生物降解对黑碳及土壤上苯酚脱附行为的影响

农业土壤和黑碳(BC)两种不同的吸附剂吸附苯酚平衡后分离,每组一部分不做处理,另一部分通过加入无酚灭菌溶液脱附平衡后分离,制备得到在不同吸附位点上吸附有苯酚的两类不同类型的4种吸附苯酚的吸附剂,研究了在不同Pseudomonasputida ATCC 11172菌密度条件下吸附在这4种吸附剂上的苯酚的脱附行为.结果表明,土壤及BC对苯酚的吸附均呈现明显的非线性,可用Freundlich模型描述.吸附态的苯酚能否被微生物利用取决于微生物及吸附剂的性质,BC具有发达的微孔结构,微孔小于假单胞菌细胞尺寸,导致假单胞菌无法直接利用吸附在BC上的苯酚;土壤基本无微孔结构,微生物较易与吸附的苯酚发生表面接触,直接利用吸附态苯酚.BC和土壤上的吸附态苯酚的脱附行为能用三元位点模型很好地描述,模型计算结果表明BC上的苯酚脱附主要受慢速脱附和极慢速脱附控制,微生物降解速率受脱附控制,降解可加速BC上的慢速脱附和极慢速脱附;土壤上的苯酚脱附主要受快速脱附控制,微生物降解不受脱附速率限制,对土壤上的脱附行为基本无影响.     

Noise analysis and relaxation experiments of transport of hydrophobic anions across lipid membranes at equilibrium and nonequilibrium

Under equilibrium and nonequilibnum steady-stale conditions the spectral intensity of current noise S_J(f) generated by the transport of hydrophobic unions across lipid bilayer membranes was investigated. The experimental results were compared with different reaction models S_J(f) showed a characteristic increase proportional to f² between frequency-independent tails at low and high frequencies. This gradient was found to be independent of applied voltage which indicates the contribution of a single voltage-dependent reaction step of ion translocation across the membrane From the shape of S_J(f) at low frequencies the rate constant of ion desorption from the membrane into the aqueous phase could be estimated. Unambiguous evidence for the application of a general model, which includes the coupling of slow ion diffusion in the aqueous phase to ion adsorption/desorption at the membrane interface, could not be obtained from the low-frequency shape of S_J(f). The shot noise of this ion transport determines the amplitude of S_J(f) at high frequencies which decreases with increasing voltage applied. Analysis of voltage-jump current-relaxation experiments and of current noise carried cut on one membrane yielded significant differences of the derived ion partition coefficient. This deviation is qualitatively described on the basis of incomplete reaction steps.     

Kinetics and pathway of biodegradation of dibutyl phthalate by Pleurotus ostreatus

Dibutyl phthalate (DBP) is a plasticizer, whose presence in the environment as a pollutant has attained a great deal of attention due to its reported association with endocrine system disturbances on animals. Growth parameters, glucose uptake, percentage of removal efficiency (%E) of DBP, biodegradation constant of DBP (k) and half-life of DBP biodegradation (t_1/2) were evaluated for Pleurotus ostreatus grown on media containing glucose and different concentrations of DBP (0, 500 and 1000 mg l^?1). P. ostreatus degraded 99.6 % and 94 % of 500 and 1000 mg of DBP l^?1 after 312 h and 504 h, respectively. The k was 0.0155 h^?1 and 0.0043 h^?1 for 500 and 1000 mg of DBP l^?1, respectively. t_1/2 was 44.7 h and 161 h for 500 and 1000 mg of DBP l^?1, respectively. Intermediate compounds of biodegraded DBP were identified by GC-MS and a DBP biodegradation pathway was proposed using quantum chemical calculation. DBP might be metabolized to benzene and acetyl acetate, the first would be oxidated to muconic acid and the latter would enter into the Krebs cycle. P. ostreatus has the ability to degrade DBP and utilizes it as source of carbon and energy.     

