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The objectives of the present study were isolation, identification and characterization of xylanase producing fungi, optimization of medium composition and cultural conditions for xylanase enzyme production using cheaper sources. The fungal strains were isolated from garden soil by serial dilution technique and Aspergillus niger was identified and isolated in pure form. In conformation screening by congo red test, based on the reddish zone of enzyme activity formation in oat spelt xylan agar plates, A. niger was selected and optimized for xylanase enzyme production in solid state fermentation using cheaper sources like wheat bran, rice bran, soya bran, ragi bran and saw dust. Maximum enzyme activity was observed in wheat bran (9.87 U/ml). The use of wheat bran as a major carbon source is particularly valuable because oat spelt xylan or birch wood xylan are more expensive. The effects of time course, incubation substrate, inoculum size, moisturizing agent, moisture content, temperature and volume of fermentation medium on the production of xylanase were studied. The maximum xylanase production (12.65 U/ml) was observed at optimized condition, incubation temperature of 28°C after 6 days of incubation period while minimum production (9.38 U/ml) at unoptimized condition. The maximum production of enzyme was found to be in wheat bran when the volume of fermentation medium was kept as 10 g/250 ml conical flasks, with mineral solution as moisturizing agent and moisture ratio 1:0.7. Thus the present study proved that the fungal strain A. niger used is highly potential and useful for xylanase production.
Xylanase production by a newly isolated Aspergillus niger SS7 was studied in submerged culture. The optimum initial pH for xylanase production was found to be 7.0. Different agricultural and industrial wastes were evaluated for their ability to induce xylanase production by this isolate. The best xylanase production (293.82 IU/ml) was recorded at 3% (w/v) corn cob hulls after 120 h of incubation. The Aspergillus niger SS7 isolate grown in a simple medium, proved to be a promising microorganism for xylanase production.
The restriction of PCR-amplifïed internal transcribed spacers (ITS) of ribosomal DNA was used to confirm the genetic variation among 22 isolates of Cochliobolus sativus differing in their xylanase production. Results show a high level of diversity of ITS-RFLP markers among the isolates. The molecular parameter used showed that C. sativus isolates reside in three phylogenetic groups. There was observed the resolution between clustering of isolates and their xylanase production level.
Fusarium sp. has been shown to be a promising organism for enhanced production of xylanases. In the present study, xylanase production by 21 Fusarium sp. isolates (8 Fusarium culmorum, 4 Fusarium solani, 6 Fusarium verticillioides and 3 Fusarium equiseti) was evaluated under solid state fermentation (SSF). The fungal isolate Fusarium solani SYRN7 was the best xylanase producer among the tested isolates. The effects of some agriculture wastes (like wheat straw, wheat bran, beet pulp and cotton seed cake) and incubation period on xylanase production by F.solani were optimized. High xylanase production (1465.8 U/g) was observed in wheat bran after 96 h of incubation. Optimum pH and temperature for xylanase activity were found to be 5 and 50°C, respectively.
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