Characterization of Xylanase Produced by Aspergillus niger Fermented on Corn Cob | ||
| Egyptian Journal of Microbiology | ||
| Article 5, Volume 46, Issue 1, December 2011, Pages 79-94 PDF (371.23 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/ejm.2011.264 | ||
| Abstract | ||
| THE USE of waste as a raw material is important for government economy and natural balance. This article investigates a strain of Aspergillus niger for xylanase production in solid state fermentation (SSF) using different agricultural residues without pretreatment. The organism produced 164.4 (µ mol/ ml/ min) of xylanase in a static flask on a corn cob, an inexpensive lignocellulosic biomass, without enrichment of medium (only distilled water). Using surfactant solution (Tween 80, 1%) for enzyme extraction from solid substrate increased the yield by 52.5 %. Maximum xylanase activity was recorded at 55°C, with high activity at a wide range of temperature (50 - 60°C). The enzyme produced on corn cob showed good thermal stability with residual activity of 62.1 and 54.3 % after 2 hr incubation at 50 and 60°C, respectively. The addition of glycerol (50 %) improved stability against temperature by 19.9 % after incubation at 60°C for 1hr, and 17.8 % after incubation at 60°C for 2 hr. The optimum pH for the enzyme activity was 4.5, increasing pH causing decreasing in activity. Xylanase enzyme was stable at different pH’s after 1 hr with a remaining activity of 89.6 % and 55.0 %, respectively at pH 4.0 and 9.0. The enzyme possessed 70.6 and 37.6 % of its activity by storage at room temperature after 10 and 30 days. In the presence of metal ions such as Na2+, Ca2+ and protein disulphide reducing agents such as dithiothreitol (DTT), the activity of the enzyme was increased by 34.9, 10.7 and 32.8 %, respectively. Sodium dodecyl sulphate (SDS) and Cu2+ ion strongly inhibited the enzyme by 56.8 and 23.7 %, respectively. Saccharification of different wastes by the enzyme was studied. The highest yield of reducing sugars (20.3 mg/ 200 mg dry weight substrate) was obtained from corn cob with maximum saccharification after 72 hr (71.8 %) as compared to other wastes. | ||
| Keywords | ||
| Lignocellulosic biomass; xylanase; stability; saccharification | ||
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