Barzegar Gelavizh, Jorfi Sahand, Sanaei Daryoush, Rezaei Mina, Jokar Rosa, Sharifan Hamidreza, Jafari Khadijeh, Biswas Jayanta Kumar
Department of Environmental Health Engineering, Behbahan Faculty of Medical Sciences, Behbahan, Iran.
Department of Environmental Health Engineering, School of Public Health and Environmental Technologies Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Sci Rep. 2025 Jul 1;15(1):20673. doi: 10.1038/s41598-025-06954-2.
A biosurfactant-producing isolate, Bacillus subtilis AHV-KH11, was used for the biodegradation of diesel-contaminated saline soils. In addition to naturally occurring diesel contamination, the collected soil samples were artificially contaminated with diesel oil at concentrations ranging from 1000 to 5000 mg kg of soil. The operational parameters investigated in our experiment were the initial seed volume (5-20 mL), soil moisture content (100-300%), external surfactants (rhamnolipid and Tween 80), and salinity levels (0.5-2%). The results indicated that diesel biodegradation was optimized at an initial seed volume of 10 mL, while further increases up to 20 mL provided no additional benefit. This suggests that diesel biodegradation can be effectively initiated with a relatively modest bacterial inoculum. This study demonstrates how the remediation process enhances the salinity tolerance of Bacillus subtilis AHV-KH11, achieving effective remediation at 1.5% salinity without an external surfactant and enhanced performance at 8% salinity when exogenous rhamnolipid is added. The addition of rhamnolipid as an external biosurfactant increased the diesel biodegradation rate. In addition to accelerating diesel degradation, rhamnolipid significantly improved soil health, as demonstrated by toxicity assays using Eisenia fetida, the mortality rate dropped from 88% in untreated diesel-contaminated soil to 41% in bioremediated soil after 14 days. Furthermore, the salt tolerance of Bacillus subtilis AHV-KH11 can be enhanced, highlighting its potential as an efficient diesel decomposer and biosurfactant producer in pure or mixed cultures for the bioremediation of diesel-contaminated saline soils.
一株产生物表面活性剂的分离菌株枯草芽孢杆菌AHV-KH11被用于柴油污染盐渍土的生物降解。除了自然存在的柴油污染外，采集的土壤样本还用柴油进行了人工污染，柴油浓度范围为每千克土壤1000至5000毫克。我们实验中研究的操作参数包括初始种子体积（5 - 20毫升）、土壤含水量（100 - 300%）、外部表面活性剂（鼠李糖脂和吐温80）以及盐度水平（0.5 - 2%）。结果表明，柴油生物降解在初始种子体积为10毫升时达到最佳，而进一步增加至20毫升并无额外益处。这表明用相对适量的细菌接种物就能有效启动柴油生物降解。本研究展示了修复过程如何提高枯草芽孢杆菌AHV-KH11的耐盐性，在不添加外部表面活性剂的情况下，在盐度为1.5%时实现有效修复，添加外源鼠李糖脂后在盐度为8%时性能增强。添加鼠李糖脂作为外部生物表面活性剂提高了柴油生物降解率。除了加速柴油降解外，鼠李糖脂还显著改善了土壤健康状况，如通过使用赤子爱胜蚓进行的毒性试验所示，14天后，死亡率从未经处理的柴油污染土壤中的88%降至生物修复土壤中的41%。此外，枯草芽孢杆菌AHV-KH11的耐盐性可以得到增强，突出了其在纯培养或混合培养中作为高效柴油分解菌和生物表面活性剂生产者用于柴油污染盐渍土生物修复的潜力。
