Isolation and characterization of a bacterium which utilizes polyester polyurethane as a sole carbon and nitrogen source

Abstract Various soil samples were screened for the presence of microorganisms which have the ability to degrade polyurethane compounds. Two strains with good polyurethane degrading activity were isolated. The more active strain was tentatively identified as Comamonas acidovorans . This strain could utilize polyester-type polyurethanes but not the polyether-type polyurethanes as sole carbon and nitrogen sources. Adipic acid and diethylene glycol were probably the main degradation products when polyurethane was supplied as a sole carbon and nitrogen source. When ammonium nitrate was used as nitrogen source, only diethylene glycol was detected after growth on polyurethane.     

Microbiological testing of plastics: Ongoing activities of IBRG plastics project group to improve standard test procedures

The early development of standard test procedures for plastics was based primarily upon results of plasticised PVC. Ring tests carried out in the sixties used this material and provided the basis for national and international test specifications. In the meantime a large variety of plastics formulations has been developed which are chemically and structurally different from the formerly used PVC. This has prompted a re-examination of existing test specifications. For this reason the IBRG established a Plastics Working Group in 1984 to study the mechanism of the deterioration of plastics in relation to current standard test protocols.Fifteen laboratories from several European countries participated in a first international ring test (see Appendix). Two polyurethanes — a polyester and a polyether type — were chosen as test materials. A plasticized PVC was included for comparison with earlier interlaboratory experiments. Petri dish tests were carried out for four weeks and biodeterioration was assessed by visual examination and by weight loss. It was concluded that visual assessment as the sole criterion for the biodeterioration of polyurethanes was insufficient and that a test period of four weeks was too short for weight loss determination.In a second ring test with 12 participants, soil burial tests with the same test materials have been started. They will be conducted over a two-year period. Weight loss determinations and tensile tests will be carried out at six-month intervals. Provisional results are presented and are supplemented by joint experiments of some participants to examine the effects of special test parameters on the biodeterioration of plastics.     

Synthesis and characterization of novel blood-compatible soluble chemically cross-linked polyurethanes with excellent mechanical performance for biomedical applications

A controlled cross-linking polymerization system was designed, and soluble chemically cross-linked polyurethane was synthesized using laurylamine, n-octylamine, n-pentylamine, and ethylenediamine chain extenders. The mechanical analysis showed that the polyurethane materials synthesized in this paper have very excellent mechanical properties with a breaking elongation of 1914% and a tensile strength of 4303 N/cm(2). Such good mechanical properties must enable it to have good longevity when used as biomaterials. The polyurethane materials with n-pentylamine and n-octylamine chain extenders show reduced platelet adhesion than that with an ethylenediamine chain extender after sustaining 200 000 times of load cycles, indicating that polyurethanes introduced with an alkyl side chain onto the hard segments keep good antithrombogenic properties after sustaining load cycles. This might be because the hard segments are shielded by the alkyl side chain when the micro-phase-separation structure is destroyed in the repeated deformation of the polyurethane materials. The present investigation reveals that the influence of introducing long alkyl side chains into the backbone of the polyurethane macromolecule has been shown to reduce platelet deposition and to enhance in vitro albumin adsorption. However, in this paper, it has been observed that the polyurethane material introduced with a proper-length alkyl side chain onto the hard segment has the best antithrombogenic properties after the fatigue test.     

