Magnetic Fe3O4/Alginate Cell Beads: Application in Enzymatic Synthesis of Pharmaceutical Intermediate

The magnetic Fe3O4/Alginate cell beads (FACB) were prepared by entrapping cells of E. coli BL21(DE3) pET21a-NIT (a recombinant nitrilase producing strain) and nano-Fe3O4 with alginate. The FACB can be applied as an immobilized biocatalyst for the hydrolysis of 1-cyanocyclohexane acetonitrile to 1-cyanocyclohexane acetic acid, which is an important intermediate in the synthesis of Gabapentin. The optimal immobilization conditions were investigated in detail, including 3.0% (w/v) sodium alginate and 50 g/L Fe3O4. The mechanical strength of FACB was improved significantly compared with the alginate cell beads without Fe3O4. Compared with free cell, FACB have better pH stability and thermo-stability. Moreover, FACB showed excellent operation stability could be reused for 35 batches (420 h) and still remained 90% of its original activity.