Enzymatic degradation of poly([R,S] β-hydroxybutyrate)

The synthetic analogue of a bacterially produced polyester, poly(-hydroxybutyrate) (PHB) was synthesized from racemic -butyrolactone using anin situ trimethyl aluminum-water catalyst. The polymer was fractionated into samples differing in molecular weight and isotactic diad content. The latter was closely related to degree of crystallinity. The biodegradation of these fractions were examined by monitoring mass loss over time in the presence of anAlcaligenes faecalis T1 extracellular bacterial poly(-hydroxybutyrate) depolymerase. The fraction with high isotactic diad tacticity content showed little or no degradation over a 50 hour incubation period, whereas the fraction of intermediate isotactic diad content degraded in a continuous steady fashion at a rate that was less than that for bacterial PHB. The low isotactic diad fraction underwent a rapid initial degradation, followed by no further mass loss. The presence of stereoblocks in the polymer structure of the various fractions was an influence on the degree of susceptibility towards degradation and is related to sample crystallinity.     

Crystallization behavior of predominantly syndiotactic poly(β-hydroxybutyrate)

Predominantly syndiotactic poly(-hydroxybutyrate), syn-PHB, of variable syndioregularity (syndyad fractions 0.59, 0.62, 0.64, and 0.71) and molecular weight was prepared by the dibutyltin dimethoxide catalyzed ring opening of racemic-butyrolactone (BL). The crystallization behavior of the syn-PHB polymers was investigated by DSC and X-ray diffraction analyses. DSC of films after melting and annealing showed at least one, and often two distinct melting transitions occuring over a broad (often 40°C) temperature range. These results indicate that syn-PHB chain segments of variable syndioregularity form crystalline regions with very different thermodynamic stabilities. Maximum degrees of crystallinity for melt annealed 0.64- and 0.71-syn-PHB was observed at an annealing temperature (T _c ) of 30°C. AtT _c values at 45°C and higher, crystallization of relatively lower syndioregular chain segments was apparently excluded to variable degrees dependent onT _c and sample syndiotactic dyad content. After crystallization of syn-PHB samples at elevated temperatures, ambient temperature annealing resulted in an observed lower temperature melting transition at 50°C. This result showed little to no dependence on syn-PHB syndio-regularity andT _c . Both solution precipitated 0.62-syn-PHB and 0.71-syn-PHB have WAXS patterns with poorly resolved crystalline reflections superimposed on amorphous haloes indicating low levels of crystallinity (17% and 25%, respectively) and poorly formed crystals. Isothermal crystallization monitored by DSC showed that the syn- and natural origin PHB showed fastest crystallization rates at temperatures between 50°C and 70°C and 60°C and 90°C, respectively. From the dependence of the higher melting transition onT _c it was determined that the equilibrium melting temperatures for 0.62-syn-PHB (M _n =83,700 g/mol) and a 0.64-syn-PHB (M _n =11,900 g/mol) were 157 and 154°C, respectively. An Avrami analysis of syn-PHB yielded results similar to that found for natural origin PHB indicating that crystal growth occurs by a two-dimensional mechanism.Guest Editor: Dr. Graham Swift, Rohm & Haas.     

Air Pollution Zones and Harmful Pollution Levels of Alkaline Dust for Plants

For characterisation of landscapes in north-eastern Estoniaaffected by alkaline oil shale fly ash and cement dust the zonation-method based on average annual (C _y) and short-termconcentrations of pollutants in the air was used, as well as on deposition loads of dust and Ca²⁺. In the overground layer of atmosphere the zones with different air pollution loads were distinguished. A comparative analysis of pollution zones characteristics and biomonitoring data revealed that for sensitive lichen the dangerous level of alkaline dust in the air, introducingthe degradation of Sphagnum sp. at the level of C _y of dust 10–20 g m^-3 and at 0.5–1 hr maximums 100–150 g m^-3. For Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) this limited concentration (decline of growth parameters) of cement dust is correspondingly following: 30–50 g m^-3 and 150–500 g m^-3, in case of fly ash the limit level of C _y amounting 100 g m^-3. Daily deposition load of Ca²⁺ should not exceed approximately 4.5–15 mg m^-2 for lichen; for conifers the harmful pollution load is higher – >22 mg m^-2.     

