Bacterial Diversity of a Consortium Degrading High-Molecular-Weight Polycyclic Aromatic Hydrocarbons in a Two-Liquid Phase Biosystem

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. Although several PAH-degrading bacterial species have been isolated, it is not expected that a single isolate would exhibit the ability to degrade completely all PAHs. A consortium composed of different microorganisms can better achieve this. Two-liquid phase (TLP) culture systems have been developed to increase the bioavailability of poorly soluble substrates for uptake and biodegradation by microorganisms. By combining a silicone oil–water TLP system with a microbial consortium capable of degrading HMW PAHs, we previously developed a highly efficient PAH-degrading system. In this report, we characterized the bacterial diversity of the consortium with a combination of culture-dependent and culture-independent methods. Polymerase chain reaction (PCR) of part of the 16S ribosomal RNA gene (rDNA) sequences combined with denaturing gradient gel electrophoresis was used to monitor the bacterial population changes during PAH degradation of the consortium when pyrene, chrysene, and benzo[a]pyrene were provided together or separately in the TLP cultures. No substantial changes in bacterial profiles occurred during biodegradation of pyrene and chrysene in these cultures. However, the addition of the low-molecular-weight PAHs phenanthrene or naphthalene in the system favored one bacterial species related to Sphingobium yanoikuyae. Eleven bacterial strains were isolated from the consortium but, interestingly, only one—IAFILS9 affiliated to Novosphingobium pentaromativorans—was capable of growing on pyrene and chrysene as sole source of carbon. A 16S rDNA library was derived from the consortium to identify noncultured bacteria. Among 86 clones screened, 20 were affiliated to different bacterial species–genera. Only three strains were represented in the screened clones. Eighty-five percent of clones and strains were affiliated to Alphaproteobacteria and Betaproteobacteria; among them, several were affiliated to bacterial species known for their PAH degradation activities such as those belonging to the Sphingomonadaceae. Finally, three genes involved in the degradation of aromatic molecules were detected in the consortium and two in IAFILS9. This study provides information on the bacterial composition of a HWM PAH-degrading consortium and its dynamics in a TLP biosystem during PAH degradation.     

木质纤维素的微生物降解

木质纤维素广泛存在于自然界中,因结构复杂,其高效降解需要多种微生物的协同互作,由于参与木质纤维素降解的微生物种类繁多,其协同降解机理尚不完全明确。随着微生物分子生物学和组学技术的快速发展,将为微生物协同降解木质纤维素机制的研究提供新的方法和思路。笔者前期研究发现,细菌复合菌系在50℃下表现出强大的木质纤维素降解能力,菌系由可分离培养和暂时不可分离培养细菌组成,但是可分离培养细菌没有降解能力。通过宏基因组和宏转录组研究表明,与木质纤维素降解相关的某些基因表达量发生显著变化,通过组学方法有可能更加深入解释微生物协同降解木质纤维素的微生物学和酶学机理。文中从酶、纯培养菌株和复合菌群三个方面综述了木质纤维素微生物降解研究进展,着重介绍了组学技术在解析复合菌群作用机理方面的现状和应用前景,以期为探索微生物群落协同降解木质纤维素的机理提供借鉴。     

Microbial consortium bioaugmentation of a polycyclic aromatic hydrocarbons contaminated soil

In this study we evaluated the capacity of a defined microbial consortium (five bacteria: Mycobacterium fortuitum, Bacillus cereus, Microbacterium sp., Gordonia polyisoprenivorans, Microbacteriaceae bacterium, Naphthalene-utilizing bacterium; and a fungus identified as Fusarium oxysporum) isolated from a PAHs contaminated landfarm site to degrade and mineralize different concentrations (0, 250, 500 and 1000 mg kg(-1)) of anthracene, phenanthrene and pyrene in soil. PAHs degradation and mineralization was evaluated by gas chromatography and respirometry, respectively. The microbial consortium degraded on average, 99%, 99% and 96% of the different concentrations of anthracene, phenanthrene and pyrene in the soil, in 70 days, respectively. This consortium mineralized 78%, on average, of the different concentrations of the 3 PAHs in soil after 70 days. Contrarily, the autochthonous soil microbial population showed no substantial mineralization of the PAHs. Bacterial and fungal isolates from the consortium, when inoculated separately to the soil, were less effective in anthracene mineralization compared to the consortium. This signifies synergistic promotion of PAHs mineralization by mixtures of the monoculture isolates (the microbial consortium).     

