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. Substant ially lower yields of enzyme were produced during growth on the monosa ccharides glucose, arabinose and xylose. Meagre growth occurred when a mmonium sulphate, instead of yeast extract, was used as nitrogen sourc e. When assayed in culture broth supernatants, xylanase showed an opti mum activity in 48-degrees-C and at pH values in the range 5.0-6.5. Un der such conditions, the half-life of this xylanase preparation was 8 h. Mn2+ showed a strong inhibitory effect on the enzyme, but inhibitio n 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.