A tannase with a molecular mass of 72 kDa was obtained from Penicillium herquei isolated from valonia acorns following fermentation in a 5 L bioreactor. This tannase showed optimum activity at pH 6.0 and $30^{circ}C$. The enzyme was inhibited by $Fe^{3+}$, $Zn^{2+}$, dithiothrietol (DTT), ${eta}$-mercaptoethanol, formaldehyde, and ethanol, and induced by $K^+$, $Mn^{2+}$, Tween 80, and Triton X-100. The Michaelis constant ($K_m$) and the second-order constant ($k_{cat}/K_m$) values of the tannase for propyl gallate (PG) were 0.62 mM and 174.1 mM/sec. The circular dichroism (CD) spectra indicated that the secondary structure of the tannase contained 14% ${alpha}$ helix, 32.4% anti-parallel ${eta}$-sheet, 4.8% ${eta}$-sheet, 18.8% ${eta}$-turn, and 30% random coil. Native tannase in ultrapure water manifested as spherical nano-particle aggregates with diameters ranging from 50 to 300 nm determined by atomic force microscopy (AFM).