“…Chitosan support might have a protecting effect at the high temperatures at which enzyme deactivation takes place. Immobilization of catalase in chitosan beads can cause an increase in the enzyme rigidity which is commonly re�ected by increase in stability towards denaturation by raising the temperature [45,46]. at 4 ○ C and the activity measurements were carried out for a period of 60 days (Figure 4).…”
Catalase was partially purified fromMalva sylvestrisL. and immobilized onto chitosan. Then, its catalytic properties were investigated. (NH4)2SO4precipitation and dialysis were performed in the extracted enzyme. Further purification was performed with sephadex G-200 column. Kinetic studies of the purified enzyme activity were measured and characterized. The inhibitory effects of KCN, NaN3, CuSO4, and EDTA onM. sylvestrisL. catalase activity were observed except NaCl. Furthermore,M. sylvestrisL. catalase was immobilized covalently with glutaraldehyde onto chitosan particles. The pH and temperature optima as well as the changes in the kinetics (Km, Vmax) of the immobilized and freeM. sylvestrisL. catalase were determined. The Km value for immobilized catalase (23.4 mM) was higher than that of free enzyme (17.6 mM). Optimum temperature was observed higher than that of the free enzyme. The optimum pH was the same for both free and immobilized catalases (pH 7.50). Immobilized catalase showed higher storage and thermal stabilities than free catalases. Free catalase lost all its activity within 60 days whereas immobilized catalase lost 45% of its activity during the same incubation period at 4°C. The remaining immobilized catalase activity was about 70% after 8 cycles of batch operations.
“…Chitosan support might have a protecting effect at the high temperatures at which enzyme deactivation takes place. Immobilization of catalase in chitosan beads can cause an increase in the enzyme rigidity which is commonly re�ected by increase in stability towards denaturation by raising the temperature [45,46]. at 4 ○ C and the activity measurements were carried out for a period of 60 days (Figure 4).…”
Catalase was partially purified fromMalva sylvestrisL. and immobilized onto chitosan. Then, its catalytic properties were investigated. (NH4)2SO4precipitation and dialysis were performed in the extracted enzyme. Further purification was performed with sephadex G-200 column. Kinetic studies of the purified enzyme activity were measured and characterized. The inhibitory effects of KCN, NaN3, CuSO4, and EDTA onM. sylvestrisL. catalase activity were observed except NaCl. Furthermore,M. sylvestrisL. catalase was immobilized covalently with glutaraldehyde onto chitosan particles. The pH and temperature optima as well as the changes in the kinetics (Km, Vmax) of the immobilized and freeM. sylvestrisL. catalase were determined. The Km value for immobilized catalase (23.4 mM) was higher than that of free enzyme (17.6 mM). Optimum temperature was observed higher than that of the free enzyme. The optimum pH was the same for both free and immobilized catalases (pH 7.50). Immobilized catalase showed higher storage and thermal stabilities than free catalases. Free catalase lost all its activity within 60 days whereas immobilized catalase lost 45% of its activity during the same incubation period at 4°C. The remaining immobilized catalase activity was about 70% after 8 cycles of batch operations.
“…A similar shift in optimum temperature has been observed for enzymes entrapped in gel matrices and the phenomenon has been attributed mainly to enzyme stabilization due to restricted enzyme movement. [33][34][35].…”
Section: Effect Of Ph On Enzyme Activitymentioning
Immobilization of Lecitase (Phospholipase A1) in gelatin hydrogel and its stability is studied with a view to utilizing the immobilized enzyme for degumming rice bran oil. Excellent retention of enzyme activity ([80%) is observed in hydrogel containing 43.5% gelatin crosslinked with glutaraldehyde. Compared to the free enzyme which has a broad pH-activity profile (6.5-8.0), the activity of the immobilized enzyme is strongly dependent on pH and has a pH-optimum of pH 7.5. The optimum temperature of enzyme activity increases from 37 to 50°C. Compared to the free enzyme which loses all its activity in 72 h at 50°C, the immobilized enzyme retains its activity in full. The immobilized enzyme has been used efficiently in a spinning basket bioreactor for the degumming of rice bran oil with 6 recycles without loss of enzyme activity. The phosphorus content of the oil decreases from 400 ppm to 50-70 ppm in each cycle. After charcoal treatment and dewaxing, a second enzymatic treatment brings down the phosphorus content to \5 ppm.
“…The conformational flexibility of the enzyme was affected by immobilization. Immobilization of laccase on chitosan beads caused an increase in the enzyme rigidity which was commonly reflected by increase in stability towards denaturation by raising the temperature (Jiang and Zhang 1993; Mohamed and Naby 1993). Fig.…”
Objectives(S)-Mandelate dehydrogenase (SMDH) and laccase were immobilized on chitosan. The bi-enzymatic system with immobilized SMDH and immobilized laccase was taken to catalyze the stereoselective transformation of racemic mandelic acid and (R)-mandelic acid was obtained from its racemic mixture.ResultsCharacteristics of the immobilized enzymes were valuated. The optimum pH and temperature of the immobilized SMDH were found to be pH 3.4 and 45 °C, and these of the immobilized laccase were about pH 6.0 and 55 °C, respectively. The K
m value of the immobilized SMDH for racemic mandelic acid was 0.27 mM and that of the immobilized laccase for ferrocyanide was 0.99 mM. The thermal and storage stabilities of these enzymes were improved with immobilization. The enantiomeric purity of the bi-enzymatically produced (R)-mandelic acid was determined to be over 99%.ConclusionThe immobilized bi-enzymatic system for the stereoselective transformation of racemic mandelic acid showed higher productivity, faster reaction velocity, and more stable catalytic ability.Graphical abstract.
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