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A fluidized bed reactor was designed, constructed, and tested for handling microencapsulated urease. The working volume of the reactor was 10 mL, with a minimum fluidization velocity of 7.7 × 10−5 m/s. An even suspension of the microcapsules was obtained at fluid velocities between 1.5 × 10 4 and 6.0 × 10−4 m/s without breakage of the shear-sensitive microcapsules. The mixing behavior in the reactor was evaluated using pulse input tracer experiments and the hydrolysis rates of urea in continuous flow experiments were evaluated under various operating conditions.

An alternative approach to the regeneration of coenzymes is described here using immobilized microorganisms possessing “NADH-oxidase” function. Bacteria containing NADH-oxidase activity are immobilized by microencapsulation within artificial cells. In this form, the microencapsulated bacteria can recycle NADH back to NAD in the presence of molecular oxygen as an electron acceptor. The only byproduct of the recycling reaction is water. In order to perform the biological regeneration of NAD, the activity of NADH-oxidase was investigated in 13 strains of aerobic bacteria and yeast. The NADH-oxidizing bacteria Leuconostoc mesenteroides exhibited the highest activity among the microorganisms tested. The permeabilized bacteria showed 10% of their initial activity after microencapsulation. Light and electron microscopy studies of bacteria loaded microcapsules have been done. Enzymatic properties of microcapsule-immobilized bacteria were investigated in comparison with those of the free enzyme complex. Leuconostoc mesenteroides, containing NADH-oxidase, has been micro-encapsulated together with 3α-hydroxysteroid dehydrogenase (3α-HSDH) for stereospecific steroid oxidation.