Fungal communities associated with degradation of polyester polyurethane in soil

Soil fungal communities involved in the biodegradation of polyester polyurethane (PU) were investigated. PU coupons were buried in two sandy loam soils with different levels of organic carbon: one was acidic (pH 5.5), and the other was more neutral (pH 6.7). After 5 months of burial, the fungal communities on the surface of the PU were compared with the native soil communities using culture-based and molecular techniques. Putative PU-degrading fungi were common in both soils, as <45% of the fungal colonies cleared the colloidal PU dispersion Impranil on solid medium. Denaturing gradient gel electrophoresis showed that fungal communities on the PU were less diverse than in the soil, and only a few species in the PU communities were detectable in the soil, indicating that only a small subset of the soil fungal communities colonized the PU. Soil type influenced the composition of the PU fungal communities. Geomyces pannorum and a Phoma sp. were the dominant species recovered by culturing from the PU buried in the acidic and neutral soils, respectively. Both fungi degraded Impranil and represented >80% of cultivable colonies from each plastic. However, PU was highly susceptible to degradation in both soils, losing up to 95% of its tensile strength. Therefore, different fungi are associated with PU degradation in different soils but the physical process is independent of soil type.     

Symbiosis of Arbuscular Mycorrhizal Fungi and Robinia pseudoacacia L. Improves Root Tensile Strength and Soil Aggregate Stability

Robinia pseudoacacia L. (black locust) is a widely planted tree species on Loess Plateau for revegetation. Due to its symbiosis forming capability with arbuscular mycorrhizal (AM) fungi, we explored the influence of arbuscular mycorrhizal fungi on plant biomass, root morphology, root tensile strength and soil aggregate stability in a pot experiment. We inoculated R. pseudoacacia with/without AM fungus (Rhizophagus irregularis or Glomus versiforme), and measured root colonization, plant growth, root morphological characters, root tensile force and tensile strength, and parameters for soil aggregate stability at twelve weeks after inoculation. AM fungi colonized more than 70% plant root, significantly improved plant growth. Meanwhile, AM fungi elevated root morphological parameters, root tensile force, root tensile strength, Glomalin-related soil protein (GRSP) content in soil, and parameters for soil aggregate stability such as water stable aggregate (WSA), mean weight diameter (MWD) and geometric mean diameter (GMD). Root length was highly correlated with WSA, MWD and GMD, while hyphae length was highly correlated with GRSP content. The improved R. pseudoacacia growth, root tensile strength and soil aggregate stability indicated that AM fungi could accelerate soil fixation and stabilization with R. pseudoacacia, and its function in revegetation on Loess Plateau deserves more attention.     

A demonstration of the effects of substrate screening on the colonisation and decay of cotton textiles in soil burial tests

The screening of a test substrate is a technique which may be employed during soil burial testing of materials (Eggins &Lloyd, 1968). One suggested advantage of such a technique is that only active organisms colonise the material under test. This experiment shows the effects of screening textile samples in soil burial tests, compared with unscreened controls. Two groupes of cotton textile strips were buried in soil and incubated at 25° C. In one group the strips were in direct contact with the soil, in the other group they were screened from direct contact with the soil by a covering of finely woven glass-fibre tape. The strips were removed at intervals for plating-out on agar, and also for tensile testing. Lists of fungal species isolated from the strips were compiled, (Tables 1 and 2) and tensile testing results are shown on the graph. For the purpose of comparing fungal species isolated by this method with those isolated by a less selective technique, an investigation of the soil mycoflora was also made using Warcups' technique. (Table 6).     

Polyhedral oligomeric silsesquioxane (POSS) suppresses enzymatic degradation of PCL-based polyurethanes

In this Article, we studied the enzymatic hydrolytic biodegradation behavior of a novel multiblock thermoplastic polyurethane (TPU) system, which incorporates polyhedral oligomeric silsesquioxane (POSS) into linear biodegradable thermoplastic polyurethanes containing poly(ε-caproactone) (PCL) and polyethylene glycol (PEG) blocks. The biodegradation behavior of POSS-PCL-PEG TPUs was characterized by proton nuclear magnetic resonance spectroscopy ((1)H NMR), differential scanning calorimetry (DSC), tensile tests, scanning electron microscopy (SEM), and wavelength dispersive X-ray spectrometry (WDS) after enduring 22-day accelerated enzymatic hydrolytic degradation tests. POSS incorporation significantly suppressed in vitro enzymatic hydrolytic degradation of PCL-PEG-based multiblock TPUs by a surface passivation mechanism. WDS observations revealed that the covalently bonded POSS moieties developed a near-continuous and robust POSS-layer after initial degradation, which prevented ester bonds of PCL from enzymatic attack, thereby inhibiting further degradation. These striking results provide a new strategy to fabricate the polyester-based biostable thermoplastic polyurethanes (TPUs) of potential use in long-term surgical implants.     

