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PubMed1996

Absorbable devices in the fixation of fractures.

Totally absorbable internal fracture fixation devices were introduced clinically in the treatment of fractures and osteotomies of the extremities at our department in 1984. A total of 2,500 patients were managed using bone or ligament fixation devices made of self-reinforced (matrix and fibers of same polymer) absorbable alpha-hydroxy polyesters between November 5, 1984, and January 12, 1994. The devices used included cylindrical rods or pins, screws, tacks, plugs, and wires. The most common indication for the use of absorbable implants was displaced malleolar fracture of the ankle. Transphyseal fixation with small-diameter polyglycolide pins was used in children. The postoperative clinical course was uneventful in over 90% of the patients. The complications included bacterial wound infection in 3.6% and failure of fixation in 3.7%. In one-fifth of these cases, however, reoperation was not necessary. The occurrence of noninfectious foreign-body reactions 2 to 3 months postoperatively has been observed in 2.3% of the patients operated in the last years with polyglcolide implants but in none of the patients with polylactide implants. This inflammatory tissue response often required aspiration with a needle or small incision but did not influence the ultimate functional or radiologic result of treatment. Owing to the biodegradability of these internal fixation devices, over 1,000 implant removal procedures were avoided during the 9-year period under review, allowing medical personnel at these facilities to focus on other procedures. Avoidance of removal procedures results in financial benefits and psychological advantages. The benefits of absorbable implants for war surgery are the same as for civilian life. Absorbable implants can also be used in open fractures and infection operations.

Absorption↗

PubMed1996

Periareolar mammaplasty: double skin technique with application of polyglactine or mixed mesh.

This paper presents the author's experience of 7 years in 254 patients operated on using a personal mammaplasty technique with a periareolar approach. The technique is based on the principle that the skin alone does not prevent early ptosis. This paper proposes the repositioning of all breast connective structures, treating the glandular set separately from the cutaneous lining, which is doubled, applying a circular flap of dermis with the central pedicle to the areolar region. For this purpose, the following structures have been employed, which, once repositioned and together, will act as a support network: (1) anterior pectoral fascia, (2) Cooper's intramammary ligament, (3) periareolar dermal flap, employed as skin inner lining. (4) application of absorbable polyglactine 910 or mixed mesh (with polyester) as a sandwich between both layers of skin, and (5) external cutaneous lining that composes the assembly of double skin.

Adult↗

PubMed1994

Multidirectional stability of the Graf system.

STUDY DESIGN: To assess the biomechanical influences of the Graf fixation system on the spine, motion segments were tested. In normal spines, destabilized and restabilized with the Graf system conditions, the range of motion and flexibilities were found under various loading conditions. OBJECTIVES: These results should explain how the Graf Fixation system affects the biomechanical response of a motion segment. METHODS: Motion segments (L2-3) and (L4-5) were subjected to these loading conditions: compressive loading, flexion-extension, lateral bending, and axial rotation moments. During the loading, the main and coupled motions were measured, and flexibilities were computed. The position of the balance point in axial loading was also determined. The motion segments were tested under three conditions: intact, destabilized, and restabilized. The destabilization consisted of a bilateral total laminectomy (pedicle-to-pedicle). Restabilization was affected with the Graf stabilization system, consisting of polyester bands between pedicle screw implants. RESULTS: The total laminectomy significantly changed the balance point location by moving it forward. The restabilized motion segment had a balance point more similar to normal conditions. The mean compressive compliance was significantly less after application of the Graf system compared with destabilization. The range of motion for flexion-extension and axial rotation was significantly reduced for the main motion with the Graf system. For lateral bending, the main and coupled rotations were affected significantly, with lateral bending and flexion-extension motion reduced and axial rotation increased after restabilization. Restabilization decreased the flexibility of the destabilized motion segment for all of the moments. CONCLUSIONS: The Graf fixation system reduced the range of motion and the flexibility values in some loading conditions. These results only assess the immediate stabilization characteristics of this implant system in cadaveric material. Further research should address the fatigue characteristics.

Biomechanical Phenomena↗

PubMedDate not supplied

Indium-111-oxine-labeled platelet scintigraphic images in the assessment of thrombogenicity in small-caliber prosthetic vascular grafts.

