Optimization of biotechnological parameters and characterization of catalytic properties of thermostable polygalacturonase from a chromium tolerant strain of Trichoderma pseudokoningii

Résumé

The hexavalent chromium tolerant strain of Trichoderma pseudokoningii, isolated from chromium enriched tannery effluent was found to produce extracellular polygalacturonase even in presence of chromium. Although there was a negative correlation between the amount of hexavalent chromium present in the cultivation medium and amount of polygalacturonase produced, moderate amount (300 U/ml) of enzymes was found to be produced even in presence of high amount of hexavalent chromium (0.80 gm/ml) in medium. The strain was found to synthesise maximum level of polygalacturonase when the culture medium was supplemented with 1.5 % (w/v) pure pectin as sole carbon source at pH 7.0 and 37oC. The highest level of extracellular enzyme synthesis could be achieved at 72nd hour of growth. The enzyme was stable under a wide range of pH (5.0-8.0) and up to 80 % of enzymatic activity was retained even after exposure to 90oC for 30 minutes.