Detection of tannase activity
Tannase activity was detected by a visual reading method (Osawa
and Walsh, 1993) using a modified method of Chowdhury et al.
(2004). Fresh cultures on YMA containing 10 g/l tannin were harvested
and suspended in 750 μl substrate medium containing 33 mM NaH2PO4
and 20 mM methyl gallate for the purposes of preparing a dense suspension.
The substrate medium was incubated aerobically at 30 °C for
24 h. The mixture was later alkalinized by adding an equal amount of
a saturated NaHCO3 solution (pH 8.6) and then incubating it at 25 °C
for 1 h. This suspension was centrifuged to remove any cells and the
absorbance of the supernatant was measured at 440 nm. The supernatant
changed colour from green into brown. An absorbance value of
higher than 0.5, was considered a positive indication of tannase activity