A kinetic model for surfactant inhibition of pentachlorophenol biodegradation

A kinetic model is used to describe the effect of the nonionic surfactant Tergitol NP-10 (TNP10) on pentachlorophenol (PCP) biodegradation by Sphingomonas chlorophenolica sp. strain RA2. Different initial biomass to initial substrate ratios ranging from 13 to 418 were tested with 23 TNP10 concentrations ranging from 0 to 1500 mg/L. Tests were also conducted at 10 degrees C and 20 degrees C. No PCP biodegradation inhibition was observed at concentrations below the critical micelle concentration (CMC) of 50 mg/L. TNP10 concentrations above 100 to 200 mg/L were increasingly inhibitory to PCP biodegradation rates. This inhibition was best described by the Monod kinetic equation wherein the effect of TNP10 inhibition is reflected in the half-saturation constant (Ks). The value of the Ks increased from between 1.5 and 13.5 mg/L with no surfactant present to 44 to 131 mg/L at 1000 mg/L TNP10. Using a standard competitive inhibition approach, the inhibition constant for TNP10 was approximately 100 mg/L at both 10 degrees C and 20 degrees C.     

Biodegradation of pentachlorophenol by the white rot fungus Phanerochaete chrysosporium

Extensive biodegradation of pentachlorophenol (PCP) by the white rot fungus Phanerochaete chrysosporium was demonstrated by the disappearance and mineralization of [14C]PCP in nutrient nitrogen-limited culture. Mass balance analyses demonstrated the formation of water-soluble metabolites of [14C]PCP during degradation. Involvement of the lignin-degrading system of this fungus was suggested by the fact the time of onset, time course, and eventual decline in the rate of PCP mineralization were similar to those observed for [14C]lignin degradation. Also, a purified ligninase was shown to be able to catalyze the initial oxidation of PCP. Although biodegradation of PCP was decreased in nutrient nitrogen-sufficient (i.e., nonligninolytic) cultures of P. chrysosporium, substantial biodegradation of PCP did occur, suggesting that in addition to the lignin-degrading system, another degradation system may also be responsible for some of the PCP degradation observed. Toxicity studies showed that PCP concentrations above 4 mg/liter (15 microM) prevented growth when fungal cultures were initiated by inoculation with spores. The lethal effects of PCP could, however, be circumvented by allowing the fungus to establish a mycelial mat before adding PCP. With this procedure, the fungus was able to grow and mineralize [14C]PCP at concentrations as high as 500 mg/liter (1.9 mM).     

Biodegradation of pentachlorophenol by the white rot fungus Phanerochaete chrysosporium.

Extensive biodegradation of pentachlorophenol (PCP) by the white rot fungus Phanerochaete chrysosporium was demonstrated by the disappearance and mineralization of [14C]PCP in nutrient nitrogen-limited culture. Mass balance analyses demonstrated the formation of water-soluble metabolites of [14C]PCP during degradation. Involvement of the lignin-degrading system of this fungus was suggested by the fact the time of onset, time course, and eventual decline in the rate of PCP mineralization were similar to those observed for [14C]lignin degradation. Also, a purified ligninase was shown to be able to catalyze the initial oxidation of PCP. Although biodegradation of PCP was decreased in nutrient nitrogen-sufficient (i.e., nonligninolytic) cultures of P. chrysosporium, substantial biodegradation of PCP did occur, suggesting that in addition to the lignin-degrading system, another degradation system may also be responsible for some of the PCP degradation observed. Toxicity studies showed that PCP concentrations above 4 mg/liter (15 microM) prevented growth when fungal cultures were initiated by inoculation with spores. The lethal effects of PCP could, however, be circumvented by allowing the fungus to establish a mycelial mat before adding PCP. With this procedure, the fungus was able to grow and mineralize [14C]PCP at concentrations as high as 500 mg/liter (1.9 mM).     

