Vandermeer Krista D, Daugulis Andrew J
Department of Chemical Engineering, Queen's University, K7L 3N6 Kingston, Ontario, Canada.
Biodegradation. 2007 Apr;18(2):211-21. doi: 10.1007/s10532-006-9056-8. Epub 2006 Jun 7.
Biological treatment methods are effective at destroying polycyclic aromatic hydrocarbons (PAHs), and some of the highest rates of PAH degradation have been achieved using two-phase-partitioning bioreactors (TPPBs). TPPBs consist of a cell-containing aqueous phase and a biocompatible and immiscible organic phase that partitions toxic and/or recalcitrant substrates to the cells based on their metabolic demand and on maintaining the thermodynamic equilibrium of the system. In this study, the degradation of a 5-component mixture of high and low molecular weight PAHs by a defined microbial consortium of Sphingomonas aromaticivorans B0695 and Sphingomonas paucimobilis EPA505 in a TPPB was examined. The extremely low aqueous solubilities of the high molecular weight (HMW) PAHs significantly reduce their bioavailability to cells, not only in the environment, but in TPPBs as well. That is, in the two-phase system, the originally selected solvent, dodecane, was found to sequester the HMW PAHs from the cells in the aqueous phase due to the inherent high solubility of the hydrophobic compounds in this solvent. To circumvent this limitation, the initial PAH concentrations in dodecane were increased to sufficient levels in the aqueous phase to support degradation: LMW PAHs (naphthalene, phenanthrene) and fluoranthene were degraded completely in 8 h, while the HMW PAHs, pyrene and benzo[a]pyrene, were degraded by 64% and 11%, at rates of 42.9 mg l(-1) d(-1) and 7.5 mg l(-1) d(-1), respectively. Silicone oil has superior PAH partitioning abilities compared to dodecane for the HMW PAHs, and was used to improve the extent of degradation for the PAH mixture. Although silicone oil increased the bioavailability of the HMW PAHs and greater extents of biodegradation were observed, the rates of degradation were lower than that obtained in the TPPB employing dodecane.
生物处理方法在破坏多环芳烃（PAHs）方面很有效，使用两相分配生物反应器（TPPBs）已实现了一些最高的PAH降解率。TPPBs由含细胞的水相和生物相容且不混溶的有机相组成，该有机相根据细胞的代谢需求和维持系统的热力学平衡将有毒和/或难降解的底物分配给细胞。在本研究中，考察了鞘氨醇单胞菌B0695和少动鞘氨醇单胞菌EPA505组成的特定微生物群落，在TPPB中对高分子量和低分子量PAHs的五组分混合物的降解情况。高分子量（HMW）PAHs极低的水溶性显著降低了它们对细胞的生物可利用性，不仅在环境中如此，在TPPBs中也是如此。也就是说，在两相系统中，由于疏水性化合物在最初选择的溶剂十二烷中具有固有的高溶解度，发现它会从水相中的细胞中螯合HMW PAHs。为了克服这一限制，将十二烷中PAH的初始浓度提高到水相中足以支持降解的水平：低分子量PAHs（萘、菲）和荧蒽在8小时内完全降解，而高分子量PAHs芘和苯并[a]芘分别降解了64%和11%，降解速率分别为42.9 mg l(-1) d(-1)和7.5 mg l(-1) d(-1)。与十二烷相比，硅油对HMW PAHs具有更好的PAH分配能力，被用于提高PAH混合物的降解程度。尽管硅油提高了HMW PAHs的生物可利用性，并且观察到了更大程度的生物降解，但降解速率低于使用十二烷的TPPB中的降解速率。
