Effectiveness of surfactants in the microbial degradation of oil

Nonionic surfactants increase the rate of selective hydrocarbon utilization by Acinetobacter SL1. Within an homologus series of nonionic surfactants, growth on and utilization of a model oil by Acinetobacter SL1 is dependent upon the surfactant hydrophile‐lipophile balance (HLB). Biological effectiveness of the surfactants apparently is related to the degree of micelle formation by the surfactant in the aqueous phase. A simple algebraic expression describing the response of Acinetobacter SL1 to surfactant concentration gives a measure of the biological effectiveness of an individual surfactant. A cationic and an anionic surfactant inhibited the growth of Acinetobacter SL1 and Pseudomonas SL6 on hydrocarbon substrates. These results are discussed in relation to the selection of suitable detergents for increasing the effective biodegradation of pollutant oil in aquatic habitats.     

The effect of nutrient application and aeration on oil degradation in soil

Oil degradation was determined in oil-polluted (1 or 2 ml of light Nigerian crude/20 g soil, equivalent to 5 and 10% pollution) soils treated with (NH₄)₂SO₄ and with nutrient elements with and without enhanced aeration. There was no significant difference in oil degradation in soils with and without enhanced aeration, nor in soils treated with and without (NH₄)₂SO₄ and/or nutrients after 4 weeks incubation. After 12 weeks, oil degradation was significantly higher (p = 0·05) in the (NH₄)₂SO₄ and nutrient treated soils in comparison to the untreated soils, and in soils with enhanced aeration in comparison to the undisturbed soil, at the 5% oil pollution level.Warburg respirometer studies showed more oxygen consumption (significant at p = 0·05) in the polluted soils compared with the unpolluted soils. In oil-polluted soils oxygen consumption was depressed significantly (p = 0·05) by the addition of (NH₄)₂SO₄, but was enhanced significantly (p = 0·05) by the addition of (NH₄)₂SO₄ and nutrient elements. The respiratory quotient (RQ) was reduced from 0·81 in unpolluted soils to 0·62 in oil-polluted soils.     

Intensification of microbial degradation of crude oil and oil products in the presence of perfluorodecalin

The possibility of using perfluorinated organic compounds for growing microorganisms and degrading xenobiotics has been demonstrated for the first time with perfluorodecalin (PFD), a gas-transporting component of the blood substitute Perftoran. In particular, this is promising for intensifying microbial degradation of oil and oil products and production of biodegrader biomass in synthetic mineral media. Addition of PFD to a mineral medium with crude oil and masut increased 4.5-10.2 times maximum concentrations and growth rates of all bacterial strains under study (Pseudomonas, Rhodococcus, and Bacillus genera). The degree of oil product consumption was increased 8.7-12.7 times.     

The prospects of using bacteria of the genus Rhodococcus and microbial surfactants for the degradation of oil pollutants

The possibility of accelerating oil degradation by an enrichment culture of oil-oxidizing microorganisms in the presence of bacteria of the genus Rhodococcus and microbial surfactants was studied. It was shown that the degree of consumption of crude oil (2% v/v) after 192 h of enrichment culture growth reached 84%. Inoculation of the active hydrocarbon-oxidizing strain Rhodococcus erythropolis EK-1 and exogenous surfactants produced by Pseudomonas sp. PS-27 increased this degree to 90% and 93-94%, respectively. On the grounds of these results, efficient methods of purification of the environment from oil pollutants can be developed.     

The prospects of using bacteria of the genus Rhodococcus and microbial surfactants for the degradation of oil pollutants

The possibility of accelerating oil degradation by an enrichment culture of oil-oxidizing microorganisms in the presence of bacteria of the genus Rhodococcus and microbial surfactants was studied. It was shown that the degree of consumption of crude oil (2vol %) after 192 h of enrichment culture growth reached 84%. Inoculation of the active hydrocarbon-oxidizing strain Rhodococcus erythropolis EK-1 and exogenous surfactants produced by Pseudomonas sp. PS-27 increased this degree to 90 and 93–94%, respectively. On the grounds of these results, efficient methods of purification of the environment from oil pollutants can be developed.     

