A novel strain, Bacillus fusiformis CGMCC1347, was utilized successfully to transform isoeugenol to vanillin and the product inhibition could be well avoided by using immobilized cells in the isoeugenol/aqueous biphasic system. The Bacillus fusiformis CGMCC1347 cells were entrapped into sodium alginate under conditions of 2.5% sodium alginate, 10% cells and 0.1 mol l-1 CaCl2. The optimum pH for free cells and immobilized cells were 4.0 and 3.5, respectively, and the optimum reaction temperature for both free and immobilized cells was 37 °C. The pH stabilities of free cells and immobilized cells were good at all investigated pH levels. For thermal stability, free cells were stable at 50°C60°C and the immobilized cells were stable at 50°C 80°C. The half-life of the immobilized cells was more than 25 d, comparing with less than 14 d for the free cells at 4°C.

Bacillus fusiformis CGMCC1347, screened from soil, was immobilized successfully to biotransform isoeugenol to vanillin. The optimal immobilization conditions were 2.5% sodium alginate, 10% cell density and Ca2+ 0.1 mol l-1. The optimal reaction conditions in a 2 L CSTR reactor with immobilized Bacillus fusiformis CGMCC1347 cells were isoeugenol 600 mL, immobilized cells 400 g, pH 3.5 dH2O 400 mL, 37 oC, 200 r min-1 shaking speed and 0.8 vvm air capacity. The average vanillin concentration reached 39.26 g l-1 after 6 times reuse of immobilized cells in 2 L CSTR.