Investigation of Liquid and Solid Fermentation Processes of the Fungus Aspergillus fumigatus for Protease Production

Abstract

The production of microbial enzymes obeys the proper conditions of each microorganism species and the means applied to fermentation, being subject to the differences between liquid and solid fermentations. This way, filamentous fungi have been widely exploited as a productive source of proteases due to their growth capacity and a wide production range. The fungus A. fumigatuswas isolated from the soil having decaying wood. Production studies were conducted through liquid-state fermentation in Erlenmeyer flasks of 250mL with 50mL containing KH2PO4, 0,7%; K2HPO4, 0,2%; MgSO4.7H2O, 0,01%; citrate 2H2O, 0,05%; yeast extract, 0,1%; CaCl2.2H2O, 0,01% and peptone 1% with supplementation of casein and glucose. The solid fermentation was performed in Erlenmeyer flasks of 250mL using wheat bran as a substrate adding protein supplementation, e.g. ovalbumin. The partial characterization was donewithpartially-purified enzyme throughethanol precipitation. The partial characterization was done by using azocasein as a substrate. The peak protease production in liquid fermentation was of 96hours, the same production period obtained for the solid one. The protease resulted from liquid fermentation presented pH and optimumtemperatureof 8,0 and50 ◦C, respectively and thermostability of 50% after a 60-minute incubation at 45 ◦C, and belongs to the class of the serine proteases. The protease obtained from solid fermentation presented pH and optimum temperature of 8,0 and 50 ◦C, respectively and thermostability of 75% at 45 ◦C for 60minutes.Weconclude that theproteasesproducedby the fungus A. fumigatus in liquid and solid fermentation processes present the same biochemical characteristics, except for the thermostability. Future experiments of purification and biochemical characterizationwill be carried out for protease obtained by solid fermentation. Financial support: FAPESP N◦ 2008/11303-6.