利用混合菌株（TN-4）與單一菌株（Rhodococcus erythropolis NTU-1）處理正十六烷之研究

Abstract

石油為世界上主要的能源, 但同時也給人類生存的環境帶來了嚴重污染，因此要如何降低石油碳氫化合物對環境的影響是非常重要的。本研究主要探討TN-4混合菌株與Rhodococcus erythropolis NTU-1單一菌株在（1）不同正十六烷濃度與（2）不同初始培養基酸鹼值下對正十六烷所呈現的生物降解能力以及烷類包覆能力。 從實驗觀察顯示，TN-4的生長會隨著烷類濃度的增加而提高，但其生物降解量在高濃度基質的情況下卻沒有顯著的提升。反觀NTU-1單一菌株，其生長與生物降解能力，並不會受到正十六烷濃度變化之影響。在探討最佳初始培養基酸鹼值的實驗中（正十六烷濃度為1470ppm），我們發現實驗進行66小時後，TN-4與NTU-1均能在pH 7.5的環境下移除近100%的正十六烷，達到最好的總移除效率。 此外，TN-4與NTU-1在降解烷類的過程中會慢慢聚集成0.1~2cm的細菌顆粒包覆住在培養基中的正十六烷，把剩下的烷類有效移除。TN-4混合菌株所形成的結塊大多數都呈暗黃色，且顆粒都比較結實緊密，NTU-1所形成的菌團卻以乳白色爲主，與TN-4比較起來較爲鬆散，烷類的包覆效果也沒TN-4好。另外，從實驗中發現於培養基中加入己酸後會使細菌會變得更容易的靠攏聚集在一起。TN-4與NTU-1處理正十六烷時所呈現的生物降解能力與結塊極爲相似，證明NTU-1是主導生物降解與形成結塊的主要功臣。細菌結塊的能力能夠將烷類有效移除，因此微生物結塊能力之研究是不容忽視的。

Petroleum is one of the world’s major resources of energy. Nevertheless, continual exploitation of petroleum hydrocarbon has severely polluted our environment and threatened the well being of human life. The major purpose of this research was to investigate n-hexadecane biodegradability and bioflocculate formation performed by a mixed culture TN-4 and a pure culture Rhodococcus erythropolis NTU-1. Two key abiotic factors (1) n-hexadecane concentration and (2) initial acidity of culture medium, were altered to carry out the research work. It was discovered that the growth of TN-4 increased as the concentration of n-hexadecane rises even though the alkane consumption ability performed was fairly alike especially under high substrate concentration. However, both growth and biodegradability of NTU-1 was not affected for culture under different concentration of n-hexadecane. In addition, TN-4 and NTU-1 attained the best alkane removal efficiency when the initial acidity of culture medium was adjusted to pH 7.5. Both strains successfully removed almost 100% of n-hexadecane (up to 1470 ppm) after incubation for 66 hours. The bioremediation process was accompanied by formation of bacterial pellets (bioflocculate), with size ranging from 0.1 to 2 cm in diameter. This flocculation mechanism had provided high removal efficiency as most of the residual n-hexadecane was engulfed by the bacterial pellets and being consequently biodegraded. Aggregates formed by TN-4 are yellowish, round in shape and relatively firmer. Aggregates formed by NTU-1 are white in color and much incompact in comparison. Furthermore, it was also discovered that further addition of hexanoic acid into the culture could have possibly modified the surface properties of the cell because the flocs formed during incubation tended to attach to each other furing incubation. Besides that, due to the comparable results shown by these two strains, it was postulated that NTU-1 played a primary role of n-hexadecane degradation as well as bioflocculate formation throughout the process. Last but not least, development of bioflocculate was non trivial due to its importance in the enhancement of alkane mediation as well as easy removal of suspended solids in wastewater treatment.