Purification and Partial Characterization of Alkaline Xylanase from Escherichia coli Carrying pCX311

Abstract

Xylanase produced by E. coli HB101 carrying plasmid pCX311, which contains the xylanase A gene of alkalophilic Bacillus sp. strain C-125, was purified by ammonium sulfate precipitation, DEAE-cellulose column chromatography and Sephadex G-75 gel filtration. The purified enzyme had a molecular weight of 43, 000. The pH and temperature optima for its activity were 6-10 and 70°C, respectively. The enzyme retained full activity after incubation at 50°C for 10min. These enzymatic properties of the xylanase were almost the same as those of xylanase A. But this enzyme was less stable than xylanase A at low pHs. Furthermore, we could purify a larger amount of alkaline xylanase from E. coli than from alkalophilic Bacillus sp. strain C-125.