Xylanase production by <i>Thermomonospora curvata</i>

Abstract

F.J. STUTZENBERGER AND A.B. BODINE. 1992. The thermophilic actinomycete, Thermomonospora curvata , produced &lt;1 xylanase U/mg dry cell weight during growth in minimal medium with soluble sugars, 3–7 U/mg on purified xylan or cellulose and 28 U/mg on cotton fibres. The optimal growth temperature for xylanase production was 55°C. Cell‐bound xylanase decreased from about 30% of total activity in early culture to about 2% in stationary phase. Fractionation of extracellular proteins by isoelectric focusing and size exclusion chromatography yielded three endoxylanases (XI, X2 and X3) with pI and mol. wts of pH 4.2, 7.1 and 8.4 and 36, 19 and 15 kDa respectively. X1, X2 and X3 had similar pH optima (7.8, 7.2 and 6.8) and K m for xylan (2.5, 1.4 and 2.0 mg/ml) respectively, but differed in their thermostability; half‐lives at 75°C were 21 h for X1, 151 h for X2 and 302 h for X3.