Anti-thrombogenicity is one of the essential factors for successful development of small-caliber prosthetic vascular grafts, and its accurate evaluation is important. The purpose of this study was to investigate the efficacy of indium-111-oxine-labeled (In) platelet scintigraphic images in the assessment of graft thrombogenicity. Fibrin-coated knitted polyester vascular prostheses, 2 mm in diameter and 2 cm in length, were implanted in the bilateral common carotid arteries of 18 Japanese white rabbits. The grafts were explanted on postoperative days 1, 3, 7, 10, 14, and 30 (six grafts on each of the days), and In platelet scintigraphy was performed with visual, semiquantitative, and quantitative analysis. The relationships among the three analyses were evaluated. Platelet depositions on the luminal surface were clearly visualized with In-platelet scintigraphy if the number of In platelets was more than 4.8 x 10 counts per minute, even if a macroscopic thrombus formation was not observed. There was a highly significant correlation between the graft region of interest on the images and the total platelet deposition (p<.0001). The images in the thrombotic grafts have shown a very strong In-platelet accumulation, but there were some limitations in the In-platelet scintigraphic images. In-platelet scintigraphic images are useful for evaluating platelet deposition in small-caliber vascular prostheses if they are performed with a proper understanding of their limitations.

Animals↗

PubMedDate not supplied

Increase in cell adhesiveness on a poly(ethylene terephthalate) fabric by sintered hydroxyapatite nanocrystal coating in the development of an artificial blood vessel.

Nano-scaled sintered hydroxyapatite (HAp) crystals were covalently linked onto a poly(ethylene terephthalate) (PET) fabric substrate chemically modified by graft polymerization with gamma-methacryloxypropyl triethoxysilane (MPTS) for development of an artificial blood vessel. The weight gain of graft polymerization with poly(MPTS) on PET in benzyl alcohol containing H2O2 as an initiator increased as increasing the reaction time and finally reached a plateau value of about 3.5 wt%. The surface characterization of surface modification with poly(MPTS)-grafting was conducted by x-ray photoelectron spectroscopy. HAp nanocrystals of approximately 50 nm in diameter, monodispersed in pure ethanol, were coupled with alkoxysilyl groups of the poly(MPTS)-grafted PET substrate. The HAp nanocrystals were uniformly and strongly coated on the surface of the PET fabrics, although HAp particles adsorbed physically on the original PET without poly(MPTS) grafting were almost removed by ultrasonic wave treatment. More human umbilical vein endothelial cells adhered to the HAp/PET composite fabric compared with original PET after only 4 hours of initial incubation, and the same was observed on the collagen-coated PET. The coating of sintered HAp nanocrystals imparted bioactivity to the polyester substrate, which is a widely used biomedical polymer, without a coating of adhesion proteins derived from animals, such as collagen or gelatin. A prototype of an artificial blood vessel was finally fabricated by use of HAp/PET composite.

Adhesiveness↗

PubMed2001

Identification of a new class of biopolymer: bacterial synthesis of a sulfur-containing polymer with thioester linkages.

This is the first report on the biosynthesis of a hitherto unknown, sulfur-containing polyester and also the first report on a bacterial polymer containing sulfur in the backbone. The Gram-negative polyhydroxyalkanoate (PHA)-accumulating bacterium Ralstonia eutropha synthesized a copolymer of 3-hydroxybutyrate and 3-mercaptopropionate, poly(3HB-co-3MP), when 3-mercaptopropionic acid or 3,3'-thiodipropionic acid was provided as carbon source in addition to fructose or gluconic acid under nitrogen-limited growth conditions. The peculiarity of this polymer was the occurrence of thioester linkages derived from the thiol groups of 3MP and the carboxyl groups of 3MP or 3HB, respectively, which occurred in addition to the common oxoester bonds of PHAs. Depending on the cultivation conditions and the feeding regime, poly(3HB-co-3MP) contributed up to 19% of the cellular dry weight, with a molar fraction of 3MP of up to 43%. The chemical structure of poly(3HB-co-3MP) was confirmed by GC/MS, IR spectroscopy, (1)H- and (13)C-NMR spectroscopy, and elemental sulfur analysis. The identification of this novel biopolymer reveals a new quality regarding the substrate range of PHA synthases and their capability for the synthesis of technically interesting polymers.

3-Hydroxybutyric Acid↗

PubMed2001

Multiple evidence for widespread and general occurrence of type-III PHA synthases in cyanobacteria and molecular characterization of the PHA synthases from two thermophilic cyanobacteria: Chlorogloeopsis fritschii PCC 6912 and Synechococcus sp. strain MA19.

