Resumo

Proteases are the most important group of commercially produced enzymes and are used in different processes,i.e. in detergents, foods, pharmaceuticals, leather, cosmetics, brewing, silk an for recovery of silver from used X-ray films. Fungi produce a variety of proteolytic enzymes. They have important medical, pharmaceutical and cosmetic applications. Recently, the use of alkaline protease as an industrial catalyst has increased. These enzymes exhibit high catalytic activity and are economically feasible. Proteases of fungal origin have advantages such as low material costs coupled with high productivity, faster production, the ease in which the enzymes can be modified and the mycelium can be easily removed by filtration. The goal of this work was to investigate the proteases production by fungi isolated from Brasilian Savanna soil. Production of proteases by a newly isolated Penicillium fellutanum was studied using submerged fermentation under shaking. These fungi were cultivated for 15 days at 28•C in a medium containing: peptone 2%, Sabouraud dextrose broth 3%, yeast extract 2% and casein 2%.Parameters such as biomass, glucose consumption, pH and protease activity were determined. During this period samples were taken from the broth and a induction curve for this enzyme was built. Protease activity was determined using a solution of azocasein at pH 5.0 as substrate and 37•C during the whole reaction. One enzymatic unit was defined as the amount of enzyme that produced an increase of 0.001 absorbance units for a reaction in 40 min.The growth profile of the fungus P.fellutanum showed enzymatic activity from the third day of incubation, when the culture was in the exponential growth phase. Generally, the synthesis and secretion of proteases is initiated during the exponential phase of growth with maximal production on stationary phase. The maximum protease activity occurred in the 7th, 8th and 15th days (10.03, 10.12 and 11.20 U/mL, respectively). The pH was basic during those days with values of 8.8, 8.9 and 8.3, respectively. The analysis of nutrient consumption in all cultures showed that glucose was depleted in 72h. It was observed that maximum activity occurred when the glucose concentration of the medium was found exhausted.