表面活性剂影响微生物降解多环芳烃的研究进展

多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)的强疏水性是阻止其在土壤和水环境中微生物降解的主要因素.表面活性剂由于能够提高PAHs的表观溶解度而在PAHs的微生物降解中得到了广泛研究.截至目前,有关化学或生物表面活性剂促进PAHs的微生物降解已有大量报道,然而也有学者发现了表面...     

Enhanced Degradation of a Mixture of Polycyclic Aromatic Hydrocarbons by a Defined Microbial Consortium in a Two-Phase Partitioning Bioreactor

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.     

Enhanced biodegradation of phenol by a microbial consortium in a solid–liquid two phase partitioning bioreactor

Two phase partitioning bioreactors (TPPBs) operate by partitioning toxic substrates to or from an aqueous, cell-containing phase by means of second immiscible phase. Uptake of toxic substrates by the second phase effectively reduces their concentration within the aqueous phase to sub-inhibitory levels, and transfer of molecules between the phases to maintain equilibrium results in the continual feeding of substrate based on the metabolic demand of the microorganisms. Conventionally, a single pure species of microorganism, and a pure organic solvent, have been used in TPPBs. The present work has demonstrated the benefits of using a mixed microbial population for the degradation of phenol in a TPPB that uses solid polymer beads (comprised of ethylene vinyl acetate, or EVA) as the second phase. Polymer modification via an increase in vinyl acetate concentration was also shown to increase phenol uptake. Microbial consortia were isolated from three biological sources and, based on an evaluation of their kinetic performance, a superior consortium was chosen that offered improved degradation when compared to a pure strain of Pseudomonas putida ATCC 11172. The new microbial consortium used within a TPPB was capable of degrading high concentrations of phenol (2000mgl^–1), with decreased lag time (10h) and increased specific rate of phenol degradation (0.71g phenolg^–1cellh). Investigation of the four-member consortium showed that it consisted of two Pseudomonas sp., and two Acinetobacter sp., and tests conducted upon the individual isolates, as well as paired organisms, confirmed the synergistic benefit of their existence within the consortium. The enhanced effects of the use of a microbial consortium now offer improved degradation of phenol, and open the possibility of the degradation of multiple toxic substrates via a polymer-mediated TPPB system.     

复合菌系降解纤维素过程中微生物群落结构的变化

为明确高效纤维素降解复合菌系降解过程中微生物群落结构的变化规律及关键的降解功能菌,利用该复合菌系对滤纸和稻秆进行生物处理,通过底物降解、微生物生长量、发酵液pH的变化情况,选择不同降解时期复合菌系提取的总DNA进行细菌16S rRNA基因扩增子高通量测序。通过分解特性试验确定在接种后培养第12、72、168 h分别作为降解初期、高峰期、末期。该复合菌系分别主要由1个门、2个纲、2个目、7个科、11个属组成。随着降解的进行,短芽胞杆菌属Brevibacillus、喜热菌属Caloramator的相对丰度逐渐降低;梭菌属Clostridium、芽胞杆菌属Bacillus、地芽胞杆菌属Geobacillus、柯恩氏菌属Cohnella的相对丰度逐渐升高;解脲芽胞杆菌属Ureibacillus、泰氏菌属Tissierella、刺尾鱼菌属Epulopiscium在降解高峰期时相对丰度最高;各时期类芽胞杆菌属Paenibacillus、瘤胃球菌属Ruminococcus的相对丰度无明显变化。上述11个主要菌属均属于厚壁菌门,具有嗜热、耐热、适应广泛pH、降解纤维素或半纤维素的特性。好氧型细菌是降解初期的主要优势功能菌,到中后期厌氧型细菌逐渐增多,并逐步取代好氧型细菌成为降解纤维素的主要细菌。     

Characterization of 4-nonylphenol-degrading bacterial consortium obtained from a textile wastewater pretreatment plant

