- 學位論文
微生物生物復育過程中細胞聚集現象之研究
Cell Pellets Formation in Microbial Bioremediation
摘要
本研究主要利用菌株Rhodococcus erythropolis NTU-1的生物降解及包覆聚集能力來處理碳氫化合物。主要研究目的為探討培養過程中形成結塊包覆正十六烷之原因及其機制。實驗結果發現結塊現象的發生主要和培養基內正十六烷量和細胞量有關(其比值定義為R16)。在本實驗系統中，當R16值小於3.5時，即可能發生結塊現象。形成結塊現象時，培養基不同的R16值會形成不同的結塊構形，可能為土黃色顆粒、片狀、球狀或是乳白色顆粒、球狀。 結塊形成機制為NTU-1細胞在培養過程中以正十六烷作為細胞之間的連結物，ㄧ層一層堆疊，進而形成結塊。菌塊顆粒越大時正十六烷的包覆量越多。當結塊外層大部分為NTU-1細胞時，結塊為土黃色顆粒，而結塊外層大部分為正十六烷時，結塊為乳白色油狀顆粒。由實驗數據可支持此論點，結塊現象必須在培養基內有正十六烷殘餘時才可能發生並持續進行。 培養過程中培養基酸鹼值的下降，可能使得細胞表面疏水性增加以及細胞間電荷排斥力減少(細胞表面電位上升，在礦物培養基中NTU-1細胞表面帶負電荷)進而幫助結塊現象的發生，但兩者皆不是結塊發生的絕對因子。 本實驗定義之R16值能夠提供簡單判斷結塊現象發生之指標並且利用於石油碳氫化合物污染處裡。
並列摘要
Pure culture of Rhodococcus erythropolis NTU-1 was utilized to test the biodegradability and bioflocculate formation in treatment of petroleum pollutant. Emphasis was placed on the factors and mechanism of the formation of cell pellets during the bioremediation process. We found that the main factor of cell pellets formation was the ratio between volume of n-hexadecane and cell density in the growth medium (defined as R16). When the value of R16 was less than 3.5, formation of cell pellets might occur in the culture. Different values of R16 caused differences in morphological structures ranging from yellowish brown particles, flakes, spheres to white oily particles, spheres. The mechanism of cell pellets formation was that n-hexadecane was taken as the linkers between NTU-1 cells and to form the cell pellets by stacking up these cells during the bioremediation process. The bigger of cell pellets, the more n-hexadecane trapped in cell pellets. When the outer layers of cell pellets were covered with NTU-1 cells, the color of cell pellets was yellowish brown. But when the outer layers of cell pellets were covered with n-hexadecane, the color of cell pellets was white and oily. The data support the hypothesis that maximum agglutination of pellets requires the presense of residual amount of n-hexadecane through-out the entire process. During the bioremediation process, pH drop increased of cell surface hydrophobicity and decreased of electrostatic repulsive force among NTU-1 cells (zeta potential of NTU-1 cells of negative charge in the medium increasing from -28mV to -15mV). These changes perhaps helped to form cell pellets, but they are not the only factors of cell pellets formation. The value of R16 provided a simple indicator to morphologies of cell pellets and could be useful in petroleum pollutant treatment.