Biodegradation of pentachlorophenol in soil: the response to physical, chemical, and biological treatments

The effects of physical, chemical, and biological treatments on biodegradation of pentachlorophenol (PCP) were studied in a silt-loam soil contaminated with 175 mg PCP/kg and uniformly 14C-labelled PCP. Biodegradation of 14C-labelled PCP and technical-grade PCP were monitored over 210 days incubation. Mineralization of labelled PCP was significantly (p=0.05) influenced by soil treatments. Negligible biodegradation occurred in either the sterile control soil or the uninoculated control soil, with less than 1% of added 14C recovered as 14 CO2. Inoculation of unamended soil with a strain of Flavobacterium (ATCC 39723) known to degrade PCP increased biodegradation of PCP; approximately 60% of the [14C]PCP was recovered as 14CO2. Increased soil water content (60% versus 30% w/w) enhanced biodegradation (67% recovery of 14C as CO2), while increased chloride ion concentration and anoxic conditions were inhibitory (20 and 1% recoveries, respectively). Residual soil PCP concentrations were also influenced by various treatments. In the sterile control soil and noninoculated control, after 210 days incubation, concentrations of PCP were 143 and 1223 mg/kg, respectively, while the PCP concentration in the inoculated soil was 21 mg/kg. When soil organic matter was increased by adding finely ground red clover leaf and stem material, the residual PCP concentration was reduced to 6 mg/kg after 210 days. Increased soil water content resulted in a residual PCP concentration of 5 mg/kg. High-pressure liquid chromatography of soil extracts revealed no accumulation of partial PCP degradation products. The results indicated that biodegradation of PCP in soil was significantly influenced by various soil amendments.     

五氯酚在污染沉积物泥浆固液两相中厌氧生物降解

研究了污染沉积物泥浆液、固两相五氯酚(PCP)厌氧生物降解.结果表明,投加10g·kg^-1厌氧颗粒污泥,经31d处理泥浆液、固两相PCP降解率达98.9%,平均降解速率达到80mg·kg^-1·d^-1,对照处理平均降解速率仅为4.4mg·kg^-1·d^-1,颗粒污泥生物强化作用明显.作为泥浆修复过程的调控因子,有机溶剂、共基质和表面活性剂对PCP降解效应不同,投加乙醇,可提高PCP解吸和降解速率,4d内两相PCP降解速率达到54.3mg·kg^-1·d^-1;而投加共基质和非离子表面活性剂乙二醇丁醚后,液、固两相PCP降解均出现迟滞,两者均不同程度地抑制PCP降解.     

Growth kinetics of Pseudomonas putida G7 on naphthalene and occurrence of naphthalene toxicity during nutrient deprivation

The objectives of this work were (1) to demonstrate how the chemostat approach could be modified to allow determination of kinetic parameters for a sparingly soluble, volatile substrate such as naphthalene and (2) to examine the influence of the interactions of various nutrients on possible growth-inhibitory effects of naphthalene. Pseudomonas putida G7 was used as a model naphthalene-degrading microorganism. Naphthalene was found to be toxic to P. putida G7 in the absence of a nitrogen source or oxygen. The death rate of cells grown on minimal medium plus naphthalene and then exposed to naphthalene under anoxic conditions was higher than that observed under oxic conditions in the absence of a nitrogen source. The presence of necessary nutrients for the biodegradation of PAH compounds is indicated to be important for the survival of microorganisms that are capable of PAH degradation. The amounts of ammonia and oxygen necessary for naphthalene biodegradation and for suppression of naphthalene toxicity were calculated from growth yield coefficients. A chemostat culture of P. putida G7 using naphthalene as a carbon and energy source was accomplished by using a feed augmented with a methanol solution of naphthalene so as to provide sufficient growth to allow accurate evaluation of kinetic parameters. When naphthalene was the growth-limiting substrate, the degradation of naphthalene followed Monod kinetics. Maximum specific growth rate (micrometer) and Monod constant (Ks) were 0.627 +/- 0.007 h-1 and 0.234 +/- 0.0185 mg/L, respectively. The evaluation of biodegradation parameters will allow a mathematical model to be applied to predict the long-term behavior of PAH compounds in soil when combined with PAH transport parameters.     

