Rhodococcus erythropolis NTU-1菌株對石油污染物之生物降解及生物吸附現象之應用

Abstract

生物復育為常見之石油污染物處理方法，但通常需要花費數周至數月的時間才能達到良好的移除效果，因此如何加速污染物移除速率為一重要之課題。本實驗室先前研究中，利用自石油污染污泥分離之Rhodococcus erythropolis NTU-1菌株獨特之生物降解和生物吸附能力，結合生物和物理移除方法，能在2天內快速移除超過90 %以上之單一組成碳氫化合污染物，如直鏈烷和異烷類。本研究主要在既有基礎上，進一步以實際應用NTU-1進行生物復育實驗。 在以高鹽度和海水批次培養實驗中，NTU-1細胞能夠維持其生物降解和生物吸附能力。在高鹽度 (1.2-3.6 % NaCl)實驗中，經過68小時培養後，能夠移除80-90 %之正十六烷 (2000 ppmv)，其中約50-60 %來自生物降解，30-35 %為生物吸附作用。在海水培養基實驗，經過140小時培養後，NTU-1亦能夠移除50 %之污染物。若添加微量NB (0.24 g/L)於培養基中，能夠有效提升污染物移除速率和縮短生物聚集體形成之時間。 在以1 % (10000 ppmv)之柴油和原油作為碳源之實驗中，NTU-1顯示能夠利用C10-C32之正直鏈烷，經過4天培養，約90 %之污染物亦能被移除，其中約30 %來自生物降解而60 %為生物吸附。此外，即便在高濃度 (1-10 %)之正十六烷情況下，NTU-1仍能維持其碳氫化合物之降解能力。 在饋料批次生物反應器系統中，在適當酸鹼值調整、通氣、培養基置換和間歇性進料等操作策略下，不論以單一碳源 (正十六烷)或混合物 (柴油和原油)，皆能夠成功操作2-4周以上且達到85 %以上的移除效率，其中約25-35 %來自生物降解而50-60 %來自於生物吸附。 此外，本研究亦發現在NTU-1進行生物復育過程中，氫離子釋放量和生物降解量呈現一線性關係，且進一步利用此關係發展一簡單估算碳氫化合物生物降解量之方法，取代傳統費時且成本較高的有機溶劑萃取並利用氣相層析儀分析之方法。 因此本實驗結果顯示Rhodococcus erythropolis NTU-1菌株的確具有良好的潛力實際應用於石油污染環境之生物復育程序中。

From our previous reports, Rhodococcus erythropolis strain NTU-1 isolated from oil-contaminated sludge efficiently removed 90 % of hydrocarbon pollutants such as normal and branched alkanes within 2 days via biodegradation and biosorption. In this study, NTU-1 was further evaluated for the purpose of practical application. R. erythropolis NTU-1 maintained its biodegradability and the formation of biofloccules characteristic under saline conditions (1.2-3.6% NaCl), as well as in sea water. After 68 h of incubation under saline conditions, 80-90 % removal of n-hexadecane (2000 ppmv) was achieved with 50-60% of biodegradation and 30-35% of biosorption. In sea water, about 50 % of n-hexadecane was removed within 140 h. Addition of NB (0.24 g/L) in culture medium facilitated the cell growth and also aggregation. Besides, in batch cultures with 1 % diesel or crude oil, approximately 90% removal was achieved within 4 days (about 30 % of biodegradation and 60 % of biosorption). NTU-1 could degrade C10–C32 of n-alkanes in diesel oil or crude oil. Moreover, NTU-1 utilized the n-hexadecane at relatively high concentration (1-10 %) with fast degradation rate. In bioreactors with aeration, medium exchange and pH adjustment, an intermittent feed (42000 ppmv n-hexadecane; 35000 ppmv diesel and crude oil) resulted in approximately 85-90 % removal within 2-4 weeks (25-35% of biodegradation and 50-60 % of biosorption). During the biodegradation, the amount of H+ ions released corresponded well to the carbon-chain length of the n alkanes (either n-tetradecane, n-hexadecane or n-octadecane). With the relationship, n-alkanes consumption could be reasonably estimated by monitoring pH changes in the medium. This procedure presented a convenient alternative as compared with some complex or expensive method such as organic solvent extractions and gas chromatography analysis. The amount of H+ ions released correlated well with the carbon-chain length of the n alkanes. The results showed that Rhodococcus erythropolis NTU-1 possessed great potential in bioremediaition process of sites polluted with petroleum pollutants.