Production and improved bleaching abilities of a thermostable xylanase from a newly isolated Streptomyces chartreusis strain

Abstract

A Streptomyces chartreusis strain L1105 capable of producing extra-cellular xylanase was isolated and identified in this study and the production conditions optimized. The xylanase activities obtained were 121, 137 and 334 U/ml, when using birch wood xylan, beech wood xylan and corncobs xylan respectively, as substrates. Production of xylanase by L1105 on corncobs xylan was enhanced by optimizing the nitrogen source, growth temperature and initial pH of the culture medium. The effect of surfactants (Tween 80) on xylanase production was investigated and the maximum production was observed at a concentration of 0.2% (v/v). After optimization of various production parameters, the maximum xylanase yield (731 U/ml) was obtained at 40°C using 2.5% corncobs xylan as substrate for 7 days of cultivation. Furthermore, the potential application of the xylanase was evaluated in wheat straw pulp, from which the amount of reducing sugars released by the xylanase increased significantly with time. Enzymatic pre-bleaching of wheat straw pulp showed a 12% reduction in the kappa number of the pulp. We are the first to demonstrate that the S. chartreusis strain has the capacity for xylanase production, although, many other xylanase-producing microorganisms have been reported.

Key words: Streptomyces chartreusis, xylanase, submerged fermentation, production parameters.