Effects of jet-fuel microbial isolates on a polyurethane foam

Jet-fuel microbial isolates were studied for effects on a polyurethane foam material that has been proposed as a baffling material for use in aircraft fuel tanks. Evidence was found that a polyesterurethane foam gave increased cell counts and oxygen uptake with a bacterial isolate, and extensive matting with fragmentation and decreases in tensile strength of the foam with a fungal isolate. The polyurethane foam was affected by activity of the jet-fuel microbial isolates to an extent that would cause serious microbiological problems in the fuel tanks of jet aircraft.     

Fungal Communities Associated with Degradation of Polyester Polyurethane in Soil

Soil fungal communities involved in the biodegradation of polyester polyurethane (PU) were investigated. PU coupons were buried in two sandy loam soils with different levels of organic carbon: one was acidic (pH 5.5), and the other was more neutral (pH 6.7). After 5 months of burial, the fungal communities on the surface of the PU were compared with the native soil communities using culture-based and molecular techniques. Putative PU-degrading fungi were common in both soils, as <45% of the fungal colonies cleared the colloidal PU dispersion Impranil on solid medium. Denaturing gradient gel electrophoresis showed that fungal communities on the PU were less diverse than in the soil, and only a few species in the PU communities were detectable in the soil, indicating that only a small subset of the soil fungal communities colonized the PU. Soil type influenced the composition of the PU fungal communities. Geomyces pannorum and a Phoma sp. were the dominant species recovered by culturing from the PU buried in the acidic and neutral soils, respectively. Both fungi degraded Impranil and represented >80% of cultivable colonies from each plastic. However, PU was highly susceptible to degradation in both soils, losing up to 95% of its tensile strength. Therefore, different fungi are associated with PU degradation in different soils but the physical process is independent of soil type.     

New insights into polyurethane biodegradation and realistic prospects for the development of a sustainable waste recycling process

Polyurethanes are polymeric plastics that were first used as substitutes for traditional polymers suspected to release volatile organic hazardous substances. The limitless conformations and formulations of polyurethanes enabled their use in a wide variety of applications. Because approximately 10 Mt of polyurethanes is produced each year, environmental concern over their considerable contribution to landfill waste accumulation appeared in the 1990s. To date, no recycling processes allow for the efficient reuse of polyurethane waste due to their high resistance to (a)biotic disturbances. To find alternatives to systematic accumulation or incineration of polyurethanes, a bibliographic analysis was performed on major scientific advances in the polyurethane (bio)degradation field to identify opportunities for the development of new technologies to recondition this material. Until polymers exhibiting oxo- or hydro-biodegradative traits are generated, conventional polyurethanes that are known to be only slightly biodegradable are of great concern. The research focused on polyurethane biodegradation highlights recent attempts to reprocess conventional industrial polyurethanes via microbial or enzymatic degradation. This review describes several wonderful opportunities for the establishment of new processes for polyurethane recycling. Meeting these new challenges could lead to the development of sustainable management processes involving polymer recycling or reuse as environmentally safe options for industries. The ability to upgrade polyurethane wastes to chemical compounds with a higher added value would be especially attractive.     

