| In this study, Time course of xylanase' production was studied by culturing Strepotmyces albus and Saccharomonospora viridis in different substrates. The results showed that xylanase demonstrated different activities in different substrates. In the aspect of induction of xylanase, the wood powder was better than xylan, while the compound substrate was better than the single one. After Strepotmyces albus having been cultured for 144 h in the optimal enzyme-induction medium, the production of xylanase culminates, with its maximal enzyme activity of 45.66U/mL. The results showed that the xylanase from Strepotmyces albus had the characteristics of both thermotolerance and alkali-tolerance, showing 48.15% of its maximal activity remaining under 3 hours of treatment at 90℃, and the highest activity in pH 7.0.After Saccharomonospora viridis having been cultured for 156h in the optimal enzyme-induction medium, the production of xylanase attained the high peak, with its maximal enzyme activity of 45.14U/mL.The experiment results suggested that the xylanase from Saccharomonospora viridis had the characteristics of both thermotolerance and alkali-tolerance, showing the remaining 63.55% of its maximal activity under 3 hours' treatment at 90℃, and the highest activity in pH7.0.Through the comparison of these two strains, we can conclude that the xylanase from the both ones had the characteristics of both thermotolerance and alkali-tolerance, and was suitable for the pulp biobleaching. But the xylanase from Saccharomonospora viridis had almost the same activity as the one from Strepotmyces albus while its cellulase' activity was lower than the latter, In addition, Saccharomonospora viridis could produce xylanase in a high lever in a longer time. Although its xylanase's alkali-tolerance was equal to the xylanase from Strepotmyces albus, but the thermotolerance was much better than the latter, so we selected Saccharomonospora viridis as the better experiment strain.
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