Eleven different cyanobacteria were investigated with respect to their capabilities to synthesize poly-3-hydroxybutyrate [poly(3HB)] and the type of poly-beta-hydroxyalkanoic acid (PHA) synthase accounting for the synthesis of this polyester. Several methods, including (i) Southern blot analysis using a phaC-specific DNA probe, (ii) Western blot analysis using specific polyclonal anti-PhaE antibodies raised in this study against PhaE of Synechocystis sp. strain PCC 6803, (iii) generation and sequence analysis of PCR products using phaC-specific oligonucleotides as primers, and/or (iv) cloning and sequence analysis of PHA synthase structural genes, were used to provide evidence for the presence of a type-III PHA synthase in the following cyanobacteria: Synechococcus sp. strains MA19 and PCC 6715, Chlorogloeopsis fritschii PCC 6912, Anabaena cylindrica SAG 1403-2, Cyanothece sp. strains PCC 7424, PCC 8303 and PCC 8801, and Gloeocapsa sp. strain PCC 7428. The screening was compared with corresponding studies using crude protein extracts and genomic DNA of Synechocystis sp. strain PCC 6803, as a positive control, which is so far the only cyanobacterium for which molecular data of the PHA synthase genes are available. No evidence for the presence of a type-III PHA synthase could be obtained for only three of the eleven investigated cyanobacteria (Stanieria sp. strain PCC 7437, Cyanothece sp. strain PCC 8955 and Gloeothece sp. strain PCC 6501). The entire PHA synthase structural genes of the two thermophilic cyanobacteria Synechococcus sp. strain MA19 and Chlorogloeopsis fritschii PCC 6912, and in addition a central region of the phaC gene of Cyanothece sp. strain PCC 8303, were cloned, sequenced and also heterologously expressed in Escherichia coli.

Acyltransferases↗

PubMed2001

Polyhydroxybutyrate biosynthesis in Caulobacter crescentus: molecular characterization of the polyhydroxybutyrate synthase.

Caulobacter crescentus was investigated with respect to polyhydroxybutyrate (PHB) biosynthesis. Polyhydroxyalkanoate (PHA) accumulation contributing to approximately 18% of the cell dry weight was obtained in the presence of glucose. Gas chromatography-mass spectrometry and gel permeation chromatography of the purified PHA showed that this polyester was solely composed of 3-hydroxybutyrate and had a weight average molar mass of 5.5 x 10(5) g mol(-1) and a polydispersity of 1.6. An ORF encoding a conserved, hypothetical protein which shared approximately 47% identity with the PHB synthase from Azorhizobium caulinodans was identified within the complete C. crescentus genomic sequence. This putative C. crescentus PHB synthase gene, phaC, consisted of a 2019 nt stretch of DNA (encoding 673 aa residues), which encoded a PHB synthase with a molecular mass of approximately 73 kDa. This is currently the largest PHA synthase identified. The phaC coding region was subcloned into vector pBBR1-JO2 under lac promoter control. The resulting plasmid, pQQ4, mediated PHB accumulation in the mutant Ralstonia eutropha PHB(-)4 and recombinant Escherichia coli JM109(pBHR69), which produced the beta-ketothiolase and acetoacetyl-CoA reductase from R. eutropha, contributing to approximately 62% and 6% of cell dry weight, respectively. Functional expression of the coding region of phaC was confirmed by immunoblotting and in vitro PHB synthase activity.

Acyltransferases↗

PubMed2001

Alginate formation in Azotobacter vinelandii UWD during stationary phase and the turnover of poly-beta-hydroxybutyrate.

Azotobacter vinelandii UWD is a mutant of strain UW that is defective in the respiratory oxidation of NADH. This mutation causes an overproduction of polyhydroxyalkanoates (PHAs), as polyester synthesis is used as an alternative electron sink. Since PHAs have potential for use as natural, biodegradable plastics, studies of physiology related to their production are of interest. Alginate production by this strain is limited to < 11 microg (mg cell protein)(-1), which permits high efficiency conversion of carbon source into PHA. However, < or = 400 microg (mg cell protein)(-1) was formed when UWD cells were oxygen-limited and in the stationary phase of growth. Alginate formation was fuelled by PHA turnover, which was coincident with the synthesis of alkyl resorcinols, under conditions of exogenous glucose limitation. However, alginate production was a phenotypic and reversible change. Alginate production was stopped by interruption of algD with Tn5lacZ. LacZ activity in UWD was shown to increase in stationary phase, while LacZ activity in a similarly constructed mutant of strain UW did not. Transcription of algD in strain UWD started from a previously identified RpoD promoter and not from the AlgU (RpoE) promoter. This is because strain UWD has a natural insertion element in algU. Differences between strain UW and UWD may reside in the defective respiratory oxidation of NADH, where the NADH surplus in strain UWD may act as a signal of stationary phase. Indeed, a backcross of UW DNA into UWD generated NADH-oxidase-proficient cells that failed to form alginate in stationary phase. Evidence is also presented to show that the RpoD promoter may be recognized by the stationary phase sigma factor (RpoS), which may mediate alginate production in strain UWD.