Low spring constant regulates P-selectin-PSGL-1 bond rupture

Forced dissociation of selectin-ligand bonds is crucial to such biological processes as leukocyte recruitment, thrombosis formation, and tumor metastasis. Although the bond rupture has been well known at high loading rate r_f (≥10² pN/s), defined as the product of spring constant k and retract velocity v, how the low r_f (<10² pN/s) or the low k regulates the bond dissociation remains unclear. Here an optical trap assay was used to quantify the bond rupture at r_f ≤ 20 pN/s with low k (∼10⁻³-10⁻² pN/nm) when P-selectin and P-selectin glycoprotein ligand 1 (PSGL-1) were respectively coupled onto two glass microbeads. Our data indicated that the bond rupture force f retained the similar values when r_f increased up to 20 pN/s. It was also found that f varied with different combinations of k and v even at the same r_f. The most probable force, f*, was enhanced with the spring constant when k < 47.0 × 10⁻³ pN/nm, indicating that the bond dissociation at low r_f was spring constant dependent and that bond rupture force depended on both the loading rate and the mechanical compliance of force transducer. These results provide new insights into understanding the P-selectin glycoprotein ligand 1 bond dissociation at low r_f or k.     

Comparison of p-Nitrophenol Biodegradation in Field and Laboratory Test Systems

Acclimation of microbial communities exposed to p-nitrophenol (PNP) was measured in laboratory test systems and in a freshwater pond. Laboratory tests were conducted in shake flasks with water, shake flasks with water and sediment, eco-cores, and two sizes of microcosm. The sediment and water samples used in the laboratory experiments were obtained from the pond. After a 6-day acclimation period, PNP was biodegraded rapidly in the pond. When the pond was treated with PNP a second time, biodegradation began immediately. The acclimation periods in laboratory test systems that contained sediment were similar to that in the pond. The acclimation period was threefold longer in shake flasks without sediment. PNP was biodegraded more slowly by microbial communities acclimated in the laboratory than it was in the pond, and the rate of biodegradation varied with the type of test. The number of bacteria able to mineralize PNP increased by 3 orders of magnitude in the pond during the acclimation period. Similar increases accompanied acclimation in the laboratory systems.     

Tenax TA extraction to understand the rate-limiting factors in methyl-β-cyclodextrin-enhanced bioremediation of PAH-contaminated soil

The effectiveness of many bioremediation systems for PAH-contaminated soil may be constrained by low contaminant bioaccessibility due to limited aqueous solubility or large sorption capacity. Information on the extent to which PAHs can be readily biodegraded is of vital importance in the decision whether or not to remediate a contaminated soil. In the present study the rate-limiting factors in methyl-β-cyclodextrin (MCD)-enhanced bioremediation of PAH-contaminated soil were evaluated. MCD amendment at 10 % (w/w) combined with inoculation with the PAH-degrading bacterium Paracoccus sp. strain HPD-2 produced maximum removal of total PAHs of up to 35 %. The desorption of PAHs from contaminated soil was determined before and after 32 weeks of bioremediation. 10 % (w/w) MCD amendment (M2) increased the Tenax extraction of total PAHs from 12 to 30 % and promoted degradation by up to 26 % compared to 6 % in the control. However, the percentage of Tenax extraction for total PAHs was much larger than that of degradation. Thus, in the control and M2 treatment it is likely that during the initial phase the bioaccessibility of PAHs is high and biodegradation rates may be limited by microbial processes. On the other hand, when the soil was inoculated with the PAH-degrading bacterium (CKB and MB2), the slowly and very slowly desorbing fractions (F _sl and F _vl ) became larger and the rate constants of slow and very slow desorption (k _sl and k _vl ) became extremely small after bioremediation, suggesting that desorption is likely rate limiting during the second, slow phase of biotransformation. These results have practical implications for site risk assessment and cleanup strategies.     