4-Nonylphenol (4-NP) isomers are toxic and recalcitrant compounds often resulting, together with short-chain ethoxylated nonylphenol (NPnEO, where n is the number of ethylene oxide units), from NPnEO biodegradation in conventional activated sludge plants. In this work, a microbial consortium, defined as Consortium A, capable of removing 100 mg/L of 4-NP with no accumulation of metabolites with aromatic moiety was isolated from textile wastewaters after enrichment with 4-NP. The consortium showed remarkable degradation activities toward several short-chain NPnEO congeners. Culture-dependent techniques were used to isolate from the consortium twenty-six strains assigned to seven different amplified ribosomal DNA restriction analysis groups. Two- and three-member cocultures were prepared with the strains showing highest 4-NP-degrading capabilities, but neither the single strains nor the cocultures were as efficient in 4-NP degradation as Consortium A. FISH was used to characterize the microbial composition of Consortium A: it evidenced a strong occurrence of Proteobacteria and, in particular, of Gammaproteobacteria along with a relevant stability of the culture. Therefore, the isolated consortium has the potential of being used in the development of a biotechnological process for the tertiary treatment of effluents of activated sludge plants fed with NPnEO-contaminated wastewaters.     

Characterization of a Polycyclic Aromatic Hydrocarbon-Degrading Microbial Consortium from a Petrochemical Sludge Landfarming Site

Anthracene, phenanthrene, and pyrene are polycyclic aromatic hydrocarbon (PAHs) that display both mutagenic and carcinogenic properties. They are recalcitrant to microbial degradation in soil and water due to their complex molecular structure and low solubility in water. This study presents the characterization of an efficient PAH (anthracene, phenanthrene, and pyrene)-degrading microbial consortium, isolated from a petrochemical sludge landfarming site. Soil samples collected at the landfarming area were used as inoculum in Warburg flasks containing soil spiked with 250 mg kg^-1 of anthracene. The soil sample with the highest production of CO₂-C in 176 days was used in liquid mineral medium for further enrichment of anthracene degraders. The microbial consortium degraded 48%, 67%, and 22% of the anthracene, phenanthrene, and pyrene in the mineral medium, respectively, after 30 days of incubation. Six bacteria, identified by 16S rRNA sequencing as Mycobacterium fortuitum, Bacillus cereus, Microbacterium sp., Gordonia polyisoprenivorans, two Microbacteriaceae bacteria, and a fungus identified as Fusarium oxysporum were isolated from the enrichment culture. The consortium and its monoculture isolates utilized a variety of hydrocarbons including PAHs (pyrene, anthracene, phenanthrene, and naftalene), monoaromatics hydrocarbons (benzene, ethylbenzene, toluene, and xylene), aliphatic hydrocarbons (1-decene, 1-octene, and hexane), hydrocarbon mixtures (gasoline and diesel oil), intermediary metabolites of PAHs degradation (catechol, gentisic acid, salicylic acid, and dihydroxybenzoic acid) and ethanol for growth. Biosurfactant production by the isolates was assessed by an emulsification index and reduction of the surface tension in the mineral medium. Significant emulsification was observed with the isolates, indicating production of high-molecular-weigh surfactants. The high PAH degradation rates, the wide spectrum of hydrocarbons utilization, and emulsification capacities of the microbial consortium and its member microbes indicate that they can be used for biotreatment and bioaugumentation of soils contaminated with PAHs.     

细菌降解萘、菲的代谢途径及相关基因的研究进展

多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)是一类在环境中广泛存在的具有毒性的污染物,微生物降解是其在自然界中降解的主要途径,因而尤为重要。随着研究的深入,关于微生物降解PAHs的分子降解机制、途径等的认识逐渐积累。以下对细菌降解萘、菲的研究进展进行了概述,介绍了萘的水杨酸降解途径,菲的水杨酸、邻苯二甲酸及其他降解途径,同时也包括降解过程中涉及的降解基因簇,如nah-like、phn、phd、nid和nag等以及细菌在PAHs胁迫条件下其他相关基因的表达与调节等方面的最新进展。这些进展可为降解菌株的分子及遗传机制研究提供理论依据,将促进通过基因工程优化降解菌、更有效地检测PAHs环境污染及实现PAHs污染的生物修复。     

