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High Cell Density Culture of Rhodococcus erythropolis KA 2-5-1 for in situ Induction of Dibenzothiophene Degrading Activity

Rhodococcus erythropolis KA2-5-1菌體高密度培養及原位誘導二苯並塞吩(DBT)降解活性

摘要


本文為了獲得高的二苯並塞吩(DBT)降解活性的細胞,我們實現了Rhodococcus erythropolis KA2-5-1細胞兩物象流加培養,在培養過程中,向培養液中添加硫酸鹽作為硫源,並添加DBT以誘導菌體分泌DBT 降解?,培養開始30小時後,可以測出細胞的濃度達到24.3 g/L,誘導10小時後獲得18.2 mmol/kg-dry cells/h的最高比降解活性,為了降低培養系統的複雜度和培養費用,試驗中,通過對硫酸鹽離子的濃度的限制,使菌株只能在硫酸鹽飢餓培養時才能誘導?活性,菌株以流加培養的方式,在硫酸鹽濃度為96 mg/L的培養液中培養,培養22小時後,硫酸鹽濃度降到低於10 mg/L,並得到大約10 g/L菌體濃度的菌體,此時向培養液中添加125 mg/L的DBT,通過對培養殘液中的殘餘培養液成分的濃度分析得知,培養結束後,鐵和鎂離子都被耗盡,因此,在之後的流加培養時添加一定濃度的鐵和鎂離子濃縮液,培養開始23小時後,向培養液中添加125 mg/L的DBT,?活性迅速增高,在這次試驗中降解活性沒有下降,並在34小時後獲得18.5 mmol/kg-dry cells/h的最高比降解活和41.7 g/L菌體濃度的菌體。

關鍵字

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並列摘要


To obtain cells with high dibenzothiophene (DBT) degrading activity, two phase fed-batch culture of Rhodococcus erythropolis KA2-5-1 was carried out, which consisted of growth phase in the medium containing sulfate ion as a sulfur source and induction phase for expression of DBT degrading enzyme by DBT addition. Cell concentration of 24.3 g/L was obtained after 30 h culture and the maximum specific degrading activity of 18.2 mmol/kg-dry cells/h was achieved at 10 h after induction. In order to simplify the system and lower an operational Cost, next, in situ induction of the enzyme activity was conducted by means of sulfur limitation since the strain can only be induced under sulfur starvation. The strain was cultivated in fed-batch mode in the modified A medium containing 96 mg/L of sulfate ion. At 22 h, sulfate concentration decreased below 10 mg/L and approximately 10 g/L of cell concentration was obtained. When 125 mg/L of DBT was added at 22 h, the enzyme activity increased rapidly and the maximum specific activity of 14.3 mmol/kg-dry cells/h was obtained at 28 h. However, the DBT degrading activity decreased rapidly thereafter. From the assay of remaining concentration of medium components in the culture broth, it was found that Fe and Mg ions were exhausted at the end of cultivation. Fed-batch culture with feeding of concentrated solution of Fe and Mg ions was then conducted. After 23 h, 125 mg/L of DBT was added, and the enzyme activity increased rapidly. In this case, the activity did not decrease, and the maximum specific degrading activity of 18.5 mmol/kg-dry cells/h and cell concentration of 41.7 g/L were obtained at 34 h.

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