Characterization of Aerobic Bacteria Involved in Degrading Polyethylene Glycol (PEG)-3400 Obtained by Plating and Enrichment Culture Techniques

Polyethylene glycol (PEG) 3400-degrading aerobic bacteria were isolated from tap water and wetland sediments and then characterized. Only one Sphingomonas strain was obtained in enrichment cultures from each inoculum source whereas a total of 15 bacterial strains were isolated on agar plates. Nine of the 15 isolates were confirmed as PEG 3400 degraders. Three of the 9 PEG 3400 degraders were Gram-negative bacteria belonging to the genus Pseudomonas and genus Sphingomonas. The remaining six isolates were Gram-positive bacteria belonging to genera Rhodococcus, Williamsia, Mycobacterium and Bacillus. PEG 3400 was quantified at 194 nm spectrophotometrically and, at the same time, the growth of two Gram-negative (isolates P1 and P7) and five Gram-positive (isolates P2, P3, P4, P5 and P6) PEG 3400-degrading bacteria were assayed in liquid media and on agar plates amended with PEG 3400, and also on Nutrient Agar plates and pure agar plates without PEG 3400 addition. No growth was observed on the pure agar plates for all the tested strains for a period of 31 days. All tested PEG 3400 degraders showed much lower viability in liquid culture than on the corresponding agar plates in the presence of PEG 3400. Two Gram-negative isolates P1 and P7 did not show significant growth advantage over the Gram-positive isolates both on the agar plates and in the liquid medium amended with PEG 3400. Our results suggest that diversity of PEG degrading bacteria is high in the environments and culturing techniques affect the successful isolation of the bacteria responsible for degradation.     

Degradation of poly(3-hydroxybutyrate), PHB,by bacteria and purification of a novel PHB depolymerase fromComamonas sp.

Bacteria capable of growing on poly(3-hydroxybutyrate), PHB, as the sole source of carbon and energy were isolated from various soils, lake water, activated sludge, and air. Although all bacteria utilized a wide variety of monomeric substrates for growth, most of the strains were restricted to degrade PHB and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate, P(3HB-co-3HV). Five strains were also able to decompose a homopolymer of 3-hydroxyvalerate, PHV. Poly(3-hydroxyoctanoate), PHO, was not degraded by any of the isolates. One strain, which was identified asComamonas sp., was selected, and the extracellular depolymerase of this strain was purified from the medium by ammonium sulfate precipitation and by chromatography on DEAE-Sephacel and Butyl-Sepharose 4B. The purified PHB depolymerase was not a glycoprotein. The relative molecular masses of the native enzyme and of the subunits were 45,000 or 44,000, respectively. The purified enzyme hydrolyzed PHB, P(3HB-co-3HV), and—at a very low rate—also PHV. Polyhydroxyalkanoates, PHA, with six or more carbon atoms per monomer or characteristic substrates for lipases were not hydrolyzed. In contrast to the PHB depolymerases ofPseudomonas lemoignei andAlcaligenes faecalis T₁, which are sensitive toward phenylmethylsulfonyl fluoride (PMSF) and which hydrolyze PHB mainly to the dimeric and trimeric esters of 3-hydroxybutyrate, the depolymerase ofComamonas sp. was insensitive toward PMSF and hydrolyzed PHB to monomeric 3-hydroxybutyrate indicating a different mechanism of PHB hydrolysis. Furthermore, the pH optimum of the reaction catalyzed by the depolymerase ofComamonas sp. was in the alkaline range at 9.4.     

