Characterization of the co-purified invertase and ß-glucosidase of a multifunctional extract from Aspergillus terreus.

The filamentous fungus Aspergillus terreus secretes both invertase and ß-glucosidase when grown under submerged fermentation containing rye flour as the carbon source. The aim of this study was to characterize the co-purified fraction, especially the invertase activity. An invertase and a ß-glucosidase were co-purified by two chromatographic steps, and the isolated enzymatic fraction was 139-fold enriched in invertase activity. SDS-PAGE analysis of the co-purified enzymes suggests that the protein fraction with invertase activity was heterodimeric, with subunits of 47 and 27 kDa. Maximal invertase activity, which was determined by response surface methodology, occurred in pH and temperature ranges of 4.0-6.0 and 55-65 °C, respectively. The invertase in co-purified enzymes was stable for 1 h at pH 3.0-10.0 and maintained full activity for up to 1 h at 55 °C when diluted in water. Invertase activity was stimulated by 1 mM concentrations of Mn²âº (161 %), Co²âº (68 %) and Mg²âº (61 %) and was inhibited by Al³âº, Ag⁺, Fe²âº and Fe³âº. In addition to sucrose, the co-purified enzymes hydrolyzed cellobiose, inulin and raffinose, and the apparent affinities for sucrose and cellobiose were quite similar (K(M) = 22 mM). However, in the presence of Mn²âº, the apparent affinity and V(max) for sucrose hydrolysis increased approximately 2- and 2.9-fold, respectively, while for cellobiose, a 2.6-fold increase in V(max) was observed, but the apparent affinity decreased 5.5-fold. Thus, it is possible to propose an application of this multifunctional extract containing both invertase and ß-glucosidase to degrade plant biomass, thus increasing the concentration of monosaccharides obtained from sucrose and cellobiose.

Thermostable invertases from Paecylomyces variotii produced under submerged and solid-state fermentation using agroindustrial residues.

The filamentous fungus Paecylomices variotii was able to produce high levels of cell extract and extracellular invertases when grown under submerged fermentation (SbmF) and solid-state fermentation, using agroindustrial products or residues as substrates, mainly soy bran and wheat bran, at 40°C for 72 h and 96 h, respectively. Addition of glucose or fructose (≥1%; w/v) in SbmF inhibited enzyme production, while the addition of 1% (w/v) peptone as organic nitrogen source enhanced the production by 3.7-fold. However, 1% (w/v) (NH(4))(2)HPO(4) inhibited enzyme production around 80%. The extracellular form was purified until electrophoretic homogeneity (10.5-fold with 33% recovery) by DEAE-Fractogel and Sephacryl S-200 chromatography. The enzyme is a monomer with molecular mass of 102 kDa estimated by SDS-PAGE with carbohydrate content of 53.6%. Optima of temperature and pH for both, extracellular and cell extract invertases, were 60°C and 4.0-4.5, respectively. Both invertases were stable for 1 h at 60°C with half-lives of 10 min at 70°C. Mg(2+), Ba(2+) and Mn(2+) activated both extracellular and cell extract invertases from P. variotii. The kinetic parameters K(m) and V(max) for the purified extracellular enzyme corresponded to 2.5 mM and 481 U/mg prot(-1), respectively.