Alginates↗

PubMed2003

Thermomonas fusca sp. nov. and Thermomonas brevis sp. nov., two mesophilic species isolated from a denitrification reactor with poly(epsilon-caprolactone) plastic granules as fixed bed, and emended description of the genus Thermomonas.

Previously, 22 aerobic Gram-negative bacteria were isolated from biofilms growing on granules of the synthetic polyester poly(epsilon-caprolactone); the granules were used as a fixed bed in a denitrification reactor. All the strains showed similar fatty acid profiles. The 16S rRNA gene sequences of five strains were phylogenetically related to Thermomonas spp. Repetitive extragenic palindromic DNA-PCR (REP-PCR) fingerprinting revealed four groups, and DNA hybridizations between representative strains showed that the strains belonged to two new species within the genus Thermomonas, for which the names Thermomonas fusca (type strain LMG 21737(T)=DSM 15424(T)) and Thermomonas brevis (type strain LMG 21746(T)=DSM 15422(T)) are proposed. Both species are able to grow at low temperatures, but not at 50 degrees C, and are non-haemolytic. Both species can be differentiated by several other phenotypic features from earlier described species of the genus Thermomonas. Cell extracts contain mainly branched fatty acids, with C(15 : 0) iso, C(17 : 1) iso omega9c, C(11 : 0) iso 3OH and C(11 : 0) iso as main constituents. The G+C content of the DNA of the novel species is between 67.6 and 68.7 mol%.

Biofilms↗

PubMed2005

In vitro testing of fungicidal activity of biocides against Aspergillus fumigatus.

The activity of biocides against Aspergillus fumigatus is unknown. In the European guidelines to evaluate the fungicidal activity of a biocide, the critical step concerning the preparation of conidial suspensions is cumbersome and time-consuming. The aims of this study were to evaluate a simplified procedure to prepare conidial suspensions to test a biocide in comparison with the recommended one and to investigate the in vitro activity of seven biocides by the suspension neutralization method against A. fumigatus clinical isolates. The proposed simplified procedure proved reproducible, gave the same results and was quicker than that described in the European guidelines. Benzalkonium chloride (0.25 %), glutaraldehyde (1.6 %), polyvinylpyrrolidone iodine (1 % available iodine) and polyester glycol iodine (0.18 % available iodine) showed biocidal activity in <or=5 min contact time, and chlorine (0.14 % available Cl) and chlorhexidine (0.06 %) after 15 min and 30-60 min, respectively. In contrast, chloramine-T (0.01 %) did not show biocidal activity. In addition, a simplified and reproducible procedure may be used for testing the fungicidal activity of new compounds or combined formulations. In conclusion, the biocides tested, which are commonly used in hospital settings, were shown to display biocidal activity against A. fumigatus and a simplified procedure may be adopted for testing the fungicidal activity of new compounds.

Anti-Infective Agents, Local↗

PubMed2005

Cuticular lipid composition, surface structure, and gene expression in Arabidopsis stem epidermis.

All vascular plants are protected from the environment by a cuticle, a lipophilic layer synthesized by epidermal cells and composed of a cutin polymer matrix and waxes. The mechanism by which epidermal cells accumulate and assemble cuticle components in rapidly expanding organs is largely unknown. We have begun to address this question by analyzing the lipid compositional variance, the surface micromorphology, and the transcriptome of epidermal cells in elongating Arabidopsis (Arabidopsis thaliana) stems. The rate of cell elongation is maximal near the apical meristem and decreases steeply toward the middle of the stem, where it is 10 times slower. During and after this elongation, the cuticular wax load and composition remain remarkably constant (32 microg/cm2), indicating that the biosynthetic flux into waxes is closely matched to surface area expansion. By contrast, the load of polyester monomers per unit surface area decreases more than 2-fold from the upper (8 microg/cm2) to the lower (3 microg/cm2) portion of the stem, although the compositional variance is minor. To aid identification of proteins involved in the biosynthesis of waxes and cutin, we have isolated epidermal peels from Arabidopsis stems and determined transcript profiles in both rapidly expanding and nonexpanding cells. This transcriptome analysis was validated by the correct classification of known epidermis-specific genes. The 15% transcripts preferentially expressed in the epidermis were enriched in genes encoding proteins predicted to be membrane associated and involved in lipid metabolism. An analysis of the lipid-related subset is presented.