Molecular biologic techniques applied to the microbial prospecting of oil and gas in the Ban 876 gas and oil field in China

Currently, molecular biologic techniques achieve a great development in studies of soil samples. The objective of this research is to improve methods for microbial prospecting of oil and gas by applying culture-independent techniques to soil sampled from above a known oil and gas field. Firstly, the community structure of soil bacteria above the Ban 876 Gas and Oil Field was analyzed based on 16S rRNA gene clone libraries. The soil bacteria communities were consistently different along the depth; however, Chloroflexi and Gemmatimonadetes were predominant and methanotrophs were minor in both bacteria libraries (DGS1 and DGS2). Secondly, the numbers of methane-oxidizing bacteria, quantified using a culture-dependent procedure and culture-independent group-specific real-time PCR (RT-PCR), respectively, were inconsistent with a quantify variance of one or two orders of magnitude. Special emphasis was given to the counting advantages of RT-PCR based on the methanotrophic pmoA gene. Finally, the diversity and distribution of methanotrophic communities in the soil samples were analyzed by constructing clone libraries of functional gene. All 508-bp inserts in clones phylogenetically belonged to the methanotrophic pmoA gene with similarities from 83% to 100%. However, most of the similarities were below 96%. Five clone libraries of methanotrophs clearly showed that the anomalous methanotrophs (Methylosinus and Methylocystis) occupy the studied area.     

Low-temperature microbial degradation of crude oil products differing in the extent of condensation

Out of the 30 strains capable of oil degradation at 4-6 degrees C, four were selected by the ability to degrade 40% of the oil substrate present in the growth medium: Rhodococcus spp. DS-07 and DS-21 and Pseudomonas spp. DS-09 and DS-22. We studied the activity of these strains as degraders of oil products of various condensation degrees (crude oil, masut, petroleum oils, benzene resins and ethanol-benzene resins) at 4-6 degrees C. The maximum degrees of degradation of masut and ethanol-benzene resins were observed in Pseudomonas spp. DS-22 (17.2% and 5.2%, respectively). The maximum degradation of petroleum oils and benzene resins was observed in Rhodococcus spp. DS-07 (40% and 16.6%, respectively). The strains provide a basis for developing biodegrader preparations applicable to bioremediation of oil-polluted sites under the conditions of cold climate.     

微生物降解多环芳烃(PAHs)的研究进展

从多环芳烃(PAHs)的降解菌株的筛选、降解机制以及PAHs污染的生物修复等方面介绍了微生物降解PAHs的最新研究进展。     

多溴联苯醚的微生物降解机制研究进展

多溴联苯醚(PBDEs)是世界范围内广泛使用的一类溴代阻燃剂,在环境中被频繁检出。因其具有生物积累性、生物毒性和持久性等特点,如今PBDEs已成为全球分布的有机化学毒素。探究PBDEs的降解极为重要,文中从PBDEs微生物降解的角度出发,分别阐释了好氧条件和厌氧条件下细菌降解PBDEs的代谢途径研究进展,并结合原位降解研究推断古菌的降解潜能,比较分析了多种降解途径的特性和综合因素,同时对PBDEs降解微生物未来的研究趋势和PBDEs降解体系设计应用进行了展望。     

Compositions of microbial communities associated with oil and water in a mesothermic oil field

Samples of produced water and oil obtained from the Enermark field (near Medicine Hat, Alberta, Canada) were separated into oil and aqueous phases first gravitationally and then through centrifugation at 20°C in an atmosphere of 90% N₂ and 10% CO₂. Biomass that remained associated with oil after gravitational separation (1×g) was dislodged by centrifugation at 25,000×g. DNA was isolated from the aqueous and oil-associated biomass fractions and subjected to polymerase chain reaction amplification with primers targeting bacterial and archaeal 16S rRNA genes. DNA pyrosequencing and bioinformatics tools were used to characterize the resulting 16S rRNA gene amplicons. The oil-associated microbial community was less diverse than that of the aqueous phase and had consistently higher representation of hydrogenotrophs (methanogens of the genera Methanolobus and Methanobacterium and acetogens of the genus Acetobacterium), indicating the oil phase to be a primary source of hydrogen. Many known hydrocarbon degraders were also found to be oil-attached, e.g. representatives of the gammaproteobacterial genus Thalassolituus, the actinobacterial genus Rhodococcus and the alphaproteobacterial genera Sphingomonas, Brevundimonas and Stappia. In contrast, all eight representatives of genera of the Deltaproteobacteria identified were found to be associated with the aqueous phase, likely because their preferred growth substrates are mostly water-soluble. Hence, oil attachment was seen for genera acting on substrates found primarily in the oil phase.     

