Desai Anuradha M, Autenrieth Robin L, Dimitriou-Christidis Petros, McDonald Thomas J
Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
Biodegradation. 2008 Apr;19(2):223-33. doi: 10.1007/s10532-007-9129-3. Epub 2007 May 30.
Many contaminated sites commonly have complex mixtures of polycyclic aromatic hydrocarbons (PAHs) whose individual microbial biodegradation may be altered in mixtures. Biodegradation kinetics for fluorene, naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene were evaluated in sole substrate, binary and ternary systems using Sphingomonas paucimobilis EPA505. The first order rate constants for fluorene, naphthalene, 1,5-dimethylnaphthalene, and 1-methylfluorene were comparable; yet Monod parameters were significantly different for the tested PAHs. S. paucimobilis completely degraded all the components in binary and ternary mixtures; however, the initial degradation rates of individual components decreased in the presence of competitive PAHs. Results from the mixture experiments indicate competitive interactions, demonstrated mathematically. The generated model appropriately predicted the biodegradation kinetics in mixtures using parameter estimates from the sole substrate experiments, validating the hypothesis of a common rate-determining step. Biodegradation kinetics in mixtures were affected by the affinity coefficients of the co-occurring PAHs and mixture composition. Experiments with equal concentrations of substrates demonstrated the effect of concentration on competitive inhibition. Ternary experiments with naphthalene, 1,5-dimethylnaphthalene and 1-methylfluorene revealed delayed degradation, where depletion of naphthalene and 1,5-dimethylnapthalene occurred rapidly only after the complete removal of 1-methylfluorene. The substrate interactions observed in mixtures require a multisubstrate model to account for simultaneous degradation of substrates. PAH contaminated sites are far more complex than even ternary mixtures; however these studies clearly demonstrate the effect that interactions can have on individual chemical kinetics. Consequently, predicting natural or enhanced degradation of PAHs cannot be based on single compound kinetics as this assumption would likely overestimate the rate of disappearance.
许多受污染场地通常含有多环芳烃（PAHs）的复杂混合物，其单个微生物的生物降解在混合物中可能会发生改变。使用少动鞘氨醇单胞菌EPA505在单一底物、二元和三元体系中评估了芴、萘、1,5 - 二甲基萘和1 - 甲基芴的生物降解动力学。芴、萘、1,5 - 二甲基萘和1 - 甲基芴的一级速率常数相当；然而，测试的多环芳烃的莫诺德参数有显著差异。少动鞘氨醇单胞菌完全降解了二元和三元混合物中的所有成分；然而，在存在竞争性多环芳烃的情况下，单个成分的初始降解速率降低。混合物实验结果表明存在竞争性相互作用，通过数学方法得到了证明。生成的模型使用来自单一底物实验的参数估计值，恰当地预测了混合物中的生物降解动力学，验证了存在共同速率决定步骤的假设。混合物中的生物降解动力学受共存多环芳烃的亲和系数和混合物组成的影响。等浓度底物的实验证明了浓度对竞争性抑制的影响。萘、1,5 - 二甲基萘和1 - 甲基芴的三元实验显示降解延迟，其中萘和1,5 - 二甲基萘只有在1 - 甲基芴完全去除后才迅速消耗。在混合物中观察到的底物相互作用需要一个多底物模型来解释底物的同时降解。多环芳烃污染场地比三元混合物甚至还要复杂得多；然而这些研究清楚地证明了相互作用对单个化学动力学可能产生的影响。因此，预测多环芳烃的自然或强化降解不能基于单一化合物的动力学，因为这种假设可能会高估消失速率。