Biochemical and Genetic Characterization of an Extracellular Poly(3-Hydroxybutyrate) Depolymerase from Acidovorax Sp. Strain TP4

To determine the properties of enzymes from bacteria that degrade polypropiolactone (PPL), we isolated 13 PPL-degrading bacteria from pond water, river water, and soil. Nine of these strains were identified as Acidovorax sp., three as Variovorax paradoxus, and one as Sphingomonas paucimobilis. All the isolates also degraded poly(3-hydroxybutyrate) (PHB). A PPL-degrading enzyme was purified to electrophoretical homogeneity from one of these bacteria, designated Acidovorax sp. TP4. The purified enzyme also degraded PHB. The molecular weight of the enzyme was estimated as about 50,000. The enzyme activity was inhibited by diisopropylfluorophosphate, dithiothreitol, and Triton X-100. The structural gene of the depolymerase was cloned in Escherichia coli. The nucleotide sequence of the cloned DNA fragment contained an open reading frame (1476 bp) specifying a protein with a deduced molecular weight of 50,961 (491 amino acids). The deduced overall sequence was very similar to that of a PHB depolymerase of Comamonas acidovorans YM1609. From these results it was concluded that the isolated PPL-degrading enzyme belongs to the class of PHB depolymerases. A conserved amino acid sequence, Gly-X₁-Ser-X₂-Gly (lipase box), was found at the N-terminal side of the amino acid sequence. Site-directed mutagenesis of the TP4 enzyme confirmed that ²⁰Ser in the lipase box was essential for the enzyme activity. This is the first report of the isolation a PHB depolymerase from Acidovorax.     

表面活性剂对土壤中石油污染物的解吸

采用4种表面活性剂解吸老化石油污染土壤中的污染物,对其解吸动力学特征及残油组分进行了分析。实验结果表明:在表面活性剂质量浓度相同(0.5 g/L)条件下,土壤中石油污染物解吸率的大小顺序为十二烷基硫酸钠(SDS)曲拉通X-100(TX-100)吐温-80(TW-80)十二烷基苯磺酸钠(SDBS);SDS的解吸率最高,经48 h累积解吸后土壤中石油污染物的解吸率为38.7%;表面活性剂对石油污染物的解吸动力学曲线用Elovich方程拟合,效果最好,相关系数为0.970 2~0.995 6;非离子表面活性剂(TX-100、TW-80)对石油污染物中饱和烃组分的解吸率优于阴离子表面活性剂(SDS、SDBS),而对芳香烃组分的解吸率不如阴离子表面活性剂。     

Remediation of DDT‐contaminated soil using optimized mixtures of surfactants and a mixing system

Soil contaminated with persistent pesticides, such as DDT, poses a serious risk to humans and to wildlife. A surfactant‐aided soil‐washing technique was studied as an alternative method for remediation of DDT‐contaminated soil. An ex situ soil washing method was investigated using nonionic and anionic surfactants due to the clayey structure of the contaminated soil. A mixture of 1 percent nonionic surfactant (Brij 35) and 1 percent anionic surfactant (SDBS) removed more than 50 percent of DDT from soil in a flow‐through system, whereas individual surfactants or other combinations of the surfactants had a lower removal efficiency. The soil‐washing technique was improved using a mixing system. The mixture of surfactants was optimized in the mixing system, and the combination of 2 percent Brij 35 and 0.1 percent SDBS was found to be optimum, removing 70 to 80 percent of DDT. Prewashing of the soil with tap water decreased the adsorption of surfactants to soil particles by 30 to 40 percent, and postwashing recovered 90 percent of the surfactants. © 2010 Wiley Periodicals, Inc.     

Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in compost

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or copolymers with 10% [P(3HB-co-10%3HV)] and 20% [P(3HB-co-20%3HV)] 3-hydroxyvaleric acid was studied in small household compost heaps. Degradation was measured through loss of weight (surface erosion) and changes in molecular weight and mechanical strength. It was concluded, on the basis of weight loss and loss of mechanical properties, that P(3HB) and P(3HB-co-3HV) plastics were degraded in compost by the action of microorganisms. No decrease inM _w could be detected during the degradation process. The P(3HB-co-20%3HV) copolymer was degraded much faster than the homopolymer and P(3HB-co-10%3HV). One hundred nine microbial strains capable of degrading the polymersin vitro were isolated from the samples used in the biodegradation studies, as well as from two other composts, and identified. They consisted of 61 Gram-negative bacteria (e.g.,Acidovorax facilis), 10 Gram-positive bacteria (mainlyBacillus megaterium), 35Streptomyces strains, and 3 molds.     