Degradation of Di- Through Hepta-Chlorobiphenyls in Clophen Oil Using Microorganisms Isolated from Long Term PCBs Contaminated Soil

Present work describes microbial degradation of selected polychlorinated biphenyls (PCBs) congeners in Clophen oil which is used as transformer oil and contains high concentration of PCBs. Indigenous PCBs degrading bacteria were isolated from Clophen oil contaminated soil using enrichment culture technique. A 15 days study was carried out to assess the biodegradation potential of two bacterial cultures and their consortium for Clophen oil with a final PCBs concentration of 100 mg kg⁻¹. The degradation capability of the individual bacterium and the consortium towards the varying range of PCBs congeners (di- through hepta-chlorobiphenyls) was determined using GCMS. Also, dehydrogenase enzyme was estimated to assess the microbial activity. Maximum degradation was observed in treatment containing consortium that resulted in up to 97 % degradation of PCB-44 which is a tetra chlorinated biphenyl whereas, hexa chlorinated biphenyl congener (PCB-153) was degraded up to 90 % by the consortium. This indicates that the degradation capability of microbial consortium was significantly higher than that of individual cultures. Furthermore, the results suggest that for degradation of lower as well as higher chlorinated PCB congeners; a microbial consortium is required rather than individual cultures.     

A sequential aerobic/microaerophilic decolorization of sulfonated mono azo dye Golden Yellow HER by microbial consortium GG-BL

This study is a part of efforts to develop new batch method with the help of prepared consortium GG-BL using two microbial cultures viz. Galactomyces geotrichum MTCC 1360 and Brevibacillus laterosporus NCIM 2298, varying oxidation conditions for the bio-treatment processes to produce reusable water by decolorization of Golden Yellow HER (GYHER) to less toxic metabolites. Consortium was found to be much faster for decolorization and degradation of GYHER as compared to the individual strains. The intensive metabolic activity of these strains led to 100% decolorization of GYHER (50 mg l⁻¹) within 24 h with significant reduction in chemical oxygen demand (84%) and total organic carbon (63%). The presence of veratryl alcohol oxidase, NADH-DCIP reductase and induction in laccase, tyrosinase, azo reductase and riboflavin reductase during decolorization suggests their role in decolorization process. Substrate staining of nondenaturing polyacrylamide electrophoresis gel (PAGE) also confirms induction of oxidative enzymes during GYHER degradation. The degradation of the GYHER into different metabolites by individual organism and in consortium was confirmed using High Performance Thin Layer Chromatography (HPTLC), High Performance Liquid Chromatography (HPLC), Fourier Transform Infra Red Spectroscopy (FTIR), Gas Chromatography Mass Spectroscopy (GC–MS) analysis. Phytotoxicity studies revealed nontoxic nature of the metabolites of GYHER.     

A Perspective on the Toxicity of Petrogenic PAHs to Developing Fish Embryos Related to Environmental Chemistry

Numerous studies demonstrate polynuclear aromatic hydrocarbons (PAHs) dissolved from weathered crude oil adversely affect fish embryos at 0.5 to 23 μg/l. This conclusion has been challenged by studies that claim (1) much lower toxicity of weathered aqueous PAHs; (2) direct contact with dispersed oil droplets plays a significant role or is required for toxicity; (3) that uncontrolled factors (oxygen, ammonia, and sulfides) contribute substantively to toxicity; (4) polar compounds produced by microbial metabolism are the major cause of observed toxicity; and (5) that based on equilibrium models and toxic potential, water contaminated with weathered oil cannot be more toxic per unit mass than effluent contaminated with fresh oil. In contrast, several studies demonstrate high toxicity of weathered oil; shifts in PAH composition were consistent with dissolution (not particle ablation), embryos accumulated dissolved PAHs at low concentrations and were damaged, and assumed confounding factors were inconsequential. Consistent with previous empirical observations of mortality and weathering, temporal shifts in PAH composition (oil weathering) indicate that PAHs dissolved in water should (and do) become more toxic per unit mass with weathering because high molecular weight PAHs are more persistent and toxic than the more abundant low molecular weight PAHs in whole oil.     