In situ bioremediation of a hydrocarbon polluted site with cyclodextrin as a coadjuvant to increase bioavailability

Bioavailability is one main factor that influences the extent of biodegradation of hydrocarbons. They are very poorly soluble in water and easily adsorbed to clay or humus fractions, so they pass very slowly to the aqueous phase where they are metabolised by microorganisms. Cyclodextrins are natural compounds that form soluble inclusion complexes with hydrophobic molecules and increase degradation rate of hydrocarbons in vitro. In the perspective of an in situ application, we previously checked that -cyclodextrin does not increase eluviation of hydrocarbons through the soil and consequently does not increase the risk of groundwater pollution. The results of an in situ application of -cyclodextrin for bioremediation of a hydrocarbon polluted site are presented. We stated that the combination of bioaugmentation and enhanced bioavailability due to -cyclodextrin was effective for a full degradation.     

Effect of Crystalline and Amorphous Structures on Biodegradability of Poly(Tetramethylene Succinate)

The effect of orientation in the amorphous and crystalline regions on the biodegradability of PTMS [poly(tetramethylene succinate)] was studied using the amorphous orientation function, birefringence, and crystallinity. The crystalline and amorphous intrinsic lateral sonic moduli, E _t,c ⁰ and E _t,am ⁰ , were 2.61 × 10³ and 0.41 × 10³ MPa, respectively. Using the data on birefringence, crystalline and amorphous orientation function (f and f _am), crystallinity, and sonic modulus of the oriented PTMS fibers, the intrinsic birefringence of the crystalline ( _c ⁰ ) and amorphous ( _am ⁰ ) regions were evaluated to be 0.0561 and 0.0634, respectively. The biodegradabilities of oriented PTMS films were reduced as the elongation increased, i.e., the amorphous orientation increased. At low elongation (100 and 150%), however, biodegradabilities remained unchanged when the degradation test was performed in activated sludge, which was attributed to the amorphous orientation occurring even at 100% elongation, though the amorphous orientation direction was perpendicular to the fiber axis.     

Species Composition of Freshwater Invertebrates in Relation to Chemical and Physical Factors in High Mountains in Soutwestern Norway

The composition of benthic invertebrates was investigated in three Norwegian alpine watersheds during the period 1991–1997. The watersheds represented an environmental gradient in chemical factors. The Kvenna watershed was relatively well buffered, Lake Øvre Neådalsvatn was poorly buffered, but receives low inputs of atmospheric pollution while Lake Stavsvatn has low buffering capacity and receives larger inputs of acidifying components. Qualitative samples were taken in the inlet rivers, lake littoral zone, lake outlet and in the outlet rivers of the lakes for analyses of species composition. In Ø. Neådalsvatn the water chemical data showed strong seasonal variations with waters of low ionic content during snowmelt and summer, while increased ion concentrations build up during winter. The time of ice break and/or water temperature rise during the growing season affected the life cycle of Siphlonurus lacustris and Parameletus chelifer. Even small changes in pH or ANC seemed to have a strong effect on Baetis rhodani. In the Kvenna watershed eight very sensitive species were found at sites with pH 6.5, Ca 1.2 mg L^-1 and LAl < 10 eq L^-1. Only two highly sensitive species, B. rhodani and Capnia sp. were recorded when pH was 6, concentration of calcium 0.8 mg L^-1 and low labile aluminium < 10 eq L^-1. None of the highly sensitive species occurred in Stavsvatn, a formerly acidified area, where LAl concentrations ranged between 25–40 eq L^-1. Low ionic content and elevated concentrations of labile aluminium are suggested to exclude sensitive invertebrates in alpine lakes. Synergistic effects of dilute water and harsh climate are assumed to increase sensitivity of invertebrates to acid water. Global warming will result in higher precipitation and more snow in the west Norwegian alpine area. This will shorten the growing season, increase the amount of dilute water and consequently threaten invertebrate species living close to their tolerance limits.     

Synthesis and biodegradation of poly(γ-butyrolactone-co-l-lactide)

Biodegradable polyesters were synthesized by ring-opening copolymerization of -butyrolactone (BL) and its derivatives withl-lactide (LLA). Although tetraphenyl tin was the main catalyst used, other organometallic catalysts were used as well.¹H and¹³C NMR spectra showed that poly(BL-co-LLA)s were statistical and that their number-average molecular weights were as high as 7×10⁴. The maximum BL content obtained from copolymerization BL/LLA was around 17%. TheT _m andT _g values of the copolymers showed a gradual depression with an increase in BL content. NoT _m was obtained for the copolymers containing more than 13 mol% BL. The biodegradability of the copolyesters was evaluated by enzymatic hydrolysis and nonenzymatic hydrolysis tests. The enzymatic hydrolysis was carried out at 37°C for 24 h using lipases fromRhizopus arrhizus andR. delemar. Hydrolyses by both lipases showed that an increase in BL content of the copolymer resulted in enhanced biodegradability. Nonenzymatic accelerated hydrolysis of copolymers at 70°C was found to increase proportionally to their exposure time. The hydrolysis rate of these copolymers was considerably faster than that of PLLA. The higher hydrolyzability was recorded for the BL-rich copolymers. The copolymerization of -methyl--butyrolactone (MBL) or -ethyl--butyrolactone (EBL) with LLA resulted in relatively LA-rich copolymers.     

