Characterization of the co-purified invertase and [beta]-glucosidase of a multifunctional extract from Aspergillus terreus

The lamentous fungus Aspergillus terreus secretes both invertase and b-glucosidase when grown under submerged fermentation containing rye our as the carbon source. The aim of this study was to characterize the co-puried fraction, especially the invertase activity. An invertase and a b-glucosidase were co-puried by two chromatographic steps, and the isolated enzymatic fraction was 139-fold enriched in invertase activity. SDS-PAGE analysis of the co-puried 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 4.06.0 and 5565 C, respectively. The invertase in co-puried enzymes was stable for 1 h at pH 3.010.0 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 Mn2 (161 %), Co2 (68 %) and Mg2 (61 %) and was inhibited by Al3, Ag?, Fe2 and Fe3?. In addition to sucrose, the co-puried enzymes hydrolyzed cellobiose, inulin and rafnose, and the apparent afnities for sucrose and cellobiose were quite similar (KM = 22 mM). However, in the presence of Mn2, the apparent afnity and Vmax for sucrose hydrolysis increased approximately 2- and2.9-fold, respectively, while for cellobiose, a 2.6-fold increase in Vmax was observed, but the apparent afnity decreased 5.5-fold. Thus, it is possible to propose an application of this multifunctional extract containing both invertase and b-glucosidase to degrade plant biomass, thus increasing the concentration of monosaccharides obtained from sucrose and cellobiose. [PUBLICATION ABSTRACT]