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PubMed2004

Development of nitrogen-removal bioreactor using poly(lactic acid) as an energy source.

To control nitrogen such as ammonia in a rearing water of aquatic animals, we developed new bioreactor capable of both nitrification and denitrification. It was consisted of gel-plate immobilized microorganisms and a biodegradable plastic plate composed of three kind of poly(lactic acid) as an energy source of denitrification. When batch treatment experiment by the bioreactor was continuously carried out with an artificial rearing water containing ammonia, nitrogen-removal rate of the bioreactor was approximately 3 g-N/d/m2-gel surface and the activity was maintained for over 3 month without additional energy source. Therefore, the bioreactor would be effective to control nitrogen concentration in rearing water of a closed water circulating system for aquatic animals.

Ammonia↗
PubMed2001

Thermophilic lactic acid production on hemicellulose hydrolysate.

Lactic acid has many applications. It can be utilised as road-deicing agent, in the food industry or--after polymerisation--as a biodegradable plastic. The use of lignocellulose biomass will significantly increase the competitiveness of lactic acid-based polymers compared to conventional petroleum based plastics. The Institute for Agrobiotechnology in Tulln (IFA-Tulln) developed a process to apply renewable resources as cheap feedstock for production of lactic acid. The utilisation of thermophiles combined with a suitable pretreatment method enables a fermentation under non sterile conditions with detoxified hemicellulosic hydrolysates. This paper presents growth toxicity tests and batch experiments with bagasse hydrolysate, which were conducted to determine the fermentability of thermophilic wild type strains.

Animal Feed↗
PubMed2006

Optimization of L-(+)-lactic acid production using pelletized filamentous Rhizopus oryzae NRRL 395.

Lactic acid is used as a food additive for flavor and preservation and a precursor in the development of poly-lactic acid, a product used to make biodegradable plastics and textiles. Rhizopus oryzae NRRL 395 is known to be a strain that produces optically pure L-(+)-lactic acid. The morphology of Rhizopus cultures is complex, forming filamentous, clumps, and pellet mycelia. Different morphology growth has significant effects on lactic acid production. In bioreactors, the filamentous or clump mycelia increase the viscosity of the medium, wrap around impellers, and block the nutrient transportation, leading to a decrease in production efficiency and bioreactor performance. Growing fungi in pellet form can significantly improve these problems. In this study, factors that affect lactic acid production in pelletized flask cultures using R. oryzae NRRL 395 were investigated in detail. Completely randomized designs were used to determine the influence of culture temperature, time, concentration of glucose, and inoculum size. Lactic acid fermentation using clump and pellet morphologies were performed in a 5 L fermentor at the optimal values obtained from flask culture. Finally, fed-batch culture was used to enhance the lactate concentration in broth. The final lactate concentration of fed-batch culture reached 92 g/L. The data presented in the article can provide useful information on optimizing lactic acid production using alternative source materials.

Biofilms↗
PubMed1990

[Coronary endoprostheses (stents)].

Even before the introduction of transluminal balloon dilatation of coronary arteries, Dotter had conceived intravascular endoprostheses and, in 1969, published a report of his observations after implantation of a spiral-shaped support of surgical steel and nickel-titanium ligation in peripheral arteries of the dog. Interest in intravascular supports developed especially in consideration of frequent unsatisfactory long-term results after coronary angioplasty. Coronary artery occlusion is observed in about 5% of balloon dilatations due to dissection, thrombosis, spasm or a combination of these phenomena. The rate of recurrent stenosis after uncomplicated balloon dilatation is about 30%, that of recanalization of chronic occlusion or dilatation of stenosed bypass grafts about 50%. Stent technology: In order to provide a meaningful solution to unresolved problems of balloon dilatation, the ideal endoprosthesis must be rapidly and reliably implantable as well as sufficiently flexible to conform to vascular curvatures. It should have a low profile, must be biocompatible and not thrombogenic; it should be rapidly endothelialized with no excessive proliferatory stimulus. Rigid stents are limited in length; elastic stents display a better transition to normal coronary arteries. Negatively-charged metallic surfaces appear less thrombogenic than those positively charged, the former, however, are usually not free of corrosion. The generally positive charge of stainless steel, the most commonly used material, is tempered with a special surface treatment. Currently, materials under investigation are nickel-titanium, tantalum and biodegradable plastic. Of importance for endothelialization are the wall thickness of the stent and the relationship of material to pore size. Filaments of stainless steel measuring 0.09 mm in diameter are completely covered by neoendothelium within three weeks. In laboratory animals, within minutes after implantation, all three stents currently in clinical use are covered with a thin layer of thrombocytes and fibrin; after one day, endothelial-like and pseudoendothelial cells develop along the metal structures. After one week, there is a flow-oriented behaviour of the surface cell formation embedding the stent between neoendothelial and lamina elastica interna, a process which is complete in three months. The thickness of the neointimal proliferation may be dependent on the stent geometry and may vary between 0.09 and 0.4 mm.(ABSTRACT TRUNCATED AT 400 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1982

