelator-sensitive lytic protease from Thermus T-351 was immobilized to Sepharose 4B, CM-cellulose, and controlled pore glass (CPG). Although protein binding efficiencies were high (96, 88, and 95%), some loss of enzyme activity occurred on immobilization (26, 69, and 89%). The pH optimum of both CM-cellulose and CPG-immobilized Caldolysin was decreased by about one pH unit. The K(m) for Sepharose-Caldolysin was unchanged with respect to the free protease, while those for CM-cellulose-Caldolysin and CPG-Caldolysin were lower by approximately one order of magnitude. Immobilization to both Sepharose and CM-cellulose increased the thermostability of Caldolysin at high temperatures, while CPG-Caldolysin was less thermostable than the free protease.

High-yield method for immobilization of enzymes

Two types of polyethylenimine-coated glass microbeads (13-44 micrometer) were synthesized and used for the immobilization of glucose oxidase from Aspergillus niger and catalase from A. niger and beef liver. The two types of beads were distinguishable by differences in their surface topography. Immobilizations were performed by adsorption followed by treatment with glutaraldehyde. The immobilized-enzyme activities per unit support of all of the enzymes tested were compared with and found to be superior to the immobilized activities attainable on aminopropyl-activated glass microbeads. When enzyme was present in less than saturating amounts, the coated beads were able to remove 100% of the glucose oxidase activity initially present in the immobilization solution, with 78-87% of that activity expressed on the support surface. Bound glucose oxidase was more stable to thermal inactivation than native enzyme.