No abstract

Glycoside hydrolases (GH) are enzymes capable to hydrolyze the glycosidic bond between two carbohydrates or even between a carbohydrate and a non-carbohydrate moiety. Because of the increasing interest for industrial applications of these enzymes, the immobilization of GH has become an important development in order to improve its activity, stability, as well as the possibility of its reuse in batch reactions and in continuous processes. In this review, we focus on the broad aspects of immobilization of enzymes from the specific GH families. A brief introduction on methods of enzyme immobilization is presented, discussing some advantages and drawbacks of this technology. We then review the state of the art of enzyme immobilization of families GH1, GH13, and GH70, with special attention on the enzymes β-glucosidase, α-amylase, cyclodextrin glycosyltransferase, and dextransucrase. In each case, the immobilization protocols are evaluated considering their positive and negative aspects. Finally, the perspectives on new immobilization methods are briefly presented.

No abstract

No abstract

This paper aims to investigate the effects of some salts (NaCl, (NH4)2SO4 and Na2SO4) at pH 5.0, 7.0 and 9.0 on the stability of 13 different immobilized enzymes: five lipases, three proteases, two glycosidases, and one laccase, penicillin G acylase and catalase. The enzymes were immobilized to prevent their aggregation. Lipases were immobilized via interfacial activation on octyl agarose or on glutaraldehyde-amino agarose beads, proteases on glyoxyl agarose or glutaraldehyde-amino agarose beads. The use of high concentrations of salts usually has some effects on enzyme stability, but the intensity and nature of these effects depends on the inactivation pH, nature and concentration of the salt, enzyme and immobilization protocol. The same salt can be a stabilizing or a destabilizing agent for a specific enzyme depending on its concentration, inactivation pH and immobilization protocol. Using lipases, (NH4)2SO4 generally permits the highest stabilities (although this is not a universal rule), but using the other enzymes this salt is in many instances a destabilizing agent. At pH 9.0, it is more likely to find a salt destabilizing effect than at pH 7.0. Results confirm the difficulty of foreseeing the effect of high concentrations of salts in a specific immobilized enzyme.

β‐Glucosidases from two different commercial preparations, Pectinex Ultra SP‐L and Celluclast® 1.5L, were immobilized on divinylsulfone (DVS) supports at pH 5.0, 7.0, 9.0, and 10. In addition, the biocatalysts were also immobilized in agarose beads activated by glyoxyl, and epoxide as reagent groups. The best immobilization results were observed using higher pH values on DVS‐agarose, and for Celluclast® 1.5L, good results were also obtained using the glyoxil‐agarose immobilization. The biocatalyst obtained using Pectinex Ultra SP‐L showed the highest thermal stability, at 65°C, and an operational stability of 67% of activity after 10 reuses cycles when immobilized on DVS‐agarose immobilized at pH 10 and blocked with ethylenediamine. The β‐glucosidase from Celluclast® 1.5L produced best results when immobilized on DVS‐agarose immobilized at pH 9 and blocked with glycine, reaching 7.76‐fold higher thermal stability compared to its free form and maintaining 76% of its activity after 10 successive cycles. The new biocatalysts obtained by these protocols showed reduction of glucose inhibition of enzymes, demonstrating the influence of immobilization protocols, pH, and blocking agent.

No abstract

Properties of beta-glucosidase produced by Aspergillus niger URM 6642 recently isolated from the Atlantic rainforest biome and its potential tolerance to saccharification of lignocellulosic biomass products and fermentation inhibitors was evaluated. The fungus was cultivated under solid state culture conditions at 37°C with different agro-industrial wastes. High levels of beta-glucosidase (3778.9 U g