Extrinsic cell infiltration and revascularization accelerate mechanical deterioration of the patellar tendon after fibroblast necrosis

This study was performed to determine the contribution of extrinsic cell infiltration and revascularization into the patellar tendon in alteration of the mechanical properties of the patellar tendon after intrinsic fibroblast necrosis using 77 rabbits. In Group I, after the patellar tendon underwent the in situ freeze-thaw treatment, a wrapping treatment was performed to inhibit any extrinsic cell infiltration into the tendon. In Group II, the patellar tendon underwent the freeze-thaw treatment without any of the wrapping treatment. In Group III, the patellar tendon underwent the same wrapping treatment but without any freeze-thaw treatment. The cell culture study demonstrated that the in situ freeze-thaw treatment killed from 97 to 100 percent of the cells in the patellar tendon. Histologically, no cells were found in the midsubstance of the patellar tendon in Group I at 1, 3, and 6 weeks. In Group II, a number of cells and some vessels were found scattered in the tendon at 3 and 6 weeks. Mechanically, the elastic modulus and the tensile strength of the patellar tendon of Group II were significantly lower than those of Groups I and III at 3 and 6 weeks. These facts suggest that extrinsic cell infiltration and revascularization from the surrounding tissues accelerate the deterioration of the mechanical properties of the patellar tendon matrix after intrinsic fibroblast necrosis.     

Structure and properties of polyurethanes prepared from triglyceride polyols by ozonolysis

Ozonolysis was used to obtain polyols with terminal primary hydroxyl groups and different functionalities from trilinolein (or triolein), low-saturation canola oil, and soybean oil. The functionality of the model polyol from triolein (trilinolein) was 3.0 and that of soy polyol was 2.5, due to the presence of unreactive saturated fatty acids, while canola gave a polyol with a functionality of 2.8. All polyols exhibited a high tendency to crystallize at room temperature. The resulting waxes had melting points comparable to that of paraffin and very low viscosities in the liquid state. The polyols were cross-linked using 4,4'-methylenebis(phenyl isocyanate) to give polyurethanes. Glass transitions (T(g)) for the model-, canola-, and soy-based polyurethanes were 53, 36, and 22 degrees C, respectively. The about 30 degrees C lower T(g) of the soy-based polyurethane than that of the model polyurethane was the result not only of lower functionality but also of the presence of saturated fatty acids in the former. Polyurethane from the canola polyol had intermediate cross-linking density and properties. These polyurethanes displayed excellent mechanical properties and higher glass transition temperatures compared to polyurethanes from epoxidized and hydroformylated polyols of the same functionality, presumably due to the absence or lower content of dangling chains in the former.     

Local administration of interleukin-1 receptor antagonist inhibits deterioration of mechanical properties of the stress-shielded patellar tendon

We previously found that interleukin (IL)-1beta is over-expressed in the fibroblasts of the stress-shielded patellar tendon using a stress-shielding model [Uchida, H., Tohyama, H., Nagashima, K., Ohba, Y., Matsumoto, H., Toyama, Y., Yasuda, K., 2005. Stress deprivation simultaneously induces over-expression of interleukin-1beta, tumor necrosis factor-alpha, and transforming growth factor-beta in fibroblasts and mechanical deterioration of the tissue in the patellar tendon. Journal of Biomechanics 38(4), 791-798.]. Therefore, IL-1beta may play a role in tendon deterioration in response to stress deprivation. This study was conducted to clarify the effects of local administration of interleukin-1 receptor antagonist (IL-1ra) on the mechanical properties of the stress-shielded patellar tendon as well as the tendon fascicles harvested from it. Twenty-six mature rabbits were equally divided into Groups IL-1ra and PBS after the right patellar tendon underwent the stress-shielding treatment, which completely released the patellar tendon from tension by stretching the flexible wire installed between the patella and the tibial tubercle. In Group IL-1ra, IL-1ra was injected between the patellar tendon and the infra-patellar fat pad. In Group PBS, phosphate-buffered saline was injected in the same manner as IL-1ra. All rabbits were evaluated at 3 weeks after the stress-shielding procedure. The tangent modulus and the tensile strength of the patellar tendons were significantly greater in Group IL-1ra than in Group PBS, while there was no significant difference in the strain at failure between Groups IL-1ra and PBS. Concerning the mechanical properties of the fascicles harvested from the patellar tendon, however, we could not detect any significant differences in the tangent modulus, tensile strength, or strain at failure between Groups IL-1ra and PBS. The present study suggested that IL-1 plays an important role in the deterioration of the mechanical properties of the patellar tendon in response to stress shielding and that IL-1 does not affect the fascicles themselves.     

