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Title: ENDOXYLANASE FROM A NEWLY ISOLATED CORN FIBER XYLAN UTILIZING FUSARIUM VERTICILLIOIDES

Author
item Saha, Badal

Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn fiber represents a renewable resource that is available in sufficient quantities from the corn wet milling industry to serve as a low cost feedstock for production of fuel ethanol and other value-added fermentation products. For this, the corn fiber has to be broken down to simple sugars (saccharification). The structure of xylan in corn fiber is very complex, and commercially available enzyme preparations do not effectively hydrolyz it to simple sugars. Thus, this research was undertaken to isolate an organism that can produce enzymes for saccharification of corn fiber xylan. Endoxylanase is a key enzyme for xylan hydrolysis. The enzyme from a newly isolated fungal strain that can utilize corn fiber xylan as growth substrate has been purified and characterized. It also has potential for use in the production of xylooligosaccharides from xylan substrates which may be useful to improve animal feed digestibility by hydrolyzing a major component of animal feed.

Technical Abstract: A fungus, Fusarium verticillioides (NRRL 26518), was isolated by screening soil samples using corn fiber xylan as carbon source. The extracellular xylanase from this fungal strain was purified to apparent homogeneity from the culture supernatant by ultrafiltration using a 30,000 cut-off membrane, octyl-Sepharose chromatography and Bio gel A-0.5m gel filtration. The purified xylanase (specific activity 492 U/mg protein, MW 24,000, isoelectric pH 8.6) displayed an optimum temperature at 50 deg C and optimum pH at 5.5, a pH stability range from 4.0 to 9.5 and thermal stability up to 50 deg C. It hydrolyzed a variety of xylan substrates mainly to xylobiose and higher short-chain xylooligosaccharides, indicating that the enzyme was an endoxylanase. No xylose was formed. The enzyme did not require metal ions for activity and stability.