RESUMO
Significant differences on structure, stability, and catalytic properties of tannase were found when this enzyme was produced under solid-state and submerged fermentations (SSF and SmF) by Aspergillus niger. The specific activity was 5.5 times higher on SSF than in SmF. Significant differences in isoelectric points of tannases were found. The pH optima for both types of enzyme was found at 6 and the pH stability of SSF and SmF tannase were at 6 and 5-8, respectively. The optimal temperature range was from 50 to 60 °C for SmF tannase and 60 °C for SSF tannase, and both enzyme types showed tolerance to high temperatures (60-70 °C). The SSF tannase showed a major specificity for methyl gallate substrate while SmF tannase for tannic acid. All metal ions tested, had an activity inhibition from 30-46% on SSF tannase. SDS-PAGE analysis as well as gel localization studies of both SSF and SmF purified tannases showed a single band with a molecular weight of 102 and 105 kDa, respectively. Different levels of glycosylation were found among SSF and SmF purified tannases. This is the first report about structural differences among tannase produced under SSF and SmF and this study provides basis for explanation of the stability and catalytic differences observed previously for this two tannase types.
