Background: Tannases are enzymes that may be used in different industrial sectors as, for example,
food and pharmaceutical. They are obtained mainly from microorganisms, as filamentous fungi.
However, the diversity of fungi stays poorly explored for tannase production. In this article,
Aspergillus ochraceus
is presented as a new source of tannase with interesting features for biotechnological
applications.
Results: Extracellular tannase production was induced when the fungus was cultured in
Khanna medium with tannic acid as carbon source. The extracellular tannase was purified 9-fold with
2% recovery and a single band corresponding to 85 kDa was observed in SDS-PAGE. The native
apparent molecular mass was estimated as 112 kDa. Optima of temperature and pH were 40ºC and
5.0, respectively. The enzyme was fully stable from 40ºC to 60ºC during 1 hr. The activity was
enhanced by Mn
2+ (33-39%) and NH
4
+ (15%). The purified tannase hydrolyzed tannic acid and methyl
gallate with Km of 0.76 mM and 0.72 mM, respectively, and Vmax of 0.92 U/mg protein and 0.68 U/mg
protein, respectively. The analysis of a partial sequence of the tannase encoding gene showed an
open read frame of 567 bp and a sequence of 199 amino acids were predicted. TLC analysis revealed
the presence of gallic acid as a tannic acid hydrolysis product.
Conclusion:The extracellular tannase
produced by
A. ochraceus showed distinctive characteristics such as monomeric structure and
activation by Mn
2+, suggesting a new kind of fungal tannases with biotechnological potential. Further, it
was the first time that a partial gene sequence for
A. ochraceus tannase was described.
