Jemil Nawel, Ben Ayed Hanen, Hmidet Noomen, Nasri Moncef
Laboratoire de Génie Enzymatique et de Microbiologie, Ecole Nationale d'Ingénieurs de Sfax, Université de Sfax, B. P. 1173-3038, Sfax, Tunisia.
World J Microbiol Biotechnol. 2016 Nov;32(11):175. doi: 10.1007/s11274-016-2132-2. Epub 2016 Sep 15.
Six biosurfactant-producing bacteria were isolated from hydrocarbon contaminated soils in Sfax, Tunisia. Isolates were screened for biosurfactant production by different conventional methods including hemolytic activity, surface tension reduction, drop-collapsing and oil displacement tests. All these screening tests show that all the isolates behave differently. Among the isolated bacteria, DCS1 strain was selected for further studies based on its highest activities and it was identified as Bacillus methylotrophicus DCS1. This strain was found to be a potent producer of biosurfactant when cultivated in mineral-salts medium supplemented with diesel oil (2 %, v/v) as a sole carbon source. Physicochemical properties and stability of biosurfactants synthesized by B. methylotrophicus DCS1 were investigated. The produced biosurfactants DCS1, from Landy medium, possess high surface activity that could lower the surface tension of water to a value of 31 from 72 mN m(-1) and have a critical micelle concentration (CMC) of 100 mg L(-1). Compared with SDS and Tween 80, biosurfactants showed excellent emulsification activities against different hydrocarbon substrates and high solubilization efficiency towards diesel oil. Biosurfactants DCS1 showed good stability in a wide range of temperature, pH and salinity. These results suggested that biosurfactants produced by B. methylotrophicus DCS1 could be an alternative to chemically synthesized surfactants for use in bioremediation processes to enhance the solubility of hydrophobic compounds.
从突尼斯斯法克斯受碳氢化合物污染的土壤中分离出6株产生物表面活性剂的细菌。通过溶血活性、表面张力降低、液滴塌陷和油置换试验等不同常规方法对分离株进行生物表面活性剂生产筛选。所有这些筛选试验表明，所有分离株的表现各不相同。在分离出的细菌中，DCS1菌株因其最高活性被选作进一步研究对象，并被鉴定为甲基营养芽孢杆菌DCS1。当该菌株在补充了2%（v/v）柴油作为唯一碳源的矿物盐培养基中培养时，被发现是一种高效的生物表面活性剂生产者。对甲基营养芽孢杆菌DCS1合成的生物表面活性剂的理化性质和稳定性进行了研究。从兰迪培养基中产生的生物表面活性剂DCS1具有高表面活性，可将水的表面张力从72 mN m(-1) 降低到31 mN m(-1)，临界胶束浓度（CMC）为100 mg L(-1)。与十二烷基硫酸钠（SDS）和吐温80相比，生物表面活性剂对不同碳氢化合物底物表现出优异的乳化活性，对柴油具有高增溶效率。生物表面活性剂DCS1在广泛的温度、pH和盐度范围内表现出良好的稳定性。这些结果表明，甲基营养芽孢杆菌DCS1产生的生物表面活性剂可替代化学合成表面活性剂，用于生物修复过程中提高疏水性化合物的溶解度。