Oral administration of peptides.

Newer methodologies allow us to reexamine the question of the oral administration of peptides. The design of proteolysis-resistant analogues, the synthesis of non-peptide active conformers, and the development of biodegradable plastic pill coatings are approaches that are theoretically possible. Which approach will be best for a given peptide will depend upon the properties of the active hormone and its receptor.

Administration, Oral↗
PubMed1992

[Food hygienic indexes on biodegradable polymers].

Current specifications for food packaging made of polyolefine plastics were applied to biodegradable plastics. No lead and cadmium were detected in any biodegradable plastic samples with the exception of bacterial cellulose, which contained trace amounts of lead and cadmium. Potassium permanganate consumption amount was less than the current specification level for polyofines. Sugars leached from bacterial cellulose was 22 +/- 1 microgram per 100 cm2 as glucose, and amino acids leached from poly-gamma-methylglutamate films was 8 +/- 3 micrograms per 100 cm2 as glutamic acid.

Amino Acids↗
PubMed2005

Encapsulation and sustained release of a model drug, indomethacin, using CO(2)-based microencapsulation.

A carbon dioxide (CO(2))-based microencapsulation technique was used to impregnate indomethacin, a model drug, into biodegradable polymer nanoparticles. Compressed CO(2) was emulsified into aqueous suspensions of biodegradable particles. The CO(2) plasticizes the biodegradable polymers, increasing the drug diffusion rate in the particles so that drug loading is enhanced. Four types of biodegradable polymers were investigated, including poly(d,l-lactic acid) (PLA), poly(d,l-lactic acid-co-glycolic acid) (PLGA) with two different molar ratios of LA to GA, and a poly(d,l-lactic acid-b-ethylene glycol) (PLA-PEG) block copolymer. Biodegradable nanoparticles were prepared from polymer solutions through nonsolvent-induced precipitation in the presence of surfactants. Indomethacin was incorporated into biodegradable nanoparticles with no change of the particle size and morphology. The effects of a variety of experimental variables on the drug loadings were investigated. It was found that the drug loading was the highest for PLA homopolymer and decreased in PLGA copolymers as the fraction of glycolic acid increased. Indomethacin was predicted to have higher solubility in PLA than in PLGA based on the calculated solubility parameters. The drug loading in PLA increased markedly as the temperature for impregnation was increased from 35 to 45 degrees C. Drug release from the particles is a diffusion-controlled process, and sustained release can be maintained over 10 h. A simple Fickian diffusion model was used to estimate the diffusion coefficients of indomethacin in the biodegradable polymers. The diffusion coefficients are consistent with previous studies, suggesting that the polymer properties are unchanged by supercritical fluid processing. Supercritical CO(2) is nontoxic, easily separated from the polymers, can extract residual organic solvent, and can sterilize biodegradable polymers. The CO(2)-based microencapsulation technique is promising for the production of drug delivery devices without the use of harmful solvents.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Insight in to the phylogeny of polyhydroxyalkanoate biosynthesis: horizontal gene transfer.