Investigation of the Aerobic Biodegradability of Several Types of Cyclodextrins in a Laboratory-Controlled Composting Test

The biodegradation of several types of cyclodextrins (CDs) under laboratory-controlled composting conditions was investigated. CDs are used in a broad range of applications in food, pharmaceutical, medical, chemical, and textile industries because of their specific chemical characteristics related to their hydrophobic interior and hydrophilic exterior. The three naturally occurring cyclodextrins -CD, -CD, and -CD proved to be completely and readily biodegradable. Chemical modification of these basic compounds can have a major impact on the biodegradation rate and final biodegradation percentage. Fully acetylated -CD and -CD were found to be nonbiodegradable during 45 days of composting. Reducing the degree of acetylation had a positive effect on the biodegradation. Complete biodegradation was obtained for partially acetylated -CD with a degree of substitution (DS) of 7. The methylation (DS = 13) of -CD resulted in an undegradable compound during the 47 days composting, while (2-hydroxy)propyl--CD reached a plateau in biodegradation at a percentage of 20%. The incorporation of the antimicrobial agents imazalil and allyl-isothiocyanate into -CD had no negative impact on biodegradation, which makes these antimicrobial agents/CD complexes suitable for incorporation into biodegradable active packaging.     

Decomposition reactions of epoxy resin and polyetheretherketone resin in sub- and supercritical water

Epoxy resin and polyetheretherketone (PEEK) resin were decomposed into their monomers such as phenol, cresols, and their analogues by thermal treatment in sub- and supercritical water in a 10-ml tubing bomb reactor. The addition of basic compounds such as Na₂CO₃ was effective in promoting the decomposition reaction of the resins. In the reaction of epoxy resin, the yield of identified products reached 10% for the reaction at 703K over 1h. In the reaction of PEEK resin, the total yield of phenol and dibenzofuran reached 88% for the reaction at 703K over 3h. Chemical participation of water in the decomposition reaction was confirmed by the reaction of dinaphthylether.     

Biodegradability: An assessment of commercial polymers according to the Canadian method for anaerobic conditions

The degradation of several biodegradable polymers was measured as a result of exposure to an anaerobic medium. The polymers investigated included materials based upon polylactic acid, polylactone, and poly(hydroxy butyrate/valerate) as well as those incorporating starch-based materials. The degradation was monitored by methane and carbon dioxide evolution. In addition, the physical and chemical changes were noted as a result of exposure. These measurements included changes in mass, dimension, and molecular weight. FTIR, UV-vis, proton, and¹³C NMR spectra were also recorded prior to and after exposure. The results clearly indicated that several biological and chemical degradation processes were occurring with the biodegradable polymers studied.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Issued as NRCC No. 37549.     

Distribution of Poly(β-propiolactone) Aerobic Degrading Microorganisms in Different Environments

The distribution of degading microorganisms of high molecular weight poly(-propiolactone) (PPL), whose individual structural units are similar to those of poly(-hydroxybutyrate) (PHB) and poly(€-caprolactone) (PCL), was examined. Despite the fact that PPL is a chemosynthetic polymer, many kinds of PPL-degrading microorganisms were found to be distributed as resident populations widely in natural environments. A total of 77 strains of PPL-degrading microorganisms was isolated. From standard physiological and biochemical tests, at least 41 strains were referred to as Bacillus species. Microbial degradation of fibrous PPL proceeded rapidly in some enrichment cultures but was not as complete as that of PHB. Most of the isolated PPL-degrading microorganisms were determined to be PCL degraders and/or PHB degraders. Therefore, it can be assumed that mostly PPL is recognized by the microorganisms as PHB or another natural substrate of the same type as which PCL is regarded. Microbial degradation of PPL was confirmed by some Bacillus strains from type culture collections. The similarity of microbial degradation between PPL and PCL was found to be very close.     