Application of a Doehlert experimental design to the optimization of microbial degradation of crude oil in sea water by continuous culture

Summary Crude oil was degraded by a mixed bacterial community grown in continuous culture on sea water. The fermentation process included an emulsification step prior to the introduction of the substrate in the reactor, with external cell recycling by a tangential-flow filtration system. Optimization of the fermentation technique was achieved by using the surface response methodology (Doehlert experimental design). Besides reducing the number of experiments, this approach allowed optimal experimental conditions to be chosen, for the particular goal: percent degradation of crude oil (80%), biomass (7.6 g·l^-1) and degradation rate (0.73 g·l^-1·h^-1). This biodegradation process could be used as a tool to fight against pollutions by petroleum products.     

Electricity generation using chocolate industry wastewater and its treatment in activated sludge based microbial fuel cell and analysis of developed microbial community in the anode chamber

Feasibility of using chocolate industry wastewater as a substrate for electricity generation using activated sludge as a source of microorganisms was investigated in two-chambered microbial fuel cell. The maximum current generated with membrane and salt bridge MFCs was 3.02 and 2.3 A/m², respectively, at 100 Ω external resistance, whereas the maximum current generated in glucose powered MFC was 3.1 A/m². The use of chocolate industry wastewater in cathode chamber was promising with 4.1 mA current output. Significant reduction in COD, BOD, total solids and total dissolved solids of wastewater by 75%, 65%, 68%, 50%, respectively, indicated effective wastewater treatment in batch experiments. The 16S rDNA analysis of anode biofilm and suspended cells revealed predominance of β-Proteobacteria clones with 50.6% followed by unclassified bacteria (9.9%), α-Proteobacteria (9.1%), other Proteobacteria (9%), Planctomycetes (5.8%), Firmicutes (4.9%), Nitrospora (3.3%), Spirochaetes (3.3%), Bacteroides (2.4%) and γ-Proteobacteria (0.8%). Diverse bacterial groups represented as members of the anode chamber community.     

Biochemical and genetic bases of microbial degradation of polychlorinated biphenyls (PCBs)

The microbial degradation of polychlorinated biphenyls (PCBs) has been extensively conducted by many workers, and the following general results have been obtained. (1) PCBs are degraded oxidatively by aerobic bacteria and other microorganisms such as white rot fungi. PCBs are also reductively dehalogenated by anaerobic microbial consortia. (2) The biodegradability of PCBs is highly dependent on chlorine substitution, i.e., number and position of chlorine. The degradation and dehalogenation capabilities are also highly strain dependent. (3) Biphenyl-utilizing bacteria can cometabolize many PCB congeners to chlorobenzoates by biphenl-catabolic enzymes. (4) Enzymes involved in the PCB degradation were purified and characterized. Biphenyl dioxygenase, ring-cleavage dioxygenase, and hydrolase are crystallized, and two ring-cleavage dioxygenases are being solved by x-ray crystallography. (5) The bph gene clusters responsible for PCB degradation are cloned from a variety of bacterial strains. The structure and function are analyzed with respect to the evolutionary relationship. (6) The molecular engineering of biphenyl dioxygenases is successfully performed by DNA shuffling, domain exchange, and subunit exchange. The evolved enzymes exhibit wide and enhanced degradation capacities for PCBs and other aromatic compounds.     