Arabidopsis↗

PubMed2004

Plasma quality after whole-blood filtration depends on storage temperature and filter type.

The study evaluated the quality of plasma obtained after whole-blood filtration with four different polyester filters and one polyurethane filter. The activities of coagulation factors and proteinase inhibitors were not or only negligibly affected by filtration, in all experiments. Filtration did not increase markers of clotting and fibrinolysis. Only a strong neutrophil and complement activation was observed, which depended on the type of filter and whole-blood storage conditions. However, as neutrophil elastase-specific degradation products did not increase and the complement-derived anaphylatoxin C3a was found in its inactivated form, C3a-desArg, these filtration-dependent changes apparently have little impact on the therapeutic quality of whole-blood-filtered fresh frozen plasma for transfusion.

Antithrombins↗

PubMed1996

Comparison of different insecticides and fabrics for anti-mosquito bednets and curtains.

Various formulations of six insecticides (a carbamate and five pyrethroids), were impregnated into bednets and curtains made from cotton, polyester, polyethylene or polypropylene fabric. For bioassays of insecticidal efficacy, female Anopheles gambiae mosquitoes were made to walk on the fabrics for 3 min and mortality was scored after 24 h. The main concentrations tested were: bendiocarb 400 mg/m2, cyfluthrin 30-50 mg/m2, deltamethrin 15-25 mg/m2, etofenprox 200 mg/m2, lambda-cyhalothrin 5-15 mg/m2 and permethrin 200-500 mg/m2. Field trials in Tanzania used experimental huts (fitted with verandah traps) entered by wild free-flying Anopheles gambiae, An.funestus and Culex quinquefasciatus mosquitoes. Results of testing the impregnated fabrics in experimental huts showed better personal protection provided by bednets than by curtains. Permethrin cis:trans isomer ratios 25:75 and 40:60 were equally effective, and the permethrin rate of 200 mg/m2 performed as well as 500 mg/m2. Bioassay data emphasized the prolonged insecticidal efficacy of lambda-cyhalothrin deposits, except on polyethylene netting. Most of the impregnated nets (including the 'Olyset' net with permethrin incorporated during manufacture of the polyethylene fibre) and an untreated intact net performed well in preventing both Anopheles and Culex mosquitoes from feeding on people using them overnight in the experimental huts. Anopheles showed high mortality rates in response to pyrethroid-treated nets, but only bendiocarb treated curtains killed many Culex. Holed nets treated with either cyfluthrin (5 EW formulation applied at the rate of 50 mg a.i./m2) or lambda-cyhalothrin (2.5 CS formulation at 10 mg a.i./m2) performed well after 15 months of domestic use. Treatment with deltamethrin SC or lambda-cyhalothrin CS at the very low rate of 3 mg/m2 gave good results, including after washing and re-treatment.

Animals↗

PubMed1989

Leukocyte-poor platelet concentrates at the bedside by filtration through Sepacell-PL.

We developed a new filter, 'Sepacell-PL', consisting of a blood administration set for the preparation of leukocyte-poor platelet concentrates at the patient's bedside. This filter is packed with 1.8 microns polyester fibers coated with a new polymer, and has a volume of 14 ml. Sepacell-PL removed more than 99% of the leukocytes while approximately 93% of platelets were recovered from 10 units of platelet concentrates which contained 5 x 10(8) leukocytes and 3 x 10(11) platelets. The functions of pre- and postfiltrated platelets were unchanged. The filtration procedure is very simple, without priming with saline to remove air and wet the filter. Moreover, platelet concentrates can be passed through the filter at a flow rate of 4 ml/min, or at a higher flow rate of 54 ml/min by gravity.

Blood Transfusion↗

PubMed2006

Poly (epsilon-caprolactone) grafted with nano-structured chitosan enhances growth of human dermal fibroblasts.