Bacteria Degrading PCBs and CBs Isolated from Long-Term PCB Contaminated Soil

Bacteria able to degrade polychlorinated biphenyls (PCBs) and chlorobenzoic acids (CBs) were isolated from soil that had been contaminated with PCBs for 15–30 years. Contaminated soil in which PCB content ranged between 10–470 mg/kg was naturally vegetated with different plants including ash (Fraxinus excelsior), birch (Betula pendula), black locust (Robinia pseudoacacia), Austrian pine (Pinus nigra) and goat willow (Salix caprea) trees as well as a variety of grasses and forbs. Bacteria able to use biphenyl as a sole source of carbon and energy were found in the root zone of all plants, but occurred in the largest numbers beneath pine and black locust. Bacteria able to degrade chlorobenzoic acids were isolated from the same location contaminated with PCBs. Strains that were taxonomically identified by 16S rDNA as Pandoraea were able to use 2-CB, 3-CB, 2,3-CB, 2,5-CB as sole carbon sources, and the strain Arthrobacter utilised 4-CB.     

Polymer Mineralization in Soils: Effects of Cold Storage on Microbial Populations and Biodegradation Potential

Soil retrieval, processing and storage procedures can have a profound effect on soil microorganisms. In particular, changes in soil microbial populations may adversely affect the biological activity of a soil and drastically alter the soil's potential to mineralize added substrates. The effects of cold storage on the biodegradation of a series of test polymers was investigated using two soils—a synthetic soil mix (SM-L8) and a field soil (Bridgehampton silt loam) from Rhode Island (RI-1). Biodegradation tests were conducted using freshly prepared/collected soil and again following storage at 4°C for 3 to 8 months. Prior to each biodegradation test, the soils were incubated at 60% water-holding capacity (WHC) and 25°C to rejuvenate the microbial populations; the soils were incubated for periods of 48 h (freshly collected soil) or 25 days (soils stored at 4°C). Soil microbial populations were assessed by enumerating different segments of the population on agar plates containing different selective media. Mineralization of the test polymers (cellulose, poly-3-hydroxybutyrate, and starch acetate, d.s. 1.5) was monitored using standard respirometric techniques. Our results demonstrated that cold storage had a generally negative effect on the soil microbial populations themselves but that its effect on the capacity of the soil microorganisms to degrade the test polymers varied between soils and polymer type. Whereas cold storage resulted in dramatic shifts in the community structure of the soil microbial populations, substantial restoration of these populations was possible by first conditioning the soils at 60% WHC and ambient temperatures for 25 days. Likewise, although the effects of cold storage on polymer mineralization varied with the test polymer and soil, these effects could be largely offset by including an initial 25-day stabilization period in the test.     

Microbial Degradation of UV-Pretreated Low-Density Polyethylene Films by Novel Polyethylene-Degrading Bacteria Isolated from Plastic-Dump Soil