Polyhydroxyalkanoates (PHAs) are gaining more and more importance the world over due to their structural diversity and close analogy to plastics. Their biodegradability makes them extremely desirable substitutes for synthetic plastics. PHAs are produced in organisms under certain stress conditions. Here, we investigated 253 sequenced (completely and unfinished) genomes for the diversity and phylogenetics of the PHA biosynthesis. Discrepancies in the phylogenetic trees for phaA, phaB and phaC genes of the PHA biosynthesis have led to the suggestion that horizontal gene transfer (HGT) may be a major contributor for its evolution. Twenty four organisms belonging to diverse taxa were found to be involved in HGT. Among these, Bacillus cereus ATCC 14579 and Xanthomonas axonopodis pv. citri str. 306 seem to have acquired all the three genes through HGT events and have not been characterized so far as PHA producers. This study also revealed certain potential organisms such as Streptomyces coelicolor A3(2), Staphylococcus epidermidis ATCC 12228, Brucella suis 1330, Burkholderia sp., DSMZ 9242 and Leptospira interrogans serovar lai str. 56601, which can be transformed into novel PHA producers through recombinant DNA technology.

Biopolymers↗
PubMed2005

Metabolites from the biodegradation of di-ester plasticizers by Rhodococcus rhodochrous.

The plasticizers di-2-ethylhexyl phthalate (DEHP) and di-2-ethylhexyl adipate (DEHA) are ubiquitous in the environment and undergo partial biodegradation in the presence of soil micro-organisms. The validity of a proposed pathway for the degradation of these plasticizers by Rhodococcus rhodochrous has been confirmed by the identification of 2-ethylhexanal in gas phase emissions. Complete analyses of the aqueous and gas phases were able to account for more than 98% of the 2-ethylhexanol component of the DEHA added at the beginning of a growth study. Of this, 25% was either 2-ethylhexanol or 2-ethylhexanal that had been stripped into the gas phase and, at most, only 2% of the 2-ethylhexanol component could have been removed by mineralization. It is concluded that plasticizers are of significant environmental concern due to the resistance of the metabolites to biodegradation and their known health impacts. Two of the metabolites are of added concern due to their volatility and their potential impact on indoor air quality.

Adipates↗
PubMed2006

Staining and quantification of poly-3-hydroxybutyrate in Saccharomyces cerevisiae and Cupriavidus necator cell populations using automated flow cytometry.

BACKGROUND: Poly [(R)-3-hydroxybutyric acid] (PHB) is a prokaryote storage material for carbon and energy that accumulates in cells under unbalanced growth conditions. Because this class of biopolymers has plastic-like properties, it has attracted considerable interest for biomedical applications and as a biodegradable commodity plastic. Current flow cytometric techniques to quantify intracellular PHB are based on Nile red. Here, an improved cytometric technique for cellular PHB quantification utilizing BODIPY 493/503 staining was developed. This technique was then automated using an automated flow cytometry system. MATERIALS: Using flow cytometry, the fluorescence of Saccharomyces cerevisiae and Cupriavidus necator with varying PHB content after staining with BODIPY 493/503 and Nile red was compared, and automated staining techniques were developed for both cultures. RESULTS: BODIPY 493/503 staining had less background staining, higher sensitivity and specificity to PHB, and higher saturation values than did Nile red staining. The developed automated staining procedure was capable of analyzing the PHB content of a bioreactor sample every 25 min and measured the average PHB content with accuracy comparable to offline GC analysis. CONCLUSION: BODIPY 493/503 produced an overall better staining for PHB than did Nile red. When combined with the automated system, this technique provides a new method for the online monitoring and control of bioreactors.

Boron Compounds↗
PubMed2006

Interaction of metabolites with R. rhodochrous during the biodegradation of di-ester plasticizers.

The commonly used plasticizers di-ethylhexyl phthalate (DEHP) and di-ethylhexyl adipate (DEHA) are known to partially degrade in the presence of soil microorganisms, such as Rhodococcus rhodochrous, releasing persistent and toxic metabolites. The metabolites adipic acid and 2-ethylhexanol were both shown to inhibit growth of the degrading microbe. 2-Ethylhexanol enhanced the activity of ethanol dehydrogenase - an enzyme involved in its metabolism - but the activity of this enzyme was inhibited by adipic acid. The metabolite usually seen in the highest concentrations - 2-ethylhexanoic acid - did not exhibit any evidence of inhibition. It was shown that the high concentration of this metabolite was due to the inability of R. rhodochrous to degrade it. Comparisons with other small carboxylic acids supported the argument that the ethyl branch was the reason for the resistance of 2-ethylhexanoic acid to degradation. The hydrophobicity of the cell surface was shown to be a factor in plasticizer degradation. The primary carbon source could be either water-soluble or hydrophobic and a hydrophobic substrate led to a cell surface that attracted the plasticizer and facilitated degradation. The most hydrophobic of the plasticizers, DEHP, was particularly sensitive to this effect.

