Purification, Characterization and Thermodynamic Assessment of an Alkaline Protease by Geotrichum Candidum of Dairy Origin

Alkaline proteases is the important group of enzymes having numerous industrial applications including dairy food formulations. The current study deals with the purification and characterization of an alkaline serine protease produced by Geotrichum candidum QAUGC01, isolated from indigenous fermented milk product, Dahi. In total twelve G. candidum strains were screened for their proteolytic activity by using standard protease assay. The protease production from G. candidum QAUGC01 was optimized by varying physio-chemical conditions. The protease was purified by using two-step ammonium sulfate precipitation and gel filtration chromatography. Protease was further characterized by studying various parameter like temperature, pH, modulators, metal ions and organic solvent. A thermodynamic study was also carried out to explore the half-life of protease. The G. candidum grew profusely at 25 °C and at an initial pH of 4.0 for 72 h of incubation producing 26.21 U/mlmaximum extracellular protease. Protease revealed that Vmax and Km was 26.25 U.ml-1.min-1 and 0.05 mg.mL-1, respectively using casein as substrate. The enzyme was stable at a temperature range (25-45 ºC) and pH (8-9). Residual enzyme activity was strongly inhibited in the presence of PMSF (7.5%). The protease could hydrolyze proteinaceous substrates, casein (98%) and BSA (95%). The thermodynamic studies explored that the half-life of the enzyme that was 106.62 min, 38.72 min and 15.71 min at 50, 60 and 70 ºC, respectively. Purified protease from G. candidum GCQAU01 is an ideal candidate for industrial application.