Screeing Of Two Alkali-Tolerant Xylanase Producing Strains And Its Optimization Of The Enzyme Production

Two strains of actinomycetes. X24-14 and X15-17, which producedalkali-tolerant xylanase were screened from the soil samples collected from a pulpmill in china, Based on the morphological, physiochemical characteristics and 16SrRNA sequence, X24-14 was priminarily identified as cellulosimicrobium cellulans;X15-17 was priminarily identified as a new species of Nocardiopsis.The investigation examined the enzyme activities which produced by X24-14and X15-17 under different pH and different temperatures. The results showed that:1) The xylanase from X24-14 had characteristic of alkali-tolerance: It remains 80%relative activity at pH ranges between pH 4.2 and pH 9.4 under 50℃. 2)Thexylanase from X15-17 also showed characteristic of alkali-tolerance, it remains 80%relative activity at pH ranges between pH 4.0and pH 9.0 under 50℃. 3) The xylanasefrom the two strains showed alkali-stable characteristics. They were stable at pHranges between pH 2.0 and pH 11.0, showing 75% of its maximal activity remainingunder 24 hours of treatment at 4℃.We also studied the effect of different growth conditions: carbon.source,nitrogen sources, inoculum size, and initial pH on the production of xylanase ofstrain X24-14. The results showed that:The optimal carbon source was wheat bran;The optima nitrogen source was peptone; The maximum xylanase activity wasachieved in the medium containing 60 g/L wheat bran, 10 g/L peptone, 7 g/LK₂HPO₄, inoculum size 5% and pH 8.5, under 37℃in 108 h.