Milk clotting and storage-tolerant peptidase from Aureobasidium leucospermi LB86

Peptidases are widely used for softening meat, hydrolyzing protein, baking, cheese, and making wine. A search for novel peptidases supports biotechnological innovation in the field of food chemistry. In general, microbial enzymes prospecting has mostly focused on filamentous fungi, and the potential of yeasts as enzyme producers has been little explored. This study focuses on a serine peptidase isolated from Aureobasidium leucospermi LB86. The purified enzyme was able to clot milk and, in storage assays, it maintained 90% of its activity for 40 days at 4 degrees C, and around 66% activity for 210 days. It had an estimated molecular mass of 33 kDa, highest activity at pH 7.0 and 45 degrees C, was stable in the pH range 5.5-9.0 at 4 degrees C and 25 degrees C, exhibiting activity higher than 75%, and retained 90% of activity at temperatures up to 45 degrees C for 120 min. Proteolytic activity increased in the presence of Ba2+ (18 +/- 1.4%) and DTT (100 mM: 36 +/- 5%), and was reduced by Co2+, Zn2+, Li+, Hg2+, Fe3+, Cu2+, Al3+, pepstatin A, and PMSF. These biochemical characteristics make this enzyme a promising candidate for use in cheesemaking. (AU)