Polyester films are modified with their bioactivity for tissue engineering by grafting a nano-structured bioactive material, nano-structured chitosan (nano-CS), on a model polymer, poly (epsilon-caprolactone) (PCL). The nano-CS was duplicated using a solvent-etched PCL mold and then grafted onto PCL using a selected solvent. The structure of the nano-CS/PCL surface was characterized using an atomic force microscope to observe the topography and determine the roughness. The centerline average roughness, Ra, of the surface of the nano-CS/PCL film is 106.0+/-4.0 nm whereas that of the surface of the CS-grafted PCL film (CS/PCL) is 3.6+/-0.4 nm. The latter is therefore very smooth. CS is known to swell following hydration, so the Ra values were determined again after immersion for 12 h in phosphate buffered saline. Although the centerline average roughness of the nano-CS/PCL was lower, it still markedly exceeded that of the CS/PCL film. Cells grown on nano-CS/PCL, CS/PCL, nano-structured PCL (nano-PCL), and PCL films were observed by fluorescent staining and analyzed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) viability assay following 3 and 7 days of culture, to evaluate the effects of the design on the growth of fibroblasts. The viability assay of the cells reveals that the growth rate of cells on both CS/PCL and nano-CS/PCL films significantly exceeds (P<0.001) those of PCL and nano-PCL films on both cultural days. Additionally, the growth rate and proliferation of fibroblasts on nano-CS/PCL films significantly exceed (P<0.001) those on CS/PCL films after both periods of culturing, suggesting that the bioactive surface following a nano-structured treatment promotes the growth rate of cells. However, nano-PCL films do not have the same effects as nano-CS/PCL films do. In conclusion, a novel biomaterial, nano-CS/PCL, is developed by grafting a nano-structured bioactive surface, CS, onto the PCL surface to promote the the growth rate of fibroblasts. This work elucidates a new concept for designing films or scaffolds for tissue engineering-the grafting of nano-structured bioactive biomaterials to the films or scaffolds to promote the growth of cells.

Caproates↗

PubMed1992

Molecular basis for biosynthesis and accumulation of polyhydroxyalkanoic acids in bacteria.

The current knowledge on the structure and on the organization of polyhydroxyalkanoic acid (PHA)-biosynthetic genes from a wide range of different bacteria, which rely on different pathways for biosynthesis of this storage polyesters, is provided. Molecular data will be shown for genes of Alcaligenes eutrophus, purple non-sulfur bacteria, such as Rhodospirillum rubrum, purple sulfur bacteria, such as Chromatium vinosum, pseudomonads belonging to rRNA homology group I, such as Pseudomonas aeruginosa, Methylobacterium extorquens, and for the Gram-positive bacterium Rhodococcus ruber. Three different types of PHA synthases can be distinguished with respect to their substrate specificity and structure. Strategies for the cloning of PHA synthase structural genes will be outlined which are based on the knowledge of conserved regions of PHA synthase structural genes and of the PHA-biosynthetic routes in bacteria as well as on the heterologous expression of these genes and on the availability of mutants impaired in the accumulation of PHA. In addition, a terminology for the designation of PHAs and of proteins and genes relevant for the metabolism of PHA is suggested.

Acyltransferases↗

PubMed1999

Isolation of poly(beta-L-malic acid)-degrading bacteria and purification and characterization of the PMA hydrolase from Comamonas acidovorans strain 7789.

Several bacteria were isolated which were able to utilize poly(beta-L-malic acid) as sole carbon source for growth. The poly(beta-L-malic acid) hydrolyzing enzyme of Comamonas acidovorans strain 7789 was detected in the membrane fraction. The enzyme was purified by isolation of crude cell membranes by ultracentrifugation of disrupted cells, solubilization of the membrane fraction with octylglucoside, selective precipitation with 50% saturated ammonium sulfate and preparative isolectric focusing. SDS-PAGE analysis revealed a M(r) of 43,000. The pH optimum was 8.1 and the Km was 0.13 microM (in terms of monomeric units) and 0.0021 microM poly(beta-L-malic acid) at pH 8.1 (100 mM glycylglycine buffer). Addition of NaCl, KCl, CaCl2 or MgCl2 (from 25 to 100 mM) decreased the hydrolase activity, whereas EDTA or polymethane sulfonic acid fluoride had no influence on the enzyme. The depolymerization of poly(beta-L-malic acid) proceeded from the ends of the polyester resulting in the formation of L-malate. Esterase activity was not detectable with p-nitrophenyl acetate or p-nitrophenyl butyrate, which is used to determine for example poly(3-hydroxybutyric acid) depolymerase activity.

Biodegradation, Environmental↗