Biodegradation of nonylphenol ethoxylates by Bacillus sp. LY capable of heterotrophic nitrification

Biodegradation of nonylphenol ethoxylates (NPEOs) by Bacillus sp. LY, with heterotrophic nitrification ability was investigated. The results showed that NPEOs were readily degraded by Bacillus sp. LY with more than 80% of the total NPEOs being removed within 7 days. Heterotrophic nitrogen removal occurred simultaneously during the biodegradation period of NPEOs. NPEOs were biodegraded through a nonoxidative pathway, through which NPEOs were degraded via sequential removal of ethoxyl units to the nonylphenol. To the authors' knowledge, it is the first report on the biodegradation of NPEO contaminants by a microorganism capable of heterotrophic nitrogen removal.     

Life Table and Sensitivity Analysis as Fitness Evaluation Method of Fenpyroximate and Pyridaben Resistant Twospotted Spider Mite (Tetranychus urticae Koch)

Fitness associated with pesticide resistance was assessed in twospotted spider mites, Tetranychus urticae Koch, using life table analysis. Two strains resistant to fenpyroximate (FR) and pyridaben (PR), and one susceptible strain (S) were included in this study. Two reciprocal crosses (FR♂xS♀ and PR♂xS♀) were established by conventional crossing procedure. Intrinsic rate of natural increase (r_m) was used as a comparative parameter of reproductive fitness among 3 parent strains (FR, PR, and S) and two reciprocal crosses. Sensitivity analysis was performed to evaluate significances of biological factors contributing to r_m. The r_m values were not significantly different from each other, with an exception of FR♂xS♀ cross and ranged from 0.250 to 0.274 per day. Sensitivity analysis revealed that birth rate (b) and mortality (μ) effects could account for the effect on r_m in the two resistant strains. Contributions of b and μ to r_m was markedly different in two resistant strains; high contribution in b and low in μ. Age at the first reproduction (t) and age at the last reproduction (t_ω) made roughly equal contributions to r_m between the strains and the crosses. This study clearly showed that how r_m was affected by various biological factors and provided a basic analytical tool for pesticide resistant management.     

Degradation of bisphenol A and nonylphenol by nitrifying activated sludge

Nitrifier-enriched activated sludge was used in batch degradation of bisphenol A (BPA) and nonylphenol (NP) to verify if ammonium-oxidizing activity within nitrifiers is responsible for the biodegradation of those compounds. Decreases in both BPA and NP concentrations occurred simultaneously with ammonium (NH₄⁺) oxidation into nitrate (NO₃⁻) by nitrifying sludge. However, when ammonium was replaced by nitrite (NO₂⁻) in the medium, an acclimation period was required prior onset of significant degradation of BPA and NP. In the presence of inhibitors such as allylthiourea or Hg₂SO₄, BPA and/or NP reduction decreased significantly, implying that removal of BPA and NP was mostly mediated by biological activity rather than by physicochemical adsorption onto sludge flocs.     

Sorption and ecotoxicity of pentachlorophenol polluted sediment amended with rice-straw derived biochar

To investigate the feasibility of using biochar to control organic pollutants in sediments, we extracted biochar from rice-straw combustion residues (RBC) and studied its adsorption ability and effect on seed germination ecotoxicity of pentachlorophenol (PCP). The results showed that the Freundlich and dual-mode models could describe all the sorption isotherm data well, and the log K_OC values increased with increasing RBC content. With 50 mg kg⁻¹ PCP in the sediment, a significant seed growth inhibition (P < 0.01) was observed. The addition of 2.0% RBC lowered the PCP concentration in the extraction liquid from 4.53 to 0.17 mg L⁻¹ and increased the germination rate and root length significantly. Furthermore, it was found that the addition of RBC had no toxic but stimulative effect on root elongation. Consequently, RBC could serve as a potential supersorbent for the remediation of organic pollution in situ.     

