Purification and characterization of a thermostable pullulanase from Thermoactinomyces thalpophilus

摘要: Thermoactinomyces thalpophilus No. 15 produced an extracellular pullulanase in aerobic fermentation with soluble starch, salts, and complex nitrogen sources. Acetone fractionation, ion-exchange chromatography, gel filtration purified the enzyme from cell-free broth 16-fold to electrophoretically homogeneous state (specific activity, 1352 U/mg protein; yield, 4%). The (estimated MW 79 000) was optimally active at pH 7.0 70°C retained 90% relative activity 80°C (30 min) absence of substrate. activated by Co2+, inhibited Hg2+, exhibited enhanced stability presence Ca2+. hydrolyzed pullulan (K m 0.32%, w/v) forming maltotriose, amylopectin 0.36%, w/v), beta-limit dextrin 0.45%, glycogen 1.11%, maltotriose maltose.