Biodiesel is a mixture of fatty acid methyl esters (FAME) from either vegetable oils or animal fats. Although biodiesel biodegrades faster than diesel fuel, the impacts of this biofuel in environment throughout its biodegradation process should be investigated. For this reason, the objective of the present study was to evaluate the microbial activity, the phytotoxicity, and the formation of metabolites during biodegradation of the contaminated soil with biodiesel. Microbial activity was evaluated using culture-dependent methods in soil samples artificially contaminated with biodiesel—followed by pH adjustments. The formation of metabolites during biodegradation was identified using gas chromatography coupled with mass spectrometry (GC/MS). Respirometric method was also applied to evaluate total microbial activity. Seeds of Cucumis sativus were sown in soil samples before and after biodegradation to expand our knowledge on the impacts of such metabolites in a eukaryotic test-organism. Culture-dependent assays successfully allowed the quantification of microorganisms during biodegradation. According to CO₂ production, biodiesel initially acted as a biostimulation agent increasing microbial activity. Indigenous microbiota degraded biodiesel into smaller compounds such as pentane, free fatty acids, and methanol. Soil pH significantly dropped from 5.4 to 3.0 after 120 days of biodegradation as a result of high concentration of free fatty acids. These free fatty acids inhibited further microbial growth after biodegradation. It was proposed that correcting soil acidity during biodegradation would be enough to sustain microbial growth. However, pH decrease was just one of the factors that inhibited microbial growth and plant root development. It was proposed that biodegradation yielded toxic metabolites such as methanol. These metabolites contributed to impair the root elongation due to alcohol-specific properties to solubilize a wide variety of lipids within the seed. Therefore, the present study draws attention to metabolites from biodegradation of biodiesel and their potentially harmful environmental impacts.Biodegradation of biodiesel changes soil pH, as it generates metabolites that are phytotoxic, and reduces microbial counts (CFU g⁻¹ dry soil).

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大豆生物柴油的生物降解在土壤中产生有毒代谢产物

生物柴油是植物油或动物脂肪中的脂肪酸甲酯（FAME）的混合物。尽管生物柴油的生物降解速度比柴油燃料快，但应研究这种生物燃料在其整个生物降解过程中对环境的影响。因此，本研究的目的是评估生物柴油对受污染土壤的生物降解过程中的微生物活性，植物毒性和代谢产物的形成。使用依赖于培养的方法，在被生物柴油人工污染的土壤样品中评估微生物活性，然后进行pH调节。使用气相色谱-质谱联用技术（GC / MS）可以确定生物降解过程中代谢产物的形成。呼吸测定法也用于评估总微生物活性。的种子在生物降解之前和之后，在土壤样品中播种了黄瓜（Cucumis sativus），以扩大我们对此类代谢产物在真核生物中的影响的认识。依赖培养物的测定法成功地实现了生物降解过程中微生物的定量分析。根据CO ₂在生产过程中，生物柴油最初起着增加微生物活性的生物刺激剂的作用。土著微生物群将生物柴油降解为较小的化合物，例如戊烷，游离脂肪酸和甲醇。经过120天的生物降解后，由于高浓度的游离脂肪酸，土壤的pH值从5.4显着下降至3.0。这些游离脂肪酸在生物降解后抑制了进一步的微生物生长。有人提出，在生物降解过程中校正土壤酸度足以维持微生物的生长。但是，pH降低只是抑制微生物生长和植物根系发育的因素之一。有人提出生物降解会产生有毒的代谢产物，例如甲醇。这些代谢物由于醇特有的特性而导致根伸长延长，从而溶解了种子中的多种脂质。因此，本研究引起了人们对生物柴油的生物降解及其潜在有害环境影响的关注。^-1干燥土壤）。