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標題: Aspergillus niger NCH-3聚木糖酶之生產及其在低聚木糖製備之應用
Production of xylanase by Aspergillus niger NCH-3 and its application on the preparation of the xylooligosaccharides
作者: 陳丹桂
Tan-Kuei, Chen
關鍵字: Aspergillus niger NCH-3
Aspergillus niger NCH-3
chemical modification
出版社: 食品科學系
摘要: 半纖維素在自然界中含量豐富,其主要成份為聚木糖,目前仍屬於低度開發利用之資源。本研究針對一具有生產聚木糖酶能力之真菌分離株Aspergillus niger NCH-3,探討其擴大培養之較適培養基pH值、攪拌速率及酵素催化特性。另外,亦探討以自行萃取之茭白筍殼半纖維素為基質,與聚木糖酶之水解特性;並嘗試以活性炭進行水解產物之分離回收。 以五公升桌上型發酵槽進行Asp. niger NCH-3之擴大培養,以1%茭白筍殼半纖維素、1%玉米浸漬液和0.38% KNO3為基本培養基,在pH 6.0,培養溫度35℃,攪拌速率170~200 rpm和通氣量1vvm下培養5天,所得最高酵素活性為28.56 U/ml。 以粗酵素液或經硫酸銨劃分之聚木糖酶進行化學修飾,其中修飾劑會對於酵素中tryptophan、histidine和arginine等胺基酸殘基產生抑制,推論此三者在酵素活性表現或是基質鍵結部位佔重要地位。 在不同pH值下,Asp. niger NCH-3聚木糖酶的水解能力有所不同,以pH 4.0-5.0的效果較佳;此外,添加2.5 g/L的非離子型界面活性劑Tween 20有助酵素水解能力。 活性炭和矽藻土以2:1之比例吸附低聚木糖之效果較佳;其中又以連續式分離回收效果較佳。當以5%酒精沖提時,可將木二糖溶離出,回收率約90.36%。
Hemicelluloses, which comprise mainly xylans, are abundant biomass resources in the nature. However, xylans remain to be a less utilized resource. Xylanase production from a fungal isolate, Aspergillus niger NCH-3 was used in this study. The objectives of this work were to determine the optimum pH and agitation rate for cultivation of cells using a 5 L bench-top bioreactor. In addition, some catalytic properties of Asp. niger NCH-3 xylanase using coba husk hemicellulose as substrate, and separation of the xylooligosaccharides by activated charcoal were also studied. Asp. niger NCH-3 was cultivated in a medium containing 1% coba husk hemicellulose, 1% corn steep liquor, and 0.38% KNO3 at 35℃ for 5 days. The maximum xylanase activity with 28.56 U/ml was obtained at pH 6.0 with 170~200 rpm agitation rate, and aerated at 1.0 vvm. Crude or ammonium sulfate precipitation-purified xylanase were chemically modified by different chemical reagents. The tryptophan, histidine and arginine residues in xylanase molecule was inactivated by some specific reagents. This indicated that tryptophan, histidine and arginine residues were involved in the active site or substrate binding site of the enzyme. Degree of hydrolysis of coba husk hemicellulose by the xylanase from varied slightly with different pH values, the pH values ranged from 4.0 to 5.0 for optimum hydrolysis condition. Presence of 2.5 g/L of nonionic surfactant Tween 20 increased hydrolysis ability of xylanase. Combination of activated charcoal-celite (2: 1, w/w) was chosen for adsorption and separation of xylooligosaccharides from hydrolysates of coba husk hemicellulose, and the continuous mode was superior to batch mode in the elution of sugars adsorbed. Up to 90.36% of xylobiose could be recovered from the absorbed sugars by using 5% alcohol as an eluant.
Appears in Collections:食品暨應用生物科技學系



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