Production, purification, and characterization of a novel serine-esterase from Aspergillus westerdijkiae

Esterases hydrolyze water soluble short chain fatty acids esters and are biotechnologically important. A strain of Aspergillus westerdijkiae isolated from cooking oil for recycling was found to secrete an esterase. The best enzyme production (19-24 U/ml of filtrate) culture conditions were stablished. The protein was purified using ammonium sulphate precipitation, dialysis, and a chromatographic step in Sephacryl S-200 HR. The 32 kDa purified protein presented an optimal temperature of 40°C, with a T₅₀ of 48.95°C, and an optimal pH of 8.0. K_M and V_max were 638.11 µM for p-NPB and 5.47 µmol of released p-NP · min^-1  · µg^-1 of protein, respectively. The purified enzyme was partially active in the presence of 25% acetone. PMSF inhibited the enzyme, indicating that it is a serine hydrolase. MS enzyme peptides sequences were used to find the protein in the A. westerdijkiae sequenced genome. A structure model demonstrated that the protein is a member of the a/ß -hydrolase fold superfamily.