What substances or objects should be recycled? The recycling legislative experience in Taiwan

The legislative framework of waste management in Taiwan has never been efficient, mainly due to unclear definitions and regulations. In 2002, this system was split into two parts by enacting a new law, the Resource Recycling and Re-use Act (RRRA). However, it then became more complicated and recycling effectiveness was impeded. The causes were mainly the unclear definitions, conflicts about the scope, and issues between the RRRA and the Waste Disposal Act (WDA). This article examines the recycling legislation experience in Taiwan, and proposes two modifications for resolving these problems. The first proposal is merging these two acts into one. The second proposed modification maintains a two-system structure but introduces a new subject, discards, into the law. The subject of discards is further categorized as recyclable resources or waste, which correspond to recycling operations and disposal operations, respectively. The new structures, interfaces, prerequisites, properties, and comparisons are also explained.     

The degradation of gel-spun poly(β-hydroxybutyrate) “wool”

The apparent biodegradability and biocompatibility of the microbially produced polyester, poly(-hydroxybutyrate) (PHB), has been the focus of much research by a number of authors with regard to its potential for use in packaging and medical implantation devices. PHB has recently been produced by gel-spinning into a novel form, with one possible application being as a wound scaffolding device, designed to support and protect a wound against further damage while promoting healing by encouraging cellular growth on and within the device from the wound surface. This new nonwoven form combines a large volume with a low mass, has an appearance similar to that of cotton wool, and has been called wool because of this similarity. The hydrolytic degradation of this wool was investigated in an accelerated model of pH 10.6 and temperature 70°C. It was determined that the PHB wool gradually collapsed during degradation. The surface area-to-volume ratio was concluded to be a primary influencing factor. Degradation was characterized by a reduction in the glass transition temperatures and melting points and a fusion enthalpy peak of maximum crystallinity, (88%), which coincided with the point of matrix collapse.     

Preparation conditions and swelling equilibria of biodegradable hydrogels prepared from microbial poly(γ-glutamic acid) and poly(ε-lysine)

Biodegradable hydrogels prepared by -irradiation from microbial poly(amino acid)s are reviewed. pH-sensitive hydrogels were prepared by means of -irradiation of poly(-glutamic acid) (PGA) produced byBacillus subtilis IFO3335 and poly(-lysine) (PL) produced byStreptomyces albulus in aqueous solutions. The preparation conditions, swelling equilibria, hydrolytic degradation, and enzymatic degradation of these hydrogels were studied. A hydrogel with a wide variety of swelling behaviors has been produced by -irradiation from a mixture solution of PGA and PL.Paper presented at the 4th International Workshop on Biodegradable Plastics and Polymers, October 11–14, 1995, Durham, New Hampshire, USA.     

Synthesis of a block copolymer of poly(3-hydroxybutyrate) and poly(ethylene glycol) and its application to biodegradable polymer blends

A block copolymer {P[(R,S)-HB-b-EG]} of atactic poly[(R,S)-3-hydroxybutyrate] {P[(R,S)-HB]} and poly(ethylene glycol) (PEG) was prepared by the ring-opening polymerization of -butyrolactone in the presence of a macroinitiator (PEG/ZnEt₂/H₂O) which had been produced by the reaction of ,-dihydroxy PEG ( _n=3000) with ZnEt₂/H₂O (1/0.6) catalyst. The block copolymer ( _n=10,500, _w/ _n=1.2) was an A-B-A triblock copolymer comprising atactic P[(R,S)-HB] (A) and PEG (B) segments. The miscibility, physical properties, and biodegradability of binary blends of microbial poly[(R)-3-hydroxybutyrate] {P[(R)-HB]} with the block copolymer P[(R,S)-HB-b-EG] has been studied. The glass-transition temperature (T _g) data showed that the P[(R)-HB]/P[(R,S)-HB-b-EG] blend was miscible in the amorphous state. The P[(R)-HB] film became flexible and tough by means of blending with P[(R,S)-HB-b-EG] block copolymer. The enzymatic degradation of blend films was carried out at 37°C and pH 7.4 in a 0.1M phosphate solution of an extracellular PHB depolymerase fromAlcaligenes faecalis. The enzymatic degradation took place solely on the surface of the blend films.     