Multisubstrate monod kinetic model for simultaneous degradation of chlorophenol mixtures

Chlorophenols (CPs) are persistent and highly toxic compounds rated as priority pollutants by the Environmental Protection Agency (EPA). Frequently, these compounds are present as mixtures of CPs in industrial wastewaters. Therefore the study of biodegradation on mixed pollutants is an important aspect of biodegradation and wastewater treatment. In this work, we studied the multisubstrate degradation of CPs by a mixed culture of Pseudomonas aeruginosa and a novel Acromobacter sp. capable of using pentachlorophenol (PCP), 2,4,6 trichlorophenol (2,4,6 TCP) and 2,3,5,6 tetrachlorophenol (2,3,5,6 TeCP) as the sole sources of carbon and energy. The main objective of this work was to evaluate the effect of substrate mixtures on the degradation kinetics of PCP. Batch experiments were conducted with each CP separately and in mixtures of PCP + 2,4,6 TCP, PCP + 2,3,5,6 TeCP, and PCP + 2,4,6 TCP + 2,3,5,6 TeCP. Based upon our results we have concluded that the simultaneous degradation of CPs is a key factor contributing to the improvement of PCP degradation. The kinetic parameters for PCP and 2,4,6 TCP were obtained by fitting the data to a Monod kinetics model. Using such parameters, the model was able to predict simultaneous multisubstrate degradation of PCP with others CPs.     

Degradation of chlorinated phenols by a pentachlorophenol-degrading bacterium

A pentachlorophenol (PCP)-degrading Flavobacterium sp. was tested for its ability to dechlorinate other chlorinated phenols by using resting cells that had been grown in the presence or absence of PCP. Phenols with chlorine atoms at positions 2 and 6 of the phenol ring were dechlorinated completely by PCP-induced cells. Other chlorinated phenols were not significantly mineralized. When PCP was added to a culture growing on L-glutamate, there was a lag period before the start of PCP degradation. When similar cells were treated with chloramphenicol prior to the addition of PCP, they did not degrade added PCP, even after prolonged incubations. Thus, the enzymes necessary for PCP degradation appeared to be inducible. Suspensions of cells grown in the presence of 2,4,6-trichlorophenol or 2,3,5,6-tetrachlorophenol did not show a lag period for mineralization of PCP, 2,4,6-trichlorophenol, or 2,3,5,6-tetrachlorophenol, indicating that one enzyme system probably was induced for the biodegradation of all three compounds. Nondegradable chlorophenols were toxic toward the Flavobacterium sp., probably acting as uncouplers of oxidative phosphorylation.     

Degradation of chlorinated phenols by a pentachlorophenol-degrading bacterium.

A pentachlorophenol (PCP)-degrading Flavobacterium sp. was tested for its ability to dechlorinate other chlorinated phenols by using resting cells that had been grown in the presence or absence of PCP. Phenols with chlorine atoms at positions 2 and 6 of the phenol ring were dechlorinated completely by PCP-induced cells. Other chlorinated phenols were not significantly mineralized. When PCP was added to a culture growing on L-glutamate, there was a lag period before the start of PCP degradation. When similar cells were treated with chloramphenicol prior to the addition of PCP, they did not degrade added PCP, even after prolonged incubations. Thus, the enzymes necessary for PCP degradation appeared to be inducible. Suspensions of cells grown in the presence of 2,4,6-trichlorophenol or 2,3,5,6-tetrachlorophenol did not show a lag period for mineralization of PCP, 2,4,6-trichlorophenol, or 2,3,5,6-tetrachlorophenol, indicating that one enzyme system probably was induced for the biodegradation of all three compounds. Nondegradable chlorophenols were toxic toward the Flavobacterium sp., probably acting as uncouplers of oxidative phosphorylation.     

