Dongbo Liu

Purification and Characterization of Extracellular Poly(β-hydroxybutyrate) Depolymerase from Penicillium sp. DS9701-D2

An extracellular poly (β-hydroxybutyrate) (PHB) depolymerase was purified from Penicillium sp. DS9701-D2. The molecular weight of the enzyme was estimated to be about 46.8 KDa by sodium dodecyl sulfate—polyacrylamide gel electrophoresis. The isoelectric point of 7.6 for the enzyme was determined by capillary electrophoresis. The optimum enzyme activity was detected at 30°C and pH 5.0. It was found that Na+ and K+ enhance the enzyme activity, whereas Zn2+, Mg2+, Cu2+, and Fe2+ inhibit it. The secondary structure of the enzyme was measured by circular dichroism (CD) spectroscopy. The main degradation product of depolymerase was indentified as 3-hydroxybutyrate dimer by mass spectrometer (MS) analysis.

Purification and properties of carboxymethylcellulase (CMCase) from a cellulose-decomposing bacterium Sporocytophaga sp JL-01

Sporocytophaga sp., a Gram-negative aerobic cellulose decomposing bacterium, is capable of gliding on the surface of solid medium. A new endoglucanase, carboxymethylcellulase (CMCase1), was purified from an aerobic bacterium Sporocytophaga sp. JL-01. The molecular weight of the enzyme was 82 kDa as determined by SDS Polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH was 5.0 and optimum temperature was 50 degrees C under experiment conditions. The Km of CMCase1 was 9 mgmL(-1) and Vmax was 27.3 ug min(-1)mg(-1) protein. The Zn2+ could inhibit the activity of this enzyme at ion concentration of 5 mM. RP-HPLC revealed that aromatic amino acid, acidic amino acid, and basic amino acid accounted for 10.5, 24.5 and 7.0%, respectively. The far-UV circular dichroism (CD) spectrum showed that the amount of beta-sheet was decreased with the temperature changed from 25 to 75 degrees C.