Cell wall invertase immobilization within calcium alginate beads
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Yeast cell wall invertase (CWI) was immobilized within calcium alginate beads. The result of entrapment was the complete immobilization of all the added CWI. Three types of biocatalysts were prepared: CWI-S, CWI-155 and CWI-157. The optimum pH values were 4.5 and 5.0 for free and immobilized invertase, respectively. The optimum temperature was 60 °C, for both free CWI and CWI-S immobilizate. 80 °C was the optimum temperature for CWI-155 whereas the optimum temperature for CWI-157 ranged from 50 °C to 80 °C. Immobilized CWI was more stable than was free CWI above optimum activity temperatures. The activation energies were 32 kJ/mol for free CWI and 45, 21 and 25 kJ/mol for CWI-S, CWI-155 and CWI-157, respectively. The Km values of free and immobilized CWI-157 were 28.4 mM and 72 mM, respectively. The Vmax values were estimated as 4.5 mM/min and 0.42 mM/min, respectively. Immobilized CWI-157 was tested in a batch reactor using 70% sucrose (w/v). Complete sucrose conversion was achieved a...fter 55 h. After 40 consecutive cycles, CWI-157 retained 90% of its activity.
Keywords:Alginate / Cell wall invertase / Immobilization / Saccharomyces cerevisiae
Source:Food Chemistry, 2007, 104, 1, 81-86
- Elsevier Sci Ltd, Oxford