Characterization of microbial diversity and community in water flooding oil reservoirs in China

The diversity and distribution of bacterial and archaeal communities in four different water flooding oil reservoirs with different geological properties were investigated using 16S rDNA clone library construction method. Canonical correspondence analysis was used to analyze microbial community clustering and the correlation with environmental factors. The results indicated that the diversity and abundance in the bacterial communities were significantly higher than the archaeal communities, while both of them had high similarity within the communities respectively. Phylogenetic analysis showed that of compositions of bacterial communities were distinctly different both at phylum and genus level. Proteobacteria dominated in each bacterial community, ranging from 61.35 to 75.83?%, in which α-proteobacteria and γ-proteobacteria were the main groups. In comparison to bacterial communities, the compositions of archaeal communities were similar at phylum level, while varied at genus level, and the dominant population was Methanomicrobia, ranging from 65.91 to 92.74?% in the single oil reservoir. The factor that most significantly influenced the microbial communities in these reservoirs was found to be temperature. Other environmental factors also influenced the microbial communities but not significantly. It is therefore assumed that microbial communities are formed by an accumulated effect of several factors. These results are essential for understanding ecological environment of the water flooding oil reservoirs and providing scientific guidance to the performance of MEOR technology.     

十溴联苯醚降解菌群的降解特性与组成分析

[目的]针对水体沉积物中日益严重的多溴联苯醚污染问题,以电子垃圾污染河床沉积物为种源富集驯化获得的菌群Cf3,研究该菌群对十溴联苯醚的降解特性以及其菌群结构组成.[方法]通过GC-MS分析十溴联苯醚降解后低溴代产物组成,并测定其降解率;通过DGGE技术分析了该BDE-209降解菌群的结构组成.[结果]菌群Cf3具有较强降解BDE-209的能力,经过120 d的培养,初始量为2.6 μmol的BDE-209降解率达到80.03％,OD600从0.01增长到0.21,pH由初始的6.93增加到反应结束时的8.50.菌群Cf3经过单菌落分离,共获得10株可培养细菌,通过16S rRNA基因序列比对发现,其中6株与柠檬酸杆菌属(Citrobacter spp.)具有较高同源性,其余4株与产碱杆菌属(Alcaligenes spp.)较相似.进一步采用DGGE分析菌群Cf3的结构组成时发现,除了分离得到的2个菌属外,该菌群中还含有拟杆菌属(Wolinella spp.)、氨基酸球菌属(Acidaminococcus spp.),以及随着降解时间延长而消失的脱硫弧菌属(Desulfovibrio spp.)和醋杆菌属(Acetobacterium spp.).[结论]获得了具有较强多溴联苯醚降解能力的菌群,并分析了其降解特性和群落组成,为进一步开展溴代阻燃剂等持久性有机污染物的生物修复提供宝贵的菌种资源和科学数据.     

气态烃诱导下油气微生物数量及功能基因变化特征

【目的】烃类渗漏是地球化学循环中的自然垂直运移现象。油气微生物勘探技术就是通过检测油气微生物在烃类渗漏条件下形成的异常特征进而预测下伏油气藏。然而,上浮烃类比重小,使得油气微生物丰度小,缺乏对油气藏地表烃类与油气微生物的深入认识。【方法】本研究在人工模拟环境下,采用培养法和定量PCR对油气微生物数量和油气功能基因的变化特征进行研究。【结果】人工模拟的不同渗漏环境,在一定的驯化培养周期下分别考察甲烷氧化菌和丁烷氧化菌数量变化特征,甲烷氧化菌与丁烷氧化菌在不同烃源中呈现不同的发育情况;同时,在气态烃高浓度阳性对照和微渗漏条件下,油气指示基因pmo A与bom X基因丰度呈现增长现象,然而经过吹脱实验基因丰度仍能指示出曾经发育的油气微生物,在油气微生物勘探检测分析时间尺度上精度高于数量水平的检测。【结论】本研究考察了土壤中油气微生物的数量和功能基因变化特征,为烃类渗漏与油气微生物之间的相关性研究奠定了基础,为油气微生物勘探提供直接实验依据。     

The influence of water aeration by the phallus process on the Macrobenthic fauna (preliminary report)

A lowland brook-pond system, polluted with organic waste was aerated with a new aeration method. The macrobenthic fauna was investigated. Aeration proved to increase the total number of animals and the species diversity. The total number of individuals and the biomass was rather stable during the different seasons.