Application of the rescue number to the evaluation of remediation technologies for contaminated ground

An improved rescue number, RN_SOIL, which is an indicator for evaluating remediation technologies for contaminated ground that is based on both the risk and the remediation cost, is proposed as a tool of risk communication. The risk posed by contaminated ground is indicated by the figure of treatment priority at time t, FTP(t), which represents the human health risk as the number of people affected by the contaminated ground at time t during the remediation process. The calculation of the value of FTP(t) is based on exposure to contaminants that have migrated through environmental media from the contaminated ground, and is estimated by using a CalTOX model and the Monte Carlo method. The integration of FTP(t) with time, which represents the cumulative number of people affected by the contaminated ground, is used to estimate the performance of individual remediation technologies in risk reduction. The figure of unprocessibility for waste (FUW), which represents difficulties in remediation, is expressed as the remediation cost. FUW is estimated by using actual costs per unit volume of remediated soil. As an overall performance value, the rescue number for each remediation technology for contaminated ground (RN_SOIL) is calculated by multiplication of the integral FTP(t) by FUW. Smaller values of RN_SOIL are judged to indicate a better technology. The rescue index (RI), calculated as the ratio of the reduction of the integral FTP(t) to FUW, indicates the cost-effectiveness of the remediation technologies. Successful estimation of the indices (FTP(t), integral FTP(t), FUW, RN_SOIL and RI) demonstrate the usefulness of these indices in risk communication.Part of this paper was presented at 13th meeting of Japan Society of Waste Management Experts (2002)     

Radiation Effects on Blends of Poly(ε-Caprolactone) and Diatomites

Poly(-caprolactone) (PCL) was blended with diatomaceous earth (diatomite) and irradiated with -rays to introduce cross-linking between PCL molecules or both components. The unwashed diatomite containing a little of a volatile component showed high efficiency of introduction of cross-linking, whereas that with no volatile component showed low efficiency of introduction of cross-linking. Elongational viscosity, melt viscosity, and modulus of PCL/diatomite blend irradiated at various doses were significantly improved. Enzymatic degradation of the PCL/diatomite blend became faster than that of the PCL, though that of the blend irradiated became slower.     

Study of Trace and Heavy Metals in Rural and Urban Aerosols of Uludağ and Bursa (Turkey)

The concentrations of heavy, trace elements and major ions measuredin the Uluda and Bursa aerosols were investigated to assess size distributions, spatial and temporal variability, sources and source regions affecting the composition of aerosols in Uluda and Bursa. A total of 81 samples were collected in two sites, one in Bursa city and another in the Uluda Mountain during two sampling campaigns. Daily samples were collected using a high volume sampler on Whatman 41 cellulose filters in Uluda, while three days interval samples were collected in Bursa using an automatic dichotomous sampler on PTFE Teflon filters. Samples were analysed for 15 trace and heavy metals (Al, Fe, Ba, Na, Mg, K, Mn, Ca, Cu), (V, Pb, Cd, Cr, Ni, Zn), and 4 major ions (SO₄ ^2-, NO₃ ^-, Cl^-), (NH₄ ⁺) using ICP-AES, GFAAS, HPLC and UV/VIS Spectrophotometer,respectively. In general, concentrations of the metals measured inUluda aerosols were lower than those in Bursa. The concentrations of crustal elements were higher in summer than winter, while anthropogenic elements had higher concentrations in winter than summer. Most of the mass of crustal elements was concentrated in the coarse mode while the mass of the heavy metals was concentrated in the fine mode. Factor analysis revealed four factors with sources including crustal, industrial and combustion. Back trajectory calculations were used to determine long range contributions. These calculations showed that contributions were mostly from European countries, former Soviet Union countries, Black Sea and North Africa.     

Correlating the Spatial Distribution of Atmospheric Ammonia with δ15N Values at an Ammonia Release Site

A field ammonia (NH₃) release experiment and open top chambers containing moorland monoliths continuously fumigated with NH₃ or sprayed with NH₄Cl were used to assess the potential for using ¹⁵N values in determining the area of influence around a point NH₃ emission source. ¹⁵N values are being increasingly used as environmental tracers and we tested the hypothesis that the ¹⁵N signal from an NH₃ emission source is observable in nearby vegetation. Using modified monitoring devices, atmospheric NH₃ concentrations were found to decrease with distance from source, with ¹⁵N values also reflecting this trend, producing a signal shift with changing concentration. Open top chamber studies of ¹⁵N values of Calluna vulgaris (L.) Hull indicated a correlation with deposition treatments in current year shoots. Analysis of Calluna shoots from the NH₃ release showed a similar trend of ¹⁵N enrichment. Significant linear correlations between ¹⁵N and percent N in plant material were found, both in the controlled conditions of the open top chambers and at the NH₃ release site, illustrating the possible use of this technique in N deposition biomonitoring.     

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.