Forced-unfolding and force-quench refolding of RNA hairpins

Nanomanipulation of individual RNA molecules, using laser optical tweezers, has made it possible to infer the major features of their energy landscape. Time-dependent mechanical unfolding trajectories, measured at a constant stretching force (f_S) of simple RNA structures (hairpins and three-helix junctions) sandwiched between RNA/DNA hybrid handles show that they unfold in a reversible all-or-none manner. To provide a molecular interpretation of the experiments we use a general coarse-grained off-lattice Gō-like model, in which each nucleotide is represented using three interaction sites. Using the coarse-grained model we have explored forced-unfolding of RNA hairpin as a function of f_S and the loading rate (r_f). The simulations and theoretical analysis have been done both with and without the handles that are explicitly modeled by semiflexible polymer chains. The mechanisms and timescales for denaturation by temperature jump and mechanical unfolding are vastly different. The directed perturbation of the native state by f_S results in a sequential unfolding of the hairpin starting from their ends, whereas thermal denaturation occurs stochastically. From the dependence of the unfolding rates on r_f and f_S we show that the position of the unfolding transition state is not a constant but moves dramatically as either r_f or f_S is changed. The transition-state movements are interpreted by adopting the Hammond postulate for forced-unfolding. Forced-unfolding simulations of RNA, with handles attached to the two ends, show that the value of the unfolding force increases (especially at high pulling speeds) as the length of the handles increases. The pathways for refolding of RNA from stretched initial conformation, upon quenching f_S to the quench force f_Q, are highly heterogeneous. The refolding times, upon force-quench, are at least an order-of-magnitude greater than those obtained by temperature-quench. The long f_Q-dependent refolding times starting from fully stretched states are analyzed using a model that accounts for the microscopic steps in the rate-limiting step, which involves the trans to gauche transitions of the dihedral angles in the GAAA tetraloop. The simulations with explicit molecular model for the handles show that the dynamics of force-quench refolding is strongly dependent on the interplay of their contour length and persistence length and the RNA persistence length. Using the generality of our results, we also make a number of precise experimentally testable predictions.     

Influence of NH3/CO2 Modification on the Characteristic of Biochar and the CO2 Capture

This paper was aimed to study the influence of modification of biochar on the performance of CO₂ adsorption. Biochar, obtained from cotton stalk pyrolysis in a fixed bed reactor, was modified with ammonia and CO₂. The physicochemical properties of biochars were characterized by the Fourier transform infrared spectroscopy and automatic adsorption equipment (Micromeritics, ASAP 2020, USA). CO₂ adsorption of biochar was performed in thermogravimetric analyzer. The results showed that the surface area of char was increased significantly by CO₂ modification, while N-contained compound on char surface was enriched obviously by NH₃ modification. CO₂ adsorption of biochar increased greatly with CO₂ and NH₃ modification. CO₂ adsorption was mainly attributed to physical adsorption at 20 °C, and the adsorption quantity (maximum = 99 mg/g) was proportional to the micropore volume of the char. However, at 120 °C, molecular thermal motion increase, chemical adsorption start to play a dominated role, and the adsorption was directly proportional to the N content of this char.     

Use of conventional or non-conventional treatments of biochar for lipase immobilization

The objective of this work was to evaluate the influence of dichloromethane (CH₂Cl₂), potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) in the treatment of biochar from guava seeds on conventional and non-conventional techniques (ultrasound and microwave) for the immobilization of Burkholderia cepacia lipase (BCL) by physical adsorption. The effects of the different treatments on the physical and chemical properties of the biochar were evaluated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The immobilization of the BCL on the biochar was evaluated in hydrolysis reactions of olive oil. The conventional treatment of the biochar with KOH showed increased modification on the surface of the biochar, which presented a highly porous surface, and a greater activity for the immobilized biocatalyst compared with the other treatments. The results revealed the potential of biochar as a support novelty for the immobilization of enzymes and for their application in biocatalysis.     