Adipates↗
PubMed2003

Starch-based plastic polymer degradation by the white rot fungus Phanerochaete chrysosporium grown on sugarcane bagasse pith: enzyme production.

In this study, starch metabolites and enzymes were determined during starch-based plastic polymer biodegradation by the white rot fungus Phanerochaete chrysosporium, grown in sugarcane bagasse pith in tubular reactors. Various metabolites, amylase, ligninase and cellulase production were measured during P. chrysosporium growth on sugarcane bagasse pith with added glucose and starch polymer. On-line respirometric analyses followed during 32 days confirmed the P. chrysosporium capability of growing on sugarcane bagasse pith with starch polymer degradation. Enzyme activity during secondary metabolism increased, and a 70% and 74% starch degradation was reached with and without glucose addition, generating low molecular weight metabolites (e.g.) dextrin, maltotriose, maltose and glucose that were detected by high performance liquid chromatography.

Amylases↗
PubMed1990

Plastics from bacteria and for bacteria: poly(beta-hydroxyalkanoates) as natural, biocompatible, and biodegradable polyesters.

Hence, PHB belongs to the family of poly(beta-hydroxyalkanoates), PHA, all of which are usually formed as intracellular inclusions under unbalanced growth conditions. Recently, it became of industrial interest to evaluate PHA polyesters as natural, biodegradable, and biocompatible plastics for a wide range of possible applications such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such "tailormade" copolymers can be produced under controlled growth conditions, in that if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

Bacteria↗
PubMed2004

Effect of plasticization on heparin release from biodegradable matrices.

Heparin-loaded polymer films of poly-L-lactide (PLLA) and poly-L-lactide-co-glycolide (PLLGA) as well as poly-DL-lactide-co-glycolide (PLGA) were produced. A plasticizer, PEG, was added to the polymers. It was found that the release profile in general consisted of a burst effect, a diffusion-controlled phase and a degradation-controlled phase. The plasticizer accelerated the onset of degradation in all cases, but its effect on the release profile differed significantly depending on the polymer. The plasticizer depressed the burst effect for PLLA, and accelerated the kinetics of the diffusion-controlled phase. For the PLLGA 80/20, however, the plasticizer had no significant effect on the release profile or kinetics. We explain these observations in terms of hydrophilicity and crystallinity effects.

Absorbable Implants↗
PubMedDate not supplied

Plastics in refuse.

Explore the source record for details and available documents.

Biodegradation, Environmental↗
PubMed2004

[Effect of triester glycerol type of plasticizers on release of albumin from biodegradable polymer matrices].

Bovine serum albumin was heterogeneously dispersed in the terpolymer of DL-lactic acid, glycolic acid, and mannitol. The terpolymeric carrier was plasticized by triacetin, tributyrin, or a mixture of triacetin with tricaprylin. Matrices were prepared by mixing a melt of the carrier with the plasticizer and albumin. Liberation was tested in 1/15 mol.l-1 phosphate buffer pH 7.4 and took place in two stages--the burst and the stage of the continual process. The burst represented 30% to 90% of liberated albumin. The second, continual stage began on day 4 of liberation and within ten days maximally 10% of the total amount of albumin was released. The course of liberation was most markedly influenced by the parameters of the oligoester carrier, its molecular weight, and the degree of branching. The total extent of albumin liberation was influenced partly by its irreversible adsorption on the carrier, partly by its polymerization. The extent of adsorption and polymerization of albumin was increased with the molecular weight of the carrier and decreased with the increasing degree of its branching. Albumin liberation was positively influenced by the presence of plasticizers in matrices, triacetin being demonstrated as the best one.

Biodegradation, Environmental↗