嗜酸嗜熱細菌之分離及其酯解酵素粗酵素液之性質研究

Abstract

從酸性的溫泉(約pH3、55℃)附近分離出數種細菌。依細菌的特性，其中一種分類為 Bacillus acidocaldarius，可生長於pH 3~4及45~65℃的培養條件下，生長最適pH及溫度分別是pH4及55℃。以p-nitrophenyl ester為受質，可於培養細菌的上清液中偵測到酯解酵素(esterase)的活性。橄欖油的添加雖然可促進細菌生長，但是對於酯解酵素的分泌似乎沒有明顯的影響。此酯解酵素作用之最適pH值及溫度分別為中性(pH7)及75℃。此酯解酵素可分解長碳鏈的酯質受質(pNPC12~pNPC16)，亦具有相當之熱穩定性，於75℃之半生期為30分鐘，而以95℃處理3小時後仍保留有18%%的活性。也測試了一些鹽類、清潔劑及金屬螯合劑EDTA對此酵素的影響，尚未找到可以促進該酯解酵素活性的離子；然而，清潔劑及某些離子則對酵素活性具有抑制的作用；另外，EDTA的添加不對酵素活性有所抑制。

Several moderate themlophilic bacterial strains were isolated from hot acid spring about pH 3 and 55℃ by enrichment methods. One of those was identified as Bacillus acidocaldarius. This strain grew undera narrow pH (pH 3~4) and moderate high temperature (45~65℃) condition and was optimal at pH 4 and55℃. A thermostable esterase activity was detected in the culture medium supernatant when assayed using the p-nitrophenyl ester. Adding olive oil to culture medium promoted bacterial growth, but had no effects on the esterase activity. The pH and temperature optima for the esterase activity were pH 7 and 75℃, respectively. This crude esterase activity was found capable of hydrolyzing long-chain fatty acid esters (pNPC 12 to pNPC 16) and exhibited thermal stability. It showed a half-life of 30 min at 75℃, and after 3 h incubation at 95 ℃, 18 % of the activity still remained. The effects of several kinds of salts, detergent, and chelating agent, EDT A were also examined. No ions used could promote the esterase activity, however, some detergents and ions had inhibitory effects on the enzyme, and EDTA had no inhibitory effect on it.