ENHANCED STABILITY OF BACILLUS LICHENIFORMIS L-ARABINOSE ISOMERASE BY IMMOBILIZATION WITH ALGINATE

Abstract

Recombinant Escherichia coli whole cells harboring Bacillus licheniformis L-arabinose isomerase (BLAI) were harvested to prepare alginate-immobilized biocatalysts. The operational conditions for immobilization were optimized according to relative activity and the cell leakage of the immobilized cell. The optimal conditions are as follows: alginate concentration, Ca²⁺ concentration, cell mass loading, and curing time were 2% (w/v), 0.1 M, 50 g l⁻¹, and 4 hours, respectively. After immobilization, cross-linking with 0.1% glutaraldehyde significantly reduced cell leakage. The immobilized whole cells harboring BLAI were very stable with 89% residual activity remaining after 33 days of incubation at 50°C and were much more stable than the free enzyme and cells. The results showed that immobilizing whole cells harboring BLAI is suitable for use as a biocatalyst in the production of L-ribulose, largely due to its high stability and low cost.

Keywords:

• alginate
• Bacillus licheniformis
• immobilization
• L-arabinose isomerase
• recombinant Escherichia coli
• stability

ACKNOWLEDGMENTS

This paper was supported by Konkuk University in 2009.