Streptomyces misionensis PESB-25 Produces a Thermoacidophilic Endoglucanase Using Sugarcane Bagasse and Corn Steep Liquor as the Sole Organic Substrates

Abstract EN

Streptomyces misionensis 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·mL−1) was observed in a medium with SCB 1.0% (w/v) and CSL 1.2% (w/v) within three days of cultivation.

S.

misionensis 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−1 of endoglucanase activity were observed.

Moreover, Mn2+ was demonstrated to have a hyperactivating effect on the enzyme.

In the presence of MnSO4 (8 mM), the enzyme activity increased threefold, up to 4.34 U·mL−1.

Mn2+ also improved endoglucanase stability as the catalyst retained almost full activity upon incubation at 50°C for 4 h, while in the absence of Mn2+, 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.