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PubMedDate not supplied

Removal of high phenol concentrations with adapted activated sludge in suspended form and entrapped in calcium alginate /cross-linked poly(N-vinyl pyrrolidone) hydrogels.

The present work evaluates the aerobic removal of 0.25-2 g/L of phenol by adapted activated sludge in batch and continuous reactors, in suspended form and trapped in polymeric hydrogel beads of calcium alginate(1%) and cross-linked poly(N-vinyl pyrrolidone), x-PVP (4%). The mechanical and chemical resistance of the entrapping hydrogel was also evaluated in three different media: (I) rich in phosphate and ammonium ions; (II) using alternate P and N sources, and (III) without nutrients. The adapted consortium removed phenol concentrations up to 2 g/L more efficiently in the immobilized systems. A decrease in phenol removal rate was observed as the food/microorganisms (F/M) ratio increased. A zero-order kinetics was observed with phenol concentrations > 1 g/L and a first-order kinetics at concentrations < 1 g/L. The best response (100% removal) was in the continuous reactors using type II medium, with a hydraulic residence time (HRT) of 12.5 h, an influent pH = 5, and an F/M ratio below 0.25. The immobilizing matrix deteriorated after 170 h of use in continuous reactors, especially with media I and II, probably due to the attrition forces, to chemical weakness of the material, and to the pressure of the bacterial growth inside the bead.

Alginates↗
PubMed2003

Cooperative biosorption of copper on calcium alginate enclosing iminodiacetic type resin.

Composite gels of calcium alginate containing iminodiacetic type resin were prepared as a chemical analogue of biological tissues and membrane such as the cell wall. This chemical model was applied in copper biosorption from synthetic aqueous solutions. Experimental data on the composite were compared to those obtained for the biopolymer and the iminodiacetic-type resin separately and fitted into the ion exchange equilibrium model proposed in this work, which basically assumes that metal retention is the sum of the metal loaded onto the biopolymer and onto the resin. This model is tested with experimental data on copper biosorption on composite gels, including the equilibrium expressions of all the ionic species that are present in the system, the fraction of metal enclosed in the gel fluid, the gel volume variation, and the Donnan equilibrium theory. Another simplified model that only requires one equilibrium constant for each metal in the resin is shown to fit the results of the experiment fairly well, but it proves necessary to include an empirical parameter n into the equilibrium equation of copper in the resin to obtain the best fit of experimental data.

Adsorption↗
PubMed2000

Determination of the absolute molecular weight averages and molecular weight distributions of alginates used as ice cream stabilizers by using multiangle laser light scattering measurements.

High-performance size exclusion chromatography with multiangle laser light scattering detection (HPSEC-MALLS) was used for characterizing complete molecular weight distributions for a range of commercial alginates used as ice cream stabilizers. For the samples investigated, molecular weight averages were found to vary between 115 000 and 321 700 g/mol and polydispersity indexes varied from 1. 53 to 3.25. These samples displayed a high content of low molecular weights. Thus, the weight percentage of material below 100 000 g/mol ranged between 6.9 and 54.4%.

Alginates↗
PubMed2003

Stability and emulsion-forming ability of water-soluble fish myofibrillar protein prepared by conjugation with alginate oligosaccharide.

Carp myofibrillar protein (Mf) was conjugated with alginate oligosaccharide (AO) through the Maillard reaction under low relative humidity, and the functional properties of the Mf-AO conjugate were investigated under different NaCl concentrations and pH levels. Mf became highly solubilized at lower NaCl concentrations by conjugation with AO, with a slight loss of available lysine. The thermal stability of Mf was effectively improved by conjugation with AO. Heat treatment at 80 degrees C for 2 h had no effect on the solubility of the Mf-AO conjugate attached to 227 microg/mg of AO regardless of the NaCl concentration and pH. Furthermore, the Mf-AO conjugate showed excellent emulsion-forming ability regardless of NaCl concentration. The improved functionalities of Mf by conjugation with AO remained even at a nearly isoelectric point. These results indicate that conjugation with AO through the Maillard reaction is an effective way to prepare high-functional food material from fish muscle protein.

Alginates↗
PubMed1998

Alginate beads as an affinity material for alpha amylases.

Calcium-alginate beads were found to bind a variety of enzymes in a nonspecific fashion. However, alpha amylases from porcine pancreas, Bacillus subtilis (BAN 240L) and wheat germ bound at a significant level and B. subtilis and wheat germ amylases could be eluted with 1M maltose. The wheat germ alpha amylase could be purified 45 fold with 70% recovery. The SDS-PAGE pattern showed significant purification by this single step strategy.

Alginates↗
PubMedDate not supplied

Evaluation of a new antiseptic-containing alginate impression material.

A comparison was made of the disinfection achieved in impressions taken in Blueprint Asept alginate impression material and those taken in the plain brand of this material disinfected by immersion in 1% Hycolin solution for one minute. The plain Blueprint impression material without disinfection was used as a control. Impressions were taken of dies which had been contaminated with 0.75 ml of saliva from each of 20 volunteers. The surfaces of the impressions were used to inoculate Wilkins-Chalgren agar plates immediately and after 1 and 2 hours' storage of the impressions. The number of organisms recovered from the surface of the Blueprint Asept impressions was 1.5% of the control immediately after removal from the dies and complete disinfection was observed within one hour. In contrast, the number of organisms recovered from the surface of the impressions disinfected with 1% Hycolin solution was 30% of the control immediately after disinfection, and viable organisms could still be recovered after 2 hours' storage. Blueprint Asept impression material appears, therefore, to provide a high degree of disinfection when compared with the plain material treated with 1% Hycolin solution for one minute.

Adult↗
PubMed2004

Purification of goat immunoglobulin G by immobilized metal-ion affinity using cross-linked alginate beads.

The alginate beads obtained by cross-linking of the polymer by epichlorohydrin were charged with Cu(II). The copper-charged beads could be directly used as a immobilized-metal-affinity-chromatographic medium for purification of goat IgG. The best results in the packed-bed mode were obtained by using beads charged with 95.4 micromol/ml Cu(II). We found that we could recover 97.4% IgG with an 8-fold purification.

Alginates↗
PubMed1975

The biosynthesis of alginic acid by Azotobacter vinelandii.

The sequence of reactions by which alginic acid is biosynthesized from sucrose in Azotobacter vinelandii was determined both by feeding radioactive individual enzymes involved. Results indicate that the first polymeric substance formed in the synthesis is polymannuronic acid and that mannuronic acid units are epimerized to guluronic acid at the polymer level. Guluronic acid does not appear to be formed at the monomer level, either free or in combination with GDP.

Alcohol Oxidoreductases↗
PubMed2000

Continuous production of lacticin 3147 and nisin using cells immobilized in calcium alginate.

Bacteriocinogenic strains, Lactococcus lactis subsp. lactis DPC 3147 and L. lactis DPC 496, producing lacticin 3147 and nisin, respectively, were immobilized in double-layered calcium alginate beads. These beads were inoculated into MRS broth at