Apparent zero-order kinetics of phenol biodegradation by substrate-inhibited microbes at low substrate concentrations

The reaction kinetics for phenol biodegradation at low substrate concentrations can be estimated based on the analysis of changes in the dissolved oxygen concentration in the bulk liquid during biodegradation. The measured oxygen concentration changes with an interesting behavior as biodegradation proceeds. The oxygen concentration in the bulk liquid decreases rapidly in the early stages of degradation and subsequently decreases linearly and then rapidly recovers to the initial saturated level. Taking into account the oxygen transfer rate between gas and liquid phases and oxygen consumption rate by microbes, the change in the dissolved oxygen concentration can be simulated with an unsteady state mass balance equation and three kinetic models for the rate of phenol metabolism: a substrate-inhibited model; a zero-order model; and a combined model. In the combined model, it is assumed that, at phenol concentrations above 10 mg/L, the degradation rate is expressed by a substrate-inhibited model; whereas at concentrations below 10 mg/L the zero-order model is applied. It was found that the characteristics of the change in the dissolved oxygen concentration, especially the rapid increase at the end of degradation, can only be described by the combined kinetic model. This result suggests that conventional Haldane-type kinetics would be unsuitable for estimating the phenol consumption rate at low phenol concentrations, in particular, at concentrations less than 10 mg/L. (c) 1996 John Wiley & Sons, Inc.     

一株高效丙烯腈降解细菌Rhodococus rhodochrous BX2的丙烯腈降解条件优化

【目的】以丙烯腈为目标污染物,利用实验室已筛选获得的一株高效腈降解菌Rhodococus rhodochrous BX2,研究其对丙烯腈的降解特性,优化降解条件以提高菌株对丙烯腈的降解能力。【方法】通过单因素试验和响应面分析相结合的方法优化Rhodococus rhodochrous BX2对丙烯腈的降解条件。考察外加碳、氮源对BX2的生长及丙烯腈降解的影响,并确定其在丙烯腈合成废水中对丙烯腈的处理效果。【结果】菌株BX2优化后的最佳降解条件为:底物浓度403.51 mg/L、p H 7.44、温度34.46°C,在此条件下丙烯腈的降解率为95.1%。外加碳源为葡萄糖,或外加氮源为氯化铵对菌株生长及丙烯腈降解有明显的促进作用。菌株Rhodococus rhodochrous BX2能够高效降解合成废水中的丙烯腈,在30 h时其丙烯腈降解率可达89.4%。【结论】降解条件优化以及外源物质的添加强化了菌株对丙烯腈合成废水的处理效果,为生物法处理丙烯腈废水新方法的开发提供技术支持。     

Characterization of a novel Pseudomonas sp. that mineralizes high concentrations of pentachlorophenol.

A pentachlorophenol (PCP)-mineralizing bacterium was isolated from polluted soil and identified as Pseudomonas sp. strain RA2. In batch cultures, Pseudomonas sp. strain RA2 used PCP as its sole source of carbon and energy and was capable of completely degrading this compound as indicated by radiotracer studies, stoichiometric release of chloride, and biomass formation. Pseudomonas sp. strain RA2 was able to mineralize a higher concentration of PCP (160 mg liter-1) than any previously reported PCP-degrading pseudomonad. At a PCP concentration of 200 mg liter-1, cell growth was completely inhibited and PCP was not degraded, although an active population of Pseudomonas sp. RA2 was still present in these cultures after 2 weeks. The inhibitory effect of PCP was partially attributable to its effect on the growth rate of Pseudomonas sp. strain RA2. The highest specific growth rate (mu = 0.09 h-1) was reached at a PCP concentration of 40 mg liter-1 but decreased at higher or lower PCP concentrations, with the lowest mu (0.05 h-1) occurring at 150 mg liter-1. Despite this reduction in growth rate, total biomass production was proportional to PCP concentration at all PCP concentrations degraded by Pseudomonas sp. RA2. In contrast, final cell density was reduced to below expected values at PCP concentrations greater than 100 mg liter-1. These results indicate that, in addition to its effect as an uncoupler of oxidative phosphorylation, PCP may also inhibit cell division in Pseudomonas sp. strain RA2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of a novel Pseudomonas sp. that mineralizes high concentrations of pentachlorophenol.