Bioremediation of high molecular weight polycyclic aromatic hydrocarbons: a review of the microbial degradation of benzo[a]pyrene

Over the past 30 years, research on the microbial degradation of polycyclic aromatic hydrocarbons (PAHs) has resulted in the isolation of numerous genera of bacteria, fungi and algae capable of degrading low molecular weight PAHs (compounds containing three or less fused benzene rings). High molecular weight PAHs (compounds containing four or more fused benzene rings) are generally recalcitrant to microbial attack, although some fungi and algae are capable of transforming these compounds. Until recently, only a few genera of bacteria have been isolated with the ability to utilise four-ring PAHs as sole carbon and energy sources while cometabolism of five-ring compounds has been reported. The focuss of this review is on the high molecular weight PAH benzo[a]pyrene (BaP). There is concern about the presence of BaP in the environment because of its carcinogenicity, teratogenicity and toxicity. BaP has been observed to accumulate in marine organisms and plants which could indirectly cause human exposure through food consumption. This review provides an outline of the occurrence of BaP in the environment and the ability of bacteria, fungi and algae to degrade the compound, including pathways for BaP degradation by these organisms. In addition, approaches for improving microbial degradation of BaP are discussed.     

多环芳烃微生物降解基因的研究进展

多环芳烃(PAHs)是环境中普遍存在的一类有机污染物,微生物的降解是PAHs去除的主要途径。近年来,有关PAHs微生物降解途径和代谢产物的研究已有很多报道。小分子PAHs一般可以直接被微生物降解,而大分子PAHs则需要微生物以共代谢的方式降解。在过去20年中,微生物降解PAHs的基因相继被发现,各种基因在调控PAHs降解过程中的功能也越来越清晰。本文概述了PAHs微生物降解基因方面的研究进展,详细介绍了微生物对萘、菲的降解基因,最后对PAHs微生物降解基因的应用前景进行了展望。     

Recent developments in microbial biotransformation and biodegradation of dioxins

Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), commonly known as dioxins (PCDD/Fs), are toxic environmental pollutants formed from various sources. Elimination of these pollutants from the environment is a difficult task due to their persistent and ubiquitous nature. Removal of dioxins by biological degradation (biodegradation) is considered a feasible method as an alternative to other expensive physicochemical approaches. Biodegradation of dioxins has been extensively studied in several microorganisms, and details concerning biodiversity, biodegradation, biochemistry and molecular biology of this process have accumulated during the last three decades. There are several microbial mechanisms responsible for biodegradation of dioxins, including oxidative degradation by dioxygenase-containing aerobic bacteria, bacterial and fungal cytochrome P-450, fungal lignolytic enzymes, reductive dechlorination by anaerobic bacteria, and direct ether ring cleavage by fungi containing etherase-like enzymes. Many attempts have been made to bioremediate PCDD/Fs using this basic knowledge of microbial dioxin degradation. This review emphasizes the present knowledge and recent advancements in the microbial biotransformation, biodegradation and bioremediation of dioxins.     

Optimization of high-molecular-weight polycyclic aromatic hydrocarbons' degradation in a two-liquid-phase bioreactor

A microbial consortium degrading the high-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs) pyrene, chrysene, benzo[a]pyrene and perylene in a two-liquid-phase reactor was studied. The highest PAH-degrading activity was observed with silicone oil as the water-immiscible phase; 2,2,4,4,6,8, 8-heptamethylnonane, paraffin oil, hexadecane and corn oil were much less, or not efficient in improving PAH degradation by the consortium. Addition of surfactants (Triton X-100, Witconol SN70, Brij 35 and rhamnolipids) or Inipol EAP22 did not promote PAH biodegradation. Rhamnolipids had an inhibitory effect. Addition of salicylate, benzoate, 1-hydroxy-2-naphtoic acid or catechol did not increase the PAH-degrading activity of the consortium, but the addition of low-molecular-weight (LMW) PAHs such as naphthalene and phenanthrene did. In these conditions, the degradation rates were 27 mg l-1 d-1 for pyrene, 8.9 mg l-1 d-1 for chrysene, 1.8 mg l-1 d-1 for benzo[a]pyrene and 0.37 mg l-1 d-1 for perylene. Micro-organisms from the interface were slightly more effective in degrading PAHs than those from the aqueous phase.     

