| Popis: |
The purification and characterization of an extracellular lichenase from the fungus Penicillium occitanis Pol6 were studied. The strain produced the maximum level of extracellular lichenase (45 ± 5 U ml −1 ) when grown in a medium containing oat flour (2%, w/v) at 30 °C for 7 days. The purified enzyme EG L showed as a single protein band on SDS–PAGE with a molecular mass of 20 kDa. Its N-terminal sequence of 10 amino acid residues was determined as LDNGAPLLNV. The purified enzyme showed an optimum activity at pH 3.0 and 50–60 °C. The half-lives of EG L at 60 °C and 70 °C were 80 min and 21 min, respectively. Substrate specificity studies revealed that the enzyme is a true β-1,3-1,4- d -glucanase. The enzyme hydrolyzed lichenan to yield trisaccharide, and tetrasaccharide as the main products. Under simulated mashing conditions, addition of EG L (20 U/ml) or a commercial β-glucanase (20 U/ml) reduced the filtration time (25% and 21.3%, respectively) and viscosity (10% and 8.18%, respectively). These characteristics indicate that EG L is a good candidate in the malting and brewing industry. |
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