Xylanase production by Bacillus polymyxa

Bacillus polymyxa produced high levels (12–13 U cm−3) of extracellular xylanases when grown in a complex medium containing yeast extract and oat spelt xylan as nitrogen and carbon sources respectively. Substantially lower yields of enzyme were produced during growth on the monosaccharides glucose, arabinose and xylose. Meagre growth occurred when ammonium sulphate, instead of yeast extract, was used as nitrogen source. When assayed in culture broth supernatants, xylanase showed an optimum activity in 48°C and at pH values in the range 5.0–6.5. Under such conditions, the half‐life of this xylanase preparation was 8 h. Mn2+ showed a strong inhibitory effect on the enzyme, but inhibition by EDTA (27% w/v) suggested dependence on a metallic ion. SDS‐PAGE and zymogram overlay showed that up to five separate xylanases in the range of 20 to 116 kDa were produced.