Eleven effective low-density polyethylene (LDPE)-degrading bacterial strains were isolated and identified from landfill soil containing large amounts of plastic materials. The isolates belonged to 8 genera, and included Pseudomonas (areroginosa and putida), Sphingobacterium (moltivorum), Delftia (tsuruhatansis), Stentrophomonas (humi and maltophilia), Ochrobacterum (oryzeae and humi), Micrococcus (luteus), Acinetobacter (pitti), and Citrobacter (amalonaticus). Abiotic degradation of LDPE films by artificial and natural ultraviolet (UV)-exposure was analyzed by FT-IR spectroscopy. LDPE films treated with UV-radiation were also inoculated with the isolates and biofilm production and LDPE degradation were measured. Surface changes to the LDPE induced by bacterial biofilm formation were visualized by Scanning Electron Microscopy. The most active bacterial isolate, IRN19, was able to degrade polyethylene film by 26.8?±?3.04% gravimetric weight over 4 weeks. Analysis of 16S rRNA sequence of this isolate revealed 96.97% similarity in sequence to Acinetobacter pitti, which has not previously been identified as a polyethylene-degrading bacterium. Also, most the effective biofilm forming isolate, IRN11, displayed the highest cell mass production (6.29?±?0.06 log cfu/cm²) after growth on LDPE films, showed 98.74% similarity to Sphingobacterium moltivourum.     

Biodegradation of Poly(vinyl alcohol) and Bacterial Cellulose Composites by <Emphasis Type="Italic">Aspergillus niger</Emphasis>

The ability of fungal strains to attack a composite material obtained from poly(vinyl alcohol) (PVA) and bacterial cellulose (BC) is investigated. The fungal strain tested was Aspergillus niger. This fungal strain was able to change not only the polymer surface from smoother to rougher, but also to disrupt the polymer. The degradation results were confirmed by visual observations, scanning electron microscopy (SEM) analyses, X-ray diffraction analyses and FTIR spectra of the film samples. SEM micrographs confirmed the growth of fungi on the composite film surface. The degree of microbial degradation depends on culture medium and on composition of polymeric materials, especially on PVA content. The biodegradation process is accelerated by the presence of glucose in the culture medium as an easily available carbon source.     

Production of Polyhydroxyalkanoates from Fatty Wastes

The production of polyesters from triglyceride containing substrates was investigated. A first filter step based on lipase activity was followed and those bacteria potentially able to degrade oils or animal fats were further tested for their polymer accumulation properties, selected and kept for further studies. In a second step, bacteria were directly grown on animal fats and/or vegetable oils, and polyhydroxyalkanoates (PHAs) accumulation was verified under appropriate incubation conditions. Each substrate, whether of animal or vegetable derivation, supported the growth of a number of the newly isolated strains and among those, some strains were also found to produce reasonably high amounts of PHA. The repeat-unit composition of the polyesters was determined by gas chromatography (GC) analysis of the ?-hydroxyalkanoate methyl esters from the hydrolyzed polymer and some class of co-polymers were also detected. These properties, coupled with the ability of some of the selected isolates to grow and produce lipases on a minimal medium, could be considered as promising in view of possible industrial applications. The overall results indicate that PHAs could be produced from waste containing considerable amounts of fat, oil and grease (FOG), that generally need to be treated for their disposal.     

Biodegradation of Polycyclic Aromatic Hydrocarbons by Exopolymers Synthesized by Moderately Halophilic Bacteria: Chemical Composition and Functional Properties

Three strains of halophilic bioemulsifier-producing bacteria; Bacillus sp. 2BSG-PDA-16, Bacillus sp. DV2-37 and Bacillus licheniformis ABRII6 were isolated from crude oil polluted water samples. Characteristics of exopolymers produced by these strains in media supplemented with various hydrocarbons instead of glucose were studied. Yield production, chemical composition, emulsifying, rheological and flocculating properties of exopolymers varied according to the strain and the carbon source. The highest amount of exopolymers synthesized by Bacillus sp. 2BSG-PDA-16, Bacillus sp. DV2-37 and B. licheniformis ABRII6 was 11, 18.5 and 12.4 g/l, respectively from media amended with glucose, while the most active emulsifiers were those obtained from media added with crude oil. Furthermore, all exopolymers produced were capable of emulsifying crude oil more efficiently than the three chemical surfactants tested as control (Tween 20, Tween 80 and Triton X-100). Respect to chemical composition, exopolymers produced on hydrocarbons always have lower content of carbohydrates and proteins than exopolymers produced in medium amended with glucose, however they showed higher amounts of uronic acids, sulfates and acetyl residues. The rheological study suggested that the exopolymers have characteristics of the pseudoplastic fluids. Efficiency of bacterial strains to remove PAH seems to agree with their potential applicability in oil bioremediation technology.     

