the performance of an ultrafiltration hollow-fiber reactor, in which the enzymatic synthesis of glucose 6-phosphate from glucose and cofactor atp and the enzymatic regeneration of atp from adp and acetyl phosphate are performed simultaneously, was analyzed theoretically. a simple analytical model in which the liquid flowing in the fiber tubes is assumed to be plug flow, and the radial concentration gradients in the tube and shell sides are both neglected, could simulate the reactor performance with satisfactory accuracy. the simulation elucidated the effects of the reactor configurations and various operational conditions on glucose conversion, atp recycle number, and space-time yield. if the fiber tubes, through which the permeability of the relevant components such as substrates is high, were packed as much as possible in the reactor, good reactor performance could be expected. furthermore, with a sufficiently high enzyme concentration, low atp concentration in the feed solution, and appropriate space velocity, good space-time yield with high glucose conversion and with very high atp recycle number is theoretically possible. (author abstract) 60 refs