REACTION-ENGINEERING ASPECTS OF ALPHA-1,4-D-GLUCAN PHOSPHORYLASE CATALYSIS - COMPARISON OF PLANT AND BACTERIAL ENZYMES FOR THE CONTINUOUS SYNTHESIS OF D-GLUCOSE-1-PHOSPHATE

Some important process properties of alpha-1,4-glucan phosphorylases i solated from the bacterium Corynebacterium callunae and potato tubers (Solanum tuberosum) were compared. Apart from minor differences in the ir stability and specificity (represented by the maximum degree of mal todextrin conversion) and a 10-fold higher affinity of the plant phosp horylase for maltodextrin (K-M of 1.3 g/L at 300 mM of orthophosphate) , the performances of both enzymes in a continuous ultrafiltration mem brane reactor were almost identical. Product synthesis was carried out over a time course of 300-400 h in the presence or absence of auxilia ry pullulanase (increasing the accessibility of the glucan substrate f or phosphorolytic attack up to 15-20%). The effect of varied dilution rate and reaction temperature on the resulting productivities was quan titated, and a maximum operational temperature of 40 degrees C was ide ntified.