Comparação do perfil catalítico e termodinâmico de diferentes β-glicosidases fúngicas

Abstract

β-glycosidases are enzymes that catalyze the hydrolysis of cellobiose, the glucose dimer resulting from the action of cellulolytic enzymes on the cellulose molecule, releasing free glucose that can be used in fermentative processes to produce ethanol, these enzymes are capable of breaking bonds glycosides of terpenes found in the grape, increasing the volatility of these compounds, and in the deglycosylation of isoflavones present in soybean, favoring the absorption of these compounds by the human intestine. The objective of the present study was to optimize parameters for the cultivation of Lichtheimia corymbifera (mesophile) and Byssochlamys spectabilis (thermophilic) for the production of β-glycosidases and to compare the catalytic and thermodynamic properties of the partially purified enzymes. The maximum amount of β-glycosidase produced by L. corymbifera was 39 U / g of dry substrate (or 3.9 U / mL) and that of B. spectabilis was 77 U / g (or 7.7 U / mL ). The optimum pH and temperature were 4.5 and 55 ° C and 4.0 and 50 ° C for the enzyme L. corymbifera and B. spectabilis, respectively. The β-glycosidase produced by L. corymbifera remained stable at pH between 4.0 and 7.5, while the B. spectabilis enzyme remained stable at pH between 4.0 and 6.0. In relation to thermostability, β-glycosidases produced by B. spectabilis remained stable for 1 h at 50 ° C, and that of L. corymbifera was active for 1 h at 45 ° C. The determination of the thermodynamic parameters confirmed the higher thermostability of the enzyme produced by the thermophilic fungus B. spectabilis, which presented higher values of ΔH, activation energy for denaturation (Ea) and halflife t (1/2). The enzymes were stable in the presence of ethanol and were competitively inhibited by glucose. These characteristics contribute to its use in simultaneous saccharification and fermentation of plant biomass.