UV photolysis for accelerated quinoline biodegradation and mineralization

Sequentially and intimately coupled photolysis with biodegradation were evaluated for their ability to accelerate quinoline-removal and quinoline-mineralization kinetics. UV photolysis sequentially coupled to biodegradation significantly improved biomass-growth kinetics, which could be represented well by the Aiba self-inhibition model: UV photolysis increased the maximum specific growth rate (μ _max) by 15 %, and the inhibition constant (K _SI) doubled. An internal loop photo-biodegradation reactor (ILPBR) was used to realize intimately coupled photolysis with biodegradation. The ILPBR was operated with batch experiments following three protocols: photolysis alone (P), biodegradation alone (B), and intimately coupled photolysis and biodegradation (P&B). For P&B, the maximum quinoline removal rate (r _max) increased by 9 %, K _SI increased by 17 %, and the half-maximum-rate concentration (K _S) decreased by 55 %, compared to B; the composite result was a doubling of the quinoline-biodegradation rate for most of the concentration range tested. The degree of mineralization was increased by both forms of photolysis coupled to biodegradation, and the impact was greater for intimate coupling (18 % increase) than sequential coupling (5 %). The benefits of UV photolysis were greater with intimate coupling than with sequential coupling due to parallel transformation by biodegradation and photolysis.     

Algal biomass anaerobic biodegradability

We conducted a series of biodegradation studies using microalgae (Arthrospira maxima and Nannochloropsis sp.) and macroalgae (Gelidium corneum and Cladophora glomerata) to elucidate algal biodegradability in wastewater sludge under anaerobic conditions. Algal biodegradability was evaluated according to ASTM D5210-92. The results indicate that A. maxima biodegraded to a greater extent (70 %) than Nannochloropsis sp. (40 %). The low level of mineralization for Nannochloropsis sp. is due to the presence of high level of lipids (37 %). For macroalgal samples, red algae fiber pulped from G. corneum biodegraded comparably to cellulose controls. However, C. glomerata biodegradation is about 46 %. A sample compositional analysis revealed that it contained about 24.5 % ash, which is directly accountable for an observed low degree of biodegradation. Algal anaerobic biodegradability is important to facilitate sludge digester design and performance evaluation. It is particularly useful when waste residual materials from algal biofuel processing are used for energy production.     

A wood based low-temperature biochar captures NH3-N generated from ruminant urine-N, retaining its bioavailability

Aims

Ammonia (NH₃) can be volatilised from the soil surface following the surface application of nitrogenous fertilisers or ruminant urine deposition. The volatilisation of NH₃ is of agronomic and environmental concern, since NH₃-N is a form of reactive nitrogen. Ammonia adsorption onto biochar has the potential to mitigate NH₃ losses, but to date no studies have examined the potential for reducing NH₃ losses when biochar is present in the soil matrix.

Methods

We used ¹⁵N-enriched urine to examine the effect of incorporating a wood based low-temperature biochar into soil on NH₃ volatilisation. Then, we extracted the urine-treated biochar and compared its potential to act as a plant N source with fresh biochar, while growing ryegrass (Lolium perenne).

Results

The NH₃ volatilisation from ¹⁵N-labelled ruminant urine, applied to soil, was reduced by 45% after incorporating either 15 or 30?t ha^?1 of biochar. When the urine-treated biochar particles were transferred into fresh soil, subsequent plant growth was not affected but the uptake of ¹⁵N in plant tissues increased, indicating that the adsorbed-N was plant available.

Conclusions

Our results show that incorporating biochar into the soil can significantly decrease NH₃ volatilisation from ruminant urine and that the NH₃-N adsorbed onto the biochar is bioavailable. Further studies are now required to assess the temporal dynamics of the N pools involved.     

Microcalorimetry as a diagnostic and analytical tool for the assessment of biodegradation of 2,4-D in a liquid medium and in soil

The biodegradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) byPseudomonas cepacia was assessed by microcalorimetry in a liquid medium and in sterilized soil at 25°C under aerobic conditions. It was found that thermograms of the rate of heat evolved versus time (dQ/dt versust) can be used as a diagnostic tool to identify the timet ₁ required for the primary biodegradation of 2,4-D and the timet _f required for the completion of the biodegradation activity in a liquid medium as well as in soil. Microcalorimetry can also be used as an analytical tool to monitor the progress of 2,4-D consumption during the biodegradation process in a liquid medium and to measure the importance of the soil sorption/desorption of intermediate metabolites. A new concept called bioeffort was defined as the product of the biodegradation time (t) and the biomass concentration (X) at that time. This concept was used to predict either the biomass concentration required or the duration of the primary biodegradation of 2,4-D in soil from the data obtained from a liquid medium.     