Changes in sensitivity of Amaranthus retroflexus L seeds to ethylene during preincubation. II. Effects of alternating temperature and burial in soil

Abstract. The effects of diurnally alternating temperatures and of prolonged burial in the soil on germination response of redroot pigweed ( Amaranthus retroflexus L.) seeds to ethylene were investigated. Percentage germination in a 12 h/12 h, 23° C/35° C temperature regime roughly equalled that observed at constant 35° C, and greatly exceeded that observed at 30°C. Preincubation for 61 d in alternating temperatures, which were gradually increased to simulate soil warming in spring, caused little germination in the absence of ethylene, but considerably enhanced sensitivity to ethylene. Seeds kept in soil in the same temperature regime failed to show the response to ethylene, and the soil itself removed ethylene from the soil atmosphere.
After burial in a field plot either over winter or during the summer, seeds had a very low ethylene response threshold (0.01−0.05 cm³ m⁻³) and strong response to ethylene (70–95% germination at 51 cm³ m⁻³ compared to 1–20% without ethylene). Germinability of seeds buried overwinter declined between 10 May (85%) and 24 May (7%), and 90% of those recovered on or after 24 May had a visible rupture in the seed coat. Apparently, germination had begun during burial, but was arrested by unknown causes in an early phase and was followed by seed deterioration.
Although the role of ethylene in germination of buried seeds remains uncertain, the greatly enhanced sensitivity to ethylene observed in pigweed seeds after burial deserves further investigation.     

Fungal susceptibility of polyurethanes

One hundred laboratory-synthesized polyurethanes were tested by a mixed-culture petri dish method for susceptibility to fungus attack. Polyether polyurethanes were moderately to highly resistant to fungal attack, whereas all polyester polyurethanes tested were highly susceptible. The susceptibility of the polyethers was related to the number of adjacent methylene groups in the polymer chain. At least two such groups were required for appreciable attack to occur. The presence of side chains on the diol moiety of the polyurethane reduced susceptibility.     

Effects of burial and soil condition on postharvest mortality of boll Weevils (Coleoptera: Curculionidae) in fallen cotton fruit

Effects of soil condition and burial on boll weevil, Anthonomus grandis grandis Boheman, mortality in fallen cotton, Gossypium hirsutum L., fruit were assessed in this study. During hot weather immediately after summer harvest operations in the Lower Rio Grande Valley of Texas, burial of infested fruit in conventionally tilled field plots permitted significantly greater survival of weevils than in no-tillage plots. Burial of infested squares protected developing weevils from heat and desiccation that cause high mortality on the soil surface during and after harvest in midsummer and late summer. A laboratory assay showed that burial of infested squares resulted in significantly greater weevil mortality in wet than in dry sandy or clay soils. Significantly fewer weevils rose to the soil surface after burial of infested bolls during winter compared with bolls set on the soil surface, a likely result of wetting by winter rainfall. A combination of leaving infested fruit exposed to heat before the onset of cooler winter temperatures and burial by tillage when temperatures begin to cool might be an important tactic for reducing populations of boll weevils that overwinter in cotton fields.     