A pentachlorophenol (PCP)-mineralizing bacterium was isolated from polluted soil and identified as Pseudomonas sp. strain RA2. In batch cultures, Pseudomonas sp. strain RA2 used PCP as its sole source of carbon and energy and was capable of completely degrading this compound as indicated by radiotracer studies, stoichiometric release of chloride, and biomass formation. Pseudomonas sp. strain RA2 was able to mineralize a higher concentration of PCP (160 mg liter-1) than any previously reported PCP-degrading pseudomonad. At a PCP concentration of 200 mg liter-1, cell growth was completely inhibited and PCP was not degraded, although an active population of Pseudomonas sp. RA2 was still present in these cultures after 2 weeks. The inhibitory effect of PCP was partially attributable to its effect on the growth rate of Pseudomonas sp. strain RA2. The highest specific growth rate (mu = 0.09 h-1) was reached at a PCP concentration of 40 mg liter-1 but decreased at higher or lower PCP concentrations, with the lowest mu (0.05 h-1) occurring at 150 mg liter-1. Despite this reduction in growth rate, total biomass production was proportional to PCP concentration at all PCP concentrations degraded by Pseudomonas sp. RA2. In contrast, final cell density was reduced to below expected values at PCP concentrations greater than 100 mg liter-1. These results indicate that, in addition to its effect as an uncoupler of oxidative phosphorylation, PCP may also inhibit cell division in Pseudomonas sp. strain RA2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modeling substrate interactions during the biodegradation of mixtures of toluene and phenol by Burkholderia species JS150

The biodegradation kinetics of toluene, phenol, and a mixture of toluene and phenol by Burkholderia species JS150 was measured and modeled. Both of these compounds can serve as the sole source of carbon and energy for this microorganism. The single-substrate biodegradation kinetics was described well using the Monod model, with model constants of mu(max,T) = 0.39 h(-1) and K(S,T) = 0.011 mM for growth on toluene and mu(max,P) = 0.309 h(-1) and K(S,P) = 0.0054 mM for growth on phenol. Degradation of the mixture of toluene and phenol followed simultaneous utilization kinetics with toluene being the preferred substrate. Toluene was found to inhibit the rate of utilization of phenol while the presence of phenol had little effect on the rate of degradation of toluene. Of the kinetic models that were tested, one developed for microbial degradation of multiple substrates was able to describe substrate interactions and to model the mixture utilization by strain JS150. Simple competitive, noncompetitive, or uncompetitive substrate kinetics were not sufficient to describe the observed inhibitory interactions.     

壳聚糖固定化气单胞菌处理餐厨高油脂废水

为有效解决餐厨废水中的高油脂对下游处理工艺的严重影响,本研究以筛选获得的一株高效的油脂降解菌株嗜糖气单胞菌Aeromonas allosaccarophila CY-01为研究对象,以壳聚糖为载体材料,对其进行固定化包埋制备壳聚糖-气单胞菌小球(CH-CY01);探究CH-CY01小球的油脂降解效率以及性能影响评估。研究结果表明,经壳聚糖固定后的菌株CY-01其细胞的生长活性几乎不受影响,对大豆油脂的最大降解率为89.7%;相比于未固定的细胞,CH-CY01在0.5%NaCl的盐度条件下对油脂的降解效率显著提高了20%;在浓度为1 mg/L的表面活性剂(十二烷基苯磺酸钠)存在条件下,CH-CY01对油脂的降解效率显著提高了40%。以餐饮高油脂污水为处理对象,结果显示经添加1%(V/V)的CH-CY01小球处理7 d后,超过80%以上的固态油脂被降解,明显高于未固定的CY-01。综上所述,经壳聚糖固定包埋的CH-CY01小球显著提高了菌株的生存能力和油脂降解效率,对于高油脂餐饮污水的高效处理具有较大的应用潜力。     

表面活性剂对分枝杆菌KR2菌株降解菲的影响

采用同位素示踪方法,从表面活性剂的浓度、离子类型和直链长度三方面研究了表面活性剂对分枝杆菌KR2菌株降解菲的影响。结果表明,表面活性剂的存在不能促进KR2菌对菲的降解;高浓度表面活性剂(≥20mg·L^-1)的存在,使菲的降解出现延迟期,非离子表面活性剂Tween80在低浓度时(≤10mg·L^-1)可以优先作为营养基质被分枝杆菌KR2菌株利用,表面活性剂的离子类型对菲降解的抑制作用的顺序为阳离子表面活性剂TDTMA>阴离子表面活性剂LAS>非离子表面活性剂Tween80,表面活性剂的直链长度对菲降解的影响为直链越短,对微生物的毒性越大,菲降解得越不完全。     

