Purification and properties of two thermostable alkaline xylanases from an alkaliphilic bacillus sp

Two xylanases, designated XylA and XylB, were purified from the culture supernatant of the alkaliphilic Bacillus sp. strain AR-009. The molecular masses of the two enzymes were estimated to be 23 kDa (XylA) and 48 kDa (XylB) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The optimum pHs for activity were 9 for XylA and 9 to 10 for XylB. The temperature optima for the activity of XylA were 60 degreesC at pH 9 and 70 degreesC at pH 8. XylB was optimally active at 75 degreesC at pH 9 and 70 degreesC at pH 8. Both enzymes were stable in a broad pH range and showed good stability when incubated at 60 and 65 degreesC in pH 8 and 9 buffers.