Continuous d‐Tagatose Production by Immobilized Thermostable l‐Arabinose Isomerase in a Packed‐Bed Bioreactor

Abstract d ‐Tagatose was continuously produced using thermostable l ‐arabinose isomerase immobilized in alginate with d ‐galactose solution in a packed‐bed bioreactor. Bead size, L/D (length/diameter) of reactor, dilution rate, total loaded enzyme amount, and substrate concentration were found to be optimal at 0.8 mm, 520/7 mm, 0.375 h ‐ 1 , 5.65 units, and 300 g/L, respectively. Under these conditions, the bioreactor produced about 145 g/L tagatose with an average productivity of 54 g tagatose/L·h and an average conversion yield of 48% (w/w). Operational stability of the immobilized enzyme was demonstrated, with a tagatose production half‐life of 24 days.