Reaction Engineering Aspects of α-1,4-D-Glucan Phosphorylase Catalysis Comparison of Plant and Bacterial Enzymes for the Continuous Synthesis of D-Glucose-1 -Phosphate

摘要

Some important process properties of α-l,4-D-glucan phosphory-lases isolated from the bacterium Corynebacterium callunae and potato tubers (Solarium tuberosum) were compared. Apart from minor differences in their stability and specificity (represented by the maximum degree of maltodextrin conversion) and a 10-fold higher affinity of the plant phosphorylase for maltodextrin (K_M of 1.3 g/L at 300 mM of orthophosphate), the performances of both enzymes in a continuous ultrafiltration membrane reactor were almost identical. Product synthesis was carried out over a time course of 300-400 h in the presence or absence of auxiliary pullulanase (increasing the accessibility of the glucan substrate for phosphorolytic attack up to 15-20%). The effect of varied dilution rate and reaction temperature on the resulting productivities was quantitated, and a maximum operational temperature of 40°C was identified.