Batch kinetics of Pseudomonas sp. growth on benzene. Modeling of product and substrate inhibitions

Batch tests of benzene degradation were performed in liquid phase at 30 degrees C, pH 6.8 +/- 0.2, and 200 rpm in two 3-L stirred tank bioreactors, using the benzene-degrading bacterium Pseudomonas sp. NCIMB 9688. A relatively high starting biomass level (220-270 mg(X)/L) and starting benzene concentration ranging from 20 to 200 mg(S)/L were selected as conditions to investigate possible inhibition phenomena. Volumetric as well as specific rates of biomass formation and substrate consumption were calculated from experimental data of both growth and benzene degradation and used to propose and check a new overall kinetic model for cell growth simultaneously accounting for both product and substrate inhibitions. The results of the present study evidenced the occurrence of a competitive-type product inhibition due to 2-hydroxymuconic semialdehyde (K(iP)' = 0.902 mg(S)/L), which was stronger than the uncompetitive-type inhibition exerted by substrate (K(iS) = 7.69 mg(S)/L).     

Effect of adsorbents on degradation of toxic organic compounds by coimmobilized systems

The use of coimmobilized systems for treatment of toxic organic compounds has been proposed. The proposed approach combines the use of adsorbents and laboratory identified microorganisms immobilized in a protective permeable barrier to achieve a greater degree of control over the remediation process. This study was launched to understand the effect of adsorbents and changes in adsorption on the degradation of toxic compounds by coimmobilized systems. The specific case studied involved the degradation of pentachlorophenol (PCP) by Arthrobacter (ATCC 33790) coimmobilized with powdered activated carbon within calcium alginate capsules.The design parameters studied included adsorbent content and type as well as the effect of solution pH and surfactant concentration on adsorption and biodegradation. It was found that the equilibrium adsorption behavior of PCP was strongly influenced by solution pH and surfactant concentration. A mathematical model was developed that combined the physical processes of mass transfer and adsorption with biological degradation of PCP. The model was used to predict the effect of various parameters on the degradation of PCP. Based on model predictions, the degradation of PCP. Based on model predictions, the degradation of PCP was strongly dependent on variations in adsorbent capacity and affinity for this contaminant.     

Activation of an indigenous microbial consortium for bioaugmentation of pentachlorophenol/creosate contaminated soils

Soil activation, a concept based on the cultivation of biomass from a fraction of a comtaminated soil for subsequent use as an inoculum for bioaugmentation of the same soil, was studied as a method for the aerobic biodegradation of pentachlorophenol (PCP) and polycyclic hydrocarbons (PAH) in contaminated soils. A microbial consortium able to degrade PCP and PAH in contaminated soil from wood-preserving facilities was isolated and characterized for PCP degradation and resistance. To obtain an active consortium from the contaminated soil in a fed-batch bioreactor, the presence of soil as a support or source of nutrients was found to be essential. During the 35 days of bioreactor operation, residual PCP in solution remained near zero up to a loading rate of 700mg/l per day. The PCP meneralization rate increased from 70 mg/l per day when no PCP was added to the bioreactor to 700 mg/l per day at the maximum loading rate. The consortium tolerated a PCP concentration of 400 mg/l in batch experiments. Production of a PCP-degrading consortium in a fed-batch slurry bioreactor enhanced the activity of PCP biodegradation by a factor of ten. PAH biodegradation increased, during the same time period, by a factor of 30 and 81 for phenanthrene and pyrene, respectively. Preliminary laboratory-scale results indicated that a significant reduction in the time required for degradation of PCP and PAH in contaminated soil could be achieved using activated soil as an inoculum.Issued as NRC 33861 correspondence to: R. Samson