Immobilization and characterisation of a lipase from a new source, Bacillus sp. ITP-001

A new source of lipase from Bacillus sp. ITP-001 was immobilized by physical adsorption on the polymer poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) in aqueous solution. The support and immobilized lipase were characterised, compared to the lyophilised lipase, with regard to the specific surface area, adsorption–desorption isotherms, pore volume (Vp) and size (dp) by nitrogen adsorption, differential scanning calorimetry, thermogravimetric analysis, chemical composition analysis, Fourier transform infrared spectroscopy and biochemical properties. The immobilized enzyme displayed a shift in optimum pH towards the acidic side with an optimum at pH 4.0, whereas the optimum pH for the free enzyme was at pH 7.0; the optimum temperature of activity was 80 and 37 °C for the free and immobilized enzyme, respectively. The inactivation rate constant for the immobilized enzyme at 37 °C was 0.0038 h^?1 and the half-life was 182.41 h. The kinetic parameters obtained for the immobilized enzyme gave a Michaelis–Menten constant (K _m) of 49.10 mM and a maximum reaction velocity (V _max) of 205.03 U/g. Furthermore, the reuse of the lipase immobilized by adsorption allowed us to observe that it could be reused for 10 successive cycles, duration of each cycle (1 h), maintaining 33 % of the initial activity.     

Experimental study of 60Co behaviour in Tejo River sediments

The objective of this study was to obtain information on the transfer of radiocobalt in freshwater environments that can be used to predict its environmental distribution. The sediment-water behaviour of ⁶⁰Co in freshwater systems was studied through adsorption and desorption experiments undertaken using sediments and water from Fratel Reservoir in the Tejo River. The suspended sediment concentrations (C_s: 500–2000 mg 1^–1) and Co distribution coefficient (K_d) were inversely related: K_d = 2211–2001 ln [C_s]; K_d ranged from 4000 to 8000 ml g^–1. With a suspended sediment concentration of 1000 mg 1^–1, the ⁶⁰Co concentration remaining in solution (C_t) was given by: C_t = 49.4 e^–0.584t + 46.3 e^–0.014t; where t is the time in days and the half-life periods are 1.2 and 50 days. In a closed system, desorption of ⁶⁰Co could be described by a one-component relation with a half-life of 104 days, and a two component relation (half-life 5 hours and 45 days) in an open system. In river water the ⁶⁰Co was found to be almost 100% in cationic forms, however, in the presence of sediment there was a decrease in the proportion of cationic forms (to 50%), with some anionic forms appearing.     

Bioremediation of naphthalene in water by Sphingomonas paucimobilis using new biodegradable surfactants based on poly (ɛ-caprolactone)

New amphiphilic block surfactants ABA based on a central segment of polycaprolactone with different molecular composition were evaluated in the bioremediation of naphthalene in water by Sphingomonas paucimobilis and compared with sodium dodecyl sulphate as reference surfactant (SDS). Also the biodegradation of the new surfactants by bacteria, S. paucimobilis and a mixture of bacteria (Pseudomonas aureginosa, Bacillus subtilis, Bacillus amyloliquefaciens and Bacillus megaterium) was studied by indirect impedance technique and carbon dioxide determination. All the bacteria biodegraded in solution and micellar phase the central segment of PCL with mineralization rates in the range of 0.024–0.036 mg of CO₂ per day.S. paucimobilis biodegraded naphthalene in the presence of the new surfactants and GC analysis demonstrated that conversion to products started immediately after inoculum. In all the experiments, except for SDS, at 140 h of incubation time, the remaining naphthalene concentration was about 10% of the initial concentration. In contrast, the production of CO₂ was delayed 4–7 days and values around 75% of naphthalene mineralization degree were achieved in three weeks. The addition of PCL-surfactants, in solution and in micellar phase, not interfered in the naphthalene mineralization. These results have shown promising potential of these biodegradable PCL-surfactants in surfactant-enhanced remediation (SER) technology for removing residual organics from contaminated groundwater and soils.