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.
Highlights
Xylans account for 20 to 35% of the total dry weight of hardwoods and annual plants and represent a vast resource that can be used for production of fermentable sugars and fuels as described previously (Filho, 1998)
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
We are the first to demonstrate that the S. chartreusis strain has the capacity for xylanase production, many other xylanase-producing microorganisms have been reported
Summary
Xylans account for 20 to 35% of the total dry weight of hardwoods and annual plants and represent a vast resource that can be used for production of fermentable sugars and fuels as described previously (Filho, 1998). The complete cleavage of xylan is carried out by the synergistic action of -xylanase and its accessory enzymes, including -xylosidase, -arabinofuranosidase,. In recent years, increasing concern over preserving resources and environment has initiated a growing interest in producing microbial enzymes. Xylanases from microorganisms have attracted a great deal of attention because of their biotechnological potential in various industrial processes such as food, feed and paper-pulp industries. Xylan-degrading enzymes produced by a wide variety of fungal species have been reported to be used in biobleaching of kraft pulps, such as Thermomyces lanuginosus (Li et al, 2005), Penicillium janthinellum (Oliveira et al, 2006), Arthrobacter sp. (Khandeparkar and Bhosle, 2007), Streptomyces cyaneus (Ninawe et al, 2008) et al little research on xylanase from S. chartreusis has been reported. Xylan-degrading enzymes produced by a wide variety of fungal species have been reported to be used in biobleaching of kraft pulps, such as Thermomyces lanuginosus (Li et al, 2005), Penicillium janthinellum (Oliveira et al, 2006), Arthrobacter sp. (Khandeparkar and Bhosle, 2007), Streptomyces cyaneus (Ninawe et al, 2008) et al little research on xylanase from S. chartreusis has been reported.
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