초록
<P><I>Streptomyces misionensis</I> strain PESB-25 was screened and selected for its ability to secrete cellulases. Cells were grown in a liquid medium containing sugarcane bagasse (SCB) as carbon source and corn steep liquor (CSL) as nitrogen source, whose concentrations were optimized using response surface methodology (RSM). A peak of endoglucanase accumulation (1.01 U<I>·</I>mL<SUP>−1</SUP>) was observed in a medium with SCB 1.0% (w/v) and CSL 1.2% (w/v) within three days of cultivation. <I>S. misionensis</I> PESB-25 endoglucanase activity was thermoacidophilic with optimum pH and temperature range of 3.0 to 3.6 and 62° to 70°C, respectively. In these conditions, values of 1.54 U mL<SUP>−1</SUP> of endoglucanase activity were observed. Moreover, Mn<SUP>2+</SUP> was demonstrated to have a hyperactivating effect on the enzyme. In the presence of MnSO<SUB>4</SUB> (8 mM), the enzyme activity increased threefold, up to 4.34 U<I>·</I>mL<SUP>−1</SUP>. Mn<SUP>2+</SUP> also improved endoglucanase stability as the catalyst retained almost full activity upon incubation at 50°C for 4 h, while in the absence of Mn<SUP>2+</SUP>, enzyme activity decreased by 50% in this same period. Three protein bands with endoglucanase activity and apparent molecular masses of 12, 48.5 and 119.5 kDa were detected by zymogram.</P>