Bacillus subtilis NRC33a levansucrase was immobilised on different carriers using different immobilisation methods including physical adsorption, covalent binding, ionic binding and entrapment. The immobilised enzyme prepared by covalent binding on chitosan through 3% gluteraldehyde had the highest immobilization yield (81.51%). Therefore, it was used as a typical example for Bacillus subtilis ...

The fundamentals of catalyst deactivation are presented in this review. The chemico-physical aspects concerning the various deactivation causes (i.e. poisoning, sintering, coking, solid-state transformation, masking, etc.) have been analyzed and discussed, along with the mathematical description of the deactivation phenomena. # 1999 Elsevier Science B.V. All rights

Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key...

Glutamine synthetase has been purified to homogeneity from two N,-fixing cyanobacteria, Anabaena cylindrica and a species of Nostoc (the phycobiont of Peltigera canina). The activities of the A . cylindrica enzyme in the biosynthetic and transferase assays were, respectively, 9-4 and 32 pmol product formed min-l (mg protein)-l; the corresponding values for the Nostoc sp. enzyme were 6.5 and 20....

Plants were engineered to confer resistance to thiazopyr, a member of the pyridine herbicide family, via an esterase deactivation mechanism. Earlier studies showed that transformation of thiazopyr to its monoacid metabolite resulted in loss of herbicidal activity (P.C.C. Feng et al., 1995, Xenobiotica 35, 27). Based on thiazopyr hydrolytic activity, a 60-kDa esterase was purified from rabbit li...

hydrogen can be produced for fuel cell applications by using methanol steam reforming reaction. in this article, a method was developed for regeneration of accelerated deactivated methanol-steam-reforming catalyst. successive deactivation–regeneration cycles were studied in a 250 hours test for the first time including 6 regeneration cycles. it is shown that regeneration of the catalyst in dilu...