Two-liquid-phase slurry bioreactors to enhance the degradation of high-molecular-weight polycyclic aromatic hydrocarbons in soil

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. The addition of a water-immiscible, nonbiodegradable, and biocompatible liquid, silicone oil, to a soil slurry was studied to promote the desorption of PAHs from soil and to increase their bioavailability. First, the transfer into silicone oil of phenanthrene, pyrene, chrysene, and benzo[a]pyrene added to a sterilized soil (sandy soil with 0.65% total volatile solids) was measured for 4 days in three two-liquid-phase (TLP) slurry systems each containing 30% (w/v) soil but different volumes of silicone oil (2.5%, 7.5%, and 15% [v/v]). Except for chrysene, a high percentage of these PAHs was transferred from soil to silicone oil in the TLP slurry system containing 15% silicone oil. Rapid PAH transfer occurred during the first 8 h, probably resulting from the extraction of nonsolubilized and of poorly sorbed PAHs. This was followed by a period in which a slower but constant transfer occurred, suggesting extraction of more tightly bound PAHs. Second, a HMW PAH-degrading consortium was enriched in a TLP slurry system with a microbial population isolated from a creosote-contaminated soil. This consortium was then added to three other TLP slurry systems each containing 30% (w/v) sterilized soil that had been artificially contaminated with pyrene, chrysene, and benzo[a]pyrene, but different volumes of silicone oil (10%, 20%, and 30% [v/v]). The resulting TLP slurry bioreactors were much more efficient than the control slurry bioreactor containing the same contaminated soil but no oil phase. In the TLP slurry bioreactor containing 30% silicone oil, the rate of pyrene degradation was 19 mg L(-)(1) day(-)(1) and no pyrene was detected after 4 days. The degradation rates of chrysene and benzo[a]pyrene in the 30% TLP slurry bioreactor were, respectively, 3.5 and 0.94 mg L(-)(1) day(-)(1). Low degradation of pyrene and no significant degradation of chrysene and benzo[a]pyrene occurred in the slurry bioreactor. This is the first report in which a TLP system was combined with a slurry system to improve the biodegradation of PAHs in soil.     

Biodegradation of Oil Tank Bottom Sludge using Microbial Consortia

We present a rationale for the selection of a microbial consortia specifically adapted to degrade toxic components of oil refinery tank bottom sludge (OTBS). Sources such as polluted soils, petrochemical waste, sludge from refinery-wastewater plants, and others were used to obtain a collection of eight microorganisms, which were individually tested and characterized to analyze their degradative capabilities on different hydrocarbon families. After initial experiments using mixtures of these strains, we developed a consortium consisting of four microorganisms (three bacteria and one yeast) selected in the basis of their cometabolic effects, emulsification properties, colonization of oil components, and degradative capabilities. Although the specific contribution each of the former parameters makes is not clearly understood, the activity of the four-member consortium had a strong impact not only on linear alkane degradation (100%), but also on the degradation of cycloalkanes (85%), branched alkanes (44%), and aromatic and sulphur–aromatic compounds (31–55%). The effectiveness of this consortium was significantly superior to that obtained by individual strains, commercial inocula or an undefined mixture of culturable and non-culturable microorganisms obtained from OTBS-polluted soil. However, results were similar when another consortium of four microorganisms, previously isolated in the same OTBS-polluted soil, was assayed.     

Improved Enrichment and Isolation of Polycyclic Aromatic Hydrocarbons (PAH)-Degrading Microorganisms in Soil Using Anthracene as a Model PAH

Lack of attention to soil and microbial characteristics that influence PAHs degradation has been a leading cause of failures in isolation of efficient PAH degraders and bioaugumentation processes with microbial consortia. This study compared the classic method of isolation of PAHs-degraders with a modified method employing a pre-enrichment respirometric analysis. The modified enrichment of PAH degrading microorganisms using in vitro microcosm resulted to reduced enrichment period and more efficient PAH-degrading microbial consortia. Results indicate that natural soils with strong heterotrophic microbial activity determined through pre-enrichment analysis, are better suited for the isolation of efficient PAH degrading microorganisms with significant reduction of the enrichment period.