Department of Civil Engineering, McGill University, Montreal, Quebec H3A 0C3, Canada.
Department of Civil Engineering, McGill University, Montreal, Quebec H3A 0C3, Canada.
Sci Total Environ. 2021 Jul 15;778:145441. doi: 10.1016/j.scitotenv.2021.145441. Epub 2021 Jan 28.
Surfactants are used to enhance the bioavailability of recalcitrant residual petroleum contamination during bioremediation. However, surfactants in some cases inhibit biodegradation, which is often attributed to their toxicity. Herein, we show that a rhamnolipid biosurfactant likely served as a carbon source and exhibited physiological inhibition on petroleum biodegradation. The addition of biosurfactants in mixed, batch, slurry bioreactors with soils from a petroleum-contaminated site led to a dose-dependent shift in the microbial community with a decrease in diversity and increase in population size and delayed biodegradation. Microbial community analysis indicated the enrichment of Alphaproteobacteria affiliated taxa such as Sphingomonadaceae in systems amended with biosurfactant. The diversity was significantly lower in systems with higher doses of biosurfactants compared to systems without biosurfactant. Droplet Digital PCR indicated a 30-90 fold increase in 16S rRNA copy numbers in systems with higher doses of biosurfactant than control systems without surfactant and nutrients, whereas the nutrient amendment alone led to a two-fold increase in population size. Total petroleum hydrocarbon analysis showed that the biodegradation extent was negatively impacted by rhamnolipid at the highest dose compared to lower doses (23% vs. 40%) or without the biosurfactant. Indigenous isolates cultivated from the oil-amended soil exhibited growth on rhamnolipid as a sole carbon source. A novel insight gained is how dose-dependent responses of microbial communities to biosurfactants alter the biodegradation time profile of hydrocarbons. The study highlights the significance of microbial assessment prior to surfactant-mediated bioremediation practices.
表面活性剂被用于提高生物修复过程中难生物降解的残余石油污染的生物利用度。然而，在某些情况下，表面活性剂会抑制生物降解，这通常归因于它们的毒性。本文中，我们表明，鼠李糖脂生物表面活性剂可能充当碳源，并对石油生物降解表现出生理抑制作用。在受石油污染场地的土壤中进行的混合批次、泥浆生物反应器中添加生物表面活性剂会导致微生物群落的剂量依赖性变化，表现为多样性降低、种群大小增加和生物降解延迟。微生物群落分析表明，在添加生物表面活性剂的系统中，富集了与鞘脂单胞菌科相关的α变形菌属分类群。与不含生物表面活性剂的系统相比，含有较高剂量生物表面活性剂的系统中的多样性显著降低。液滴数字 PCR 表明，在含有较高剂量生物表面活性剂的系统中，16S rRNA 拷贝数比不含表面活性剂和营养物的对照系统增加了 30-90 倍，而仅营养物的添加就使种群大小增加了两倍。总石油烃分析表明，与较低剂量（23%比 40%）或不含生物表面活性剂相比，鼠李糖脂在最高剂量下对生物降解程度的负面影响更大。从油添加土壤中培养的土著分离物在鼠李糖脂作为唯一碳源时表现出生长。本文获得的一个新认识是，微生物群落对生物表面活性剂的剂量依赖性反应如何改变烃类的生物降解时间曲线。该研究强调了在进行表面活性剂介导的生物修复实践之前进行微生物评估的重要性。
