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|標題:||Studies on the optimal production of xylanase from Aspergillus carneus M34|
Aspergillus carneus M34生產聚木糖最適化條件之探討
|摘要:||Hemicellulose is abundant in nature and consists largely of xylan. It can be hydrolyzed by xylanase to xylooligosaccharides and xylose which can serve as sweetener or even be converted to chemicals, organic solvents and other useful products. Plant biomass seems to be a good renewable resource if we use it well. In this study, Aspergillus carneus M34, which was isolated from soil by our laboratory and had ability to produce xylanase, was used to study the production and characterization of xylanase.
Aspergillus carneus M34 was cultivated in shaking flasks and a better medium for xylanase production was determined by response surface methodology as follows: birchwood xylan, 1.5%; peptone, 0.6%; Tween 80, 0.2%; KH2PO4, 0.2%; CaCl2, 0.03%; MgSO4∙7H2O, 0.03%; FeSO4∙7H2O, 0.0005%; MnSO4∙H2O, 0.00016%; ZnSO4∙7H2O, 0.00014%; CoCl2, 0.0002%. For cultivation condition, initial pH at pH 8.6, incubation temperature at 40℃, and a shaking rate at 130 rpm showed a better result in enzyme production. The maximal xylanase activity of 48 U/mL was obtained after 3 days of incubation under the above conditions. The optimal pH of crude xylanase activity was pH 7.0, and the optimal temperature for this enzyme was 50-60℃. The results of thermostability study of this enzyme showed that 50% of activity was retained after incubated at 50℃ for 1h; however nearly no activity was found when the crude enzyme was incubated at 60℃ for 1h. The activities of A. carneus M34 xylanase showed high specificity on hydrolysis of xylans which come from birchwood and oat spelt.|
半纖維素在自然界中大量存在，其中主要構成物為聚木糖，可利用聚木糖加以降解成為木寡糖、木三糖、木二糖或木糖。除了可當作甜味劑之外還可進一步轉化成各類化學藥品及有機溶劑等，達到資源開發與回收的目的。本研究主要針對本實驗室自土壤中篩出具聚木糖活性之Aspergillus carneus M34進行探討，希求得其生產聚木糖的較適液態培養條件， 除利用RSM找出最適培養基組成，並探討粗酵素液之性質。 經過較適液態培養條件的探討及RSM的試驗，生產A. carneus M34聚木糖之最適培養條件其結果如下：碳源以1.5﹪birchwood xylan，氮源以0.6﹪peptone為最佳，Tween 80, 0.2%；KH2PO4, 0.2%；CaCl2, 0.03%；MgSO4∙7H2O, 0.03%；FeSO4∙7H2O, 0.0005%；MnSO4∙H2O, 0.00016%；ZnSO4∙7H2O, 0.00014%；CoCl2, 0.0002%。起始pH值調為pH 8.6，培養溫度為40℃，震盪速率為130 rpm，培養至第三天即有較佳聚木糖產量（約48 U/mL）。在粗酵素液性質之部份，此酵素之最適作用pH值為pH 7.0，而且也在pH 7.0的環境下最為穩定。此酵素之最適作用溫度為50-60℃。熱穩定性方面，此酵素於50℃作用一個小時仍能保有50﹪之活性，然在60℃以上一個小時則幾乎完全失去活性。A. carneus M34聚木糖的基質特異性很高，只對由木糖構成之聚合物如樺木或燕麥聚木糖具有高活性，對於非木糖構成之物質則活性極低。
|Appears in Collections:||食品暨應用生物科技學系|
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