松属、青冈属乔木侧根的强度在防护林固土护坡作用中的意义

 乔木根系的土壤加强作用是防护林稳定土壤和保护坡面的最有效的机械途径,其中侧根的牵引效应在林地的固土护坡过程中具有重要作用,其潜能与侧根的抗张强度呈正相关关系。本研究构建了侧根抗张强度与其牵引效应的数学模型,对云南山地以云南松林和滇青冈林为代表的松属和青冈属乔木群落进行了分析。结果表明：青冈属和松属乔木侧根的抗张强度分别在40一10MPa和30～5 MPa范围内,量值的高低随侧根直径的增加而降低。两种乔木的侧根在0～60cm的土壤深处有较高的分布密度,由于具有一定的强度,通过它们的牵引效应,侧根使这一深度的根际土层的抗张强度提高了6.85～12.41 kPa。在各个土层,青冈属乔木固土护坡能力明显高于松属,说明松属侧根在浅层土体加固方面具有局限性。     

Rhizomorph Behaviour in Armillaria mellea (Fr.) Quel.: With one Figure in the text: Saprophytic Colonization of Woody Substrates in Soil

Rhizomorphs put out by Armillaria mellea from small woody inoculain glass tubes of moist soil were tested for their ability tocolonize segments of willow shoots, previously killed by autoclavingand then buried for various periods in soil before inoculationwith A. mellea. The degree of saprophytic colonization of thesesubstrate segments by A. mellea was assessed by reburying themin fresh tubes of moist soil, and recording weekly growth incrementsof rhizomorphs put out from them over a period of 5 weeks. Aperiod of previous burial in soil up to 3 weeks was found notto diminish availability of the substrate segments to A. mellea,but with longer periods substrate value for A. mellea progressivelydeclined. Segments of living, green shoots of willow provideda consistently better substrate for A. mellea than did deadsegments, and these living segments maintained their substratevalue over periods (up to 7 weeks) of previous burial in soil.These results are interpreted in terms of competition betweenA. mellea and other soil fungi. In the infection of living tissues,A. mellea benefits from the exclusion of competitors by hostresistance. In the saprophytic colonization of dead tissues,A. mellea has the advantage of its capacity to decompose celluloseand lignin, which are substrates restricted to a minority ofsoil fungi.     

Syntheses and characterization of polymers containing nucleic acid bases

Two different types of polymers containing nucleic acid bases in the backbone or in the pendant groups were prepared. The polymers of the first type were polyureas obtained by the polyaddition reaction of uracil and adenine with hexamethylene diisocyanate (HMD1). The second type that is cationic polyurethanes containing nucleic acid bases in pendant groups, were obtained by the Menschutkin reaction of halogenated derivatives of uracil and adenine with a linear polyurethane containing tertiary nitrogen atoms which was based on HMD1 and N-methyldiethanolamine. Base base interactions were studied for the polymers by ultraviolet (u.r.), optical rotary dispersion (o.r.d.), and nuclear magnetic resonance (n.m.r.) spectra. A relatively high value of hypochromicity, ≈17% was observed for the mixture of the ionic polyurethane with uracil pendant and herring-sperm DNA. Complementary hydrogen bonding interactions were detected for the mixture of the ionic polyurethane with adenine pendant and with uracil pendant. The non-thrombogenic character of the polymers was examined according to the modified Lee White method. The ionic polyurethanes with adenine and uracil pendant exhibited a fairly good anti-clotting properly.     

Seed burial by soil burrowing beetles

Bernhardt, K.-G. 1995. Seed burial by soil burrowing beetles. — Nord J. Bot. 15: 257–260. Copenhagen. ISSN 0107–055X.
This investigation shows the role of soil digging beetles (Carabidae, Heteroceridae) in burial of myxospermous seeds. Field experiments with containers filled with sterilized sand, seeds of different plant species and soil digging beetles, are used. After six months in plots with digging insects seeds were found in deeper soil depths (up to 10 cm soil depth) than seeds in control plots. The study was done with beetles belonging to newly created sandy land. The study shows that beetles can be important for seed dispersal and seed burial and that seeds deep in the soil do not need to be old.