2.5 Pectinase Assay
The pectinase activity of the crude culture filtrate was assayed according to the modified method of
Miller (1959) as reported by Wang et al. (1997). The reaction mixture consisted of 0.80 ml of 1.0% w/v polygalacturonic acid in 100 mM Na2CO3−NaHCO3 buffer (pH 9.0) and 0.20 ml of supernatant (enzyme
solution). Control tubes (Enzyme blank) contained the same amount of substrate and 0.2 ml of the crude filtrate (enzyme solution) boiled for 10 min. Both the experimental and control tubes were incubated at 40 °C for 30 min. The reaction was terminated by the addition of 1.5 ml of 3,5-Dinitrosalicyclic acid (DNSA) reagent and the absorbance was taken at 540nm. One unit of pectinase activity was defined as the amount of enzyme that liberated reducing sugar equivalent to 1 μmol galacturonic acid per minute under the specified assay conditions (Karthik et al.,2011). A standard calibration curve of galacturonic acid was constructed and used for the estimation of
the polygalacturonic acid equivalent in μmol/ml/min.