Lysinibacillus sphaericus and Geobacillus sp Biodegradation of Petroleum Hydrocarbons and Biosurfactant Production

Petroleum oil is a major driver of worldwide economic activity, but it has also created contamination problems during the storage and refining process. Also, unconventional resources are natural resources, which require greater than industry‐standard levels of technology or investment to exploit. In the case of unconventional hydrocarbon resources, additional technology, energy, and capital have to be applied to extract the gas or oil. Bioremediation of petroleum spill is considered of great importance due to the contaminating effects on human health and the environment. For this reason, it is important to reduce total petroleum hydrocarbons (TPH) in contaminated soil. In addition, biosurfactant production is a desirable property of hydrocarbon‐degrading microorganisms. Seven strains belonging to Lysinibacillus sphaericus and Geobacillus sp were selected to evaluate their ability to biodegrade TPH in the presence of toxic metals, their potential to produce biosurfactants, and their ability to improve the biodegradation rate. The seven bacterial strains examined in this study were able to utilize crude petroleum‐oil hydrocarbons as the sole source of carbon and energy. In addition, their ability to degrade crude oil was not affected by the presence of toxic metals such as chromium and arsenic. At the same time, the strains were able to reduce toxic metals concentration through biosorption processes. Biosurfactant production was determined using the drop‐collapsed method for all strains, and they were characterized as both anionic and cationic biosurfactants. Biosurfactants showed an increase in biodegradation efficiency both in liquid minimal salt medium and landfarming treatments. The final results in field tests showed an efficiency of 93 percent reduction in crude oil concentration by the selected consortium compared to soil without consortium. The authors propose L. sphaericus and Geobacillus sp consortium as an optimum treatment for contaminated soils. In addition, production of biosurfactants could have an application in the extraction of crude oil from unconventional hydrocarbon resources. © 2014 Wiley Periodicals, Inc.     

Comparative degradation between heavy and light crude oil mediated by nitrogen‐induced cell‐surface hydrophobicity

A bacterial strain UKMP‐10M2 isolated from a Malaysian petroleum refinery was able to degrade 84% of heavy Khafji sour crude and 68% of light Tapis sweet crude within seven days. Analysis of gas chromatography‐flame ionization detector chromatograms show the strain UKMP‐10M2 degraded up to 90% pristane and 50% phytane in heavy crude, but significantly lower pristane (50%) and phytane (30%) were degraded from the light crude. A mixture of aliphatic hexadecane and three‐ring phenanthrene better supported the growth of isolate UKMP‐10M2 compared to using phenanthrene alone, suggesting cometabolism influenced how crude oil with different individual hydrocarbon contents affected the degradation. Peptone as the source of nitrogen increases the emulsifying index in UKMP‐10M2 exposed to heavy Khafji sour crude 20% higher than in light Tapis sweet crude. However, BATH assay showed the same nitrogen source increases bacterial cell surface hydrophobicity of UKMP‐10M2 up to 14% higher in light Tapis crude oil compared to heavy Khafji. This study suggest the nitrogen source plays a decisive role in elevating UKMP‐10M2 bacterial cells hydrophobicity, and in correlation with types of crude oil. Phylogenetic tree analysis based on 16S rDNA sequence results identified the strain to be Rhodococcus ruber.     

Microbial Poly(L-Lactide)-Degrading Enzyme Induced by Amino Acids, Peptides, and Poly(L-Amino Acids)

Poly(L-lactide)(PLA)-degrading activities of a fungus, Tritirachium album, and two strains of actinomycetes,Lentzea waywayandensis and Amycolatopsis orientalis, were inducible by some proteins (poly-L-amino acid), peptides and amino acids. Extracellular PLA-degrading activity of the culture filtrates was detected when these strains grew in liquid basal medium containing 0.1% (w/v) of (poly-L-amino acids), peptides or amino acids as the enzyme inducer. In addition to PLA-degrading activity, succinyl-(L-alanyl-L-alanyl-L-alanine)-p-nitroanilide (Suc-(Ala)₃-pNA)-degrading activity was observed, implying that the enzymes produced were protease-type. The enzyme activities produced varied between different strains and different inducers. Silk fibroin was the best inducer for A. orientalis and that elastin was the best inducer for L. waywayandensis and T. album.     

Microbial Enzymes Involved in Polyurethane Biodegradation: A Review

Plastics are present in a lot of aspects of everyday life. They are very versatile and resistant to microbial attack. Polyurethanes are used in several industries and are divided in polyester and polyether polyurethanes and there are different types among them. Despite their microbial resistance, they are susceptible to the attack of fungi and bacteria but the mechanism to elucidate its biodegradation are unknown. There are reports from bacteria and fungi that are capable of degrading polyurethane but the studies about the enzymes that attack the plastic are focused on bacterial enzymes only. The enzymes reported are of type esterase and protease mainly since these enzymes are very unspecific and can recognize some regions in the polyurethane molecule and hydrolyze it. Fungal enzymes have been studied prior the 1990s decade but recently, some authors report the use of filamentous fungi to degrade polyurethane and also report some characteristics of the enzymes involved in it. This review approaches polyurethane biodegradation by focusing on the enzymes reported to date.     

The efficacy of an oxidation pond in mineralizing some industrial waste products with special reference to fluorene degradation: a case study

The efficacy of the oxidation pond on the outskirts of the 10th of Ramadan, the main industrial city, in Egypt was examined. Samples of wastewater collected from the inlet and the outlet were screened for some priority pollutants. Acenaphthene and fluorene were the most frequently detected polycyclic aromatic hydrocarbons, while dimethyl phthalate was the most frequently detected phthalate ester. The spectrum of pollutants, their concentrations and frequencies were similar in the inlet and the outlet, indicating an inferior mineralization capability of the pond. Several degradative bacterial strains were isolated from the pond and grown on M56 minimal media supplemented with different pollutants as the carbon source. The efficacy of pure and mixed cultures to break down fluorene, the most frequently detected pollutant was examined. Fluorene degradation was fast in the first 10 days, then followed by a slow phase. Mixed culture had a higher rate of fluorene degradation in comparison to pure cultures. High performance liquid chromatography analysis of fluorene degradation showed three degradative metabolites. But GC/MS analysis detected one compound, identified as acetamide. The present work has indicated the poor efficacy of the pond. Lack of primary treatment of industrial effluent at factory level, coupled with shock loads of toxicants that may damage the microorganisms and their degradative capabilities are presumably main factors behind such inferior performance. Moreover, the type of pollutants discharged into the pond tend to fluctuate and change depending on the rate from the factories discharge and work shifts. Such irregular feeding of persistent pollutants may have led to a wash out of specialized strains of bacteria capable to degrade such persistent pollutants.     

Infrared and nuclear magnetic resonance evidence of degradation in thermoplastics based on forest products

The degradation of lignin-(1-phenylethylene) graft copolymers (lignin-styrene graft copolymers) by white rot basidiomycete fungi was followed by monitoring aromatic absorption bands by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The FTIR of the graft copolymers shows a series of characteristic absorbance peaks from multi-substituted aromatic rings and a strong poly(1-phenylethylene) (polystyrene) absorbance peak from monosubstituted aromatic rings. Subtraction of copolymer spectra taken before incubation from spectra taken after 50 days of incubation with the four tested fungi shows the loss of functional groups from the copolymer. NMR spectra also show reduction of aromatic ring resonances from the copolymer and incorporation of peaks from fungi as a result of incubation with fungi. The biodegradation tests were run on lignin-(1-phenylethylene) graft copolymers which contained 10.3, 32.2, and 50.4% of lignin. The polymer samples were incubated with the white rot fungiPleurotus ostreatus, Phanerochaete chrysosporium, andTrametes versicolor, and the brown rot fungusGleophyllum trabeum. White rot fungi degraded the plastic samples at a rate that increased with increasing lignin content in the copolymer sample. Both poly(1-phenylethylene) and lignin components of the copolymer were readily degraded. Observation by scanning electron microscopy of incubated copolymers showed a deterioration of the plastic surface. The brown rot fungus did not affect any of these plastics, nor did any of the fungi degrade pure poly(1-phenylethylene).Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.     

Isolation of a fungus from denitrifying activated sludge that degrades highly chlorinated dioxins

 This article reports the potential of denitrifying activated sludge to degrade highly chlorinated dioxins, especially from a (landfill) leacheate treatment plant in Japan, and the isolation from this denitrifying activated sludge of a microorganism able to degrade highly chlorinated dioxins. Using a 700-ml bioreactor, denitrifying activated sludge was cultivated under denitrifying conditions by adding 2.0 ng of a mixture of 4- to 8-chlorinated dioxins from fly ash. The dioxin contents of the sample, effluent, and medium before and after cultivation were measured by gas chromatography–mass spectrometry (GC–MS). After 7 days cultivation, about 90% of added dioxins were lost (average percentage of isomer depletion). A dioxin-degrading microorganism was isolated from the activated sludge. Lignin was added to the medium as a color indicator of aromatic compound degradation, and the lignin-decolorizing microorganisms in the denitrifying activated sludge were screened. Some strains were isolated, and one major isolated fungus, strain 622, decolorized lignin effectively. Strain 622 was identified as an Acremonium sp. from its morphological characteristics. It could decolorize lignin by 24% under paraffin-sealed anaerobic conditions. After the cultivation of strain 622 with a 2 ng/ml mixture of 4- to 8-chlorinated dioxins for 1 day, 82% (average for individual isomers) of the added 4- to 8-chlorinated dioxins had been degraded. Added octachlorodibenzo-p-dioxin (OCDD, 100 ng) was degraded under aerobic conditions after 8 h of incubation. During this process, heptachlorodibenzo-p-dioxin was produced and appeared to be a degradation product of OCDD. 1- or 2-hydroxydibenzo-p-dioxin from OCDD was also identified as the degradation product by GC–MS. These results indicated that OCDD was degraded to the nonchlorinated dibenzo-p-dioxins through dechlorination by Acremonium sp. strain 622. Received: October 12, 2001 / Accepted: March 11, 2002     

N-长链碳酰基-L-苯丙氨酸单甲基聚乙二醇酯的合成及其性质研究

以L-苯丙氨酸、长链烷基（C₁₂/C₁₄/C₁₆/C₁₈）酰氯和聚乙二醇单甲醚（MPEG,M_n=350,550,750,1 000 g/mol）为原料,合成了一系列新型非离子型表面活性剂N-长链碳酰基-L-苯丙氨酸单甲基聚乙二醇酯（Rn-L-MPEG）,系统研究了表面张力、界面张力和土壤吸附性与其结构之间的关系。结果表明：随着MPEG分子量的增大,Rn-L-MPEG的表面张力逐渐下降;随着酰氯中烷基链的增长,Rn-L-MPEG的表面张力呈现增大趋势,系列表面活性剂中R12-L-MPEG1000具有最低的表面张力28.11 mN/m;Rn-L-MPEG的界面张力随分子结构变化的规律同表面张力;随着MPEG分子量的增大,Rn-L-MPEG的饱和吸附量逐渐增大,随着酰氯中烷基链的增长,Rn-L-MPEG的饱和吸附量呈现下降趋势。