Navon-Venezia S, Zosim Z, Gottlieb A, Legmann R, Carmeli S, Ron E Z, Rosenberg E
Department of Molecular Microbiology & Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.
Appl Environ Microbiol. 1995 Sep;61(9):3240-4. doi: 10.1128/aem.61.9.3240-3244.1995.
Acinetobacter radioresistens KA53, isolated by enrichment culture, was found to produce an extracellular, nondialyzable emulsifying agent (referred to as alasan) when grown on ethanol medium in a batch-fed reactor. The crude emulsifier was concentrated from the cell-free culture fluid by ammonium sulfate precipitation to yield 2.2 g of emulsifier per liter. Alasan stabilized a variety of oil-in-water emulsions, including n-alkanes with chain lengths of 10 or higher, alkyl aromatics, liquid paraffin, soybean and coconut oils, and crude oil. Alasan was 2.5 to 3.0 times more active after being heated at 100 degrees C under neutral or alkaline conditions. Emulsifying activity was observed over the entire pH range studied (pH 3.3 to 9.2), with a clear maximum at pH 5.0. Magnesium ions stimulated the activity both below (pH 3.3 to 4.5) and above (pH 5.5 to 9.3) the pH optimum. Alasan activity was higher in 20 mM citrate than in 20 mM acetate or Tris-HCl buffer. Preliminary chemical characterization of alasan indicated that it is a complex of an anionic, high-molecular-weight, alanine-containing heteropolysaccharide and protein.
通过富集培养分离得到的抗辐射不动杆菌KA53，发现在分批补料反应器中于乙醇培养基上生长时可产生一种胞外、不可透析的乳化剂（称为阿拉山菌素）。粗乳化剂通过硫酸铵沉淀从无细胞培养液中浓缩得到，每升培养液可得到2.2克乳化剂。阿拉山菌素可稳定多种水包油乳液，包括链长为10或更长的正构烷烃、烷基芳烃、液体石蜡、大豆油和椰子油以及原油。阿拉山菌素在中性或碱性条件下于100℃加热后活性提高2.5至3.0倍。在所研究的整个pH范围内（pH 3.3至9.2）均观察到乳化活性，在pH 5.0时活性明显最高。镁离子在低于（pH 3.3至4.5）和高于（pH 5.5至9.3）最适pH时均刺激活性。阿拉山菌素在20 mM柠檬酸盐中的活性高于在20 mM乙酸盐或Tris-HCl缓冲液中的活性。阿拉山菌素的初步化学表征表明它是一种由阴离子、高分子量、含丙氨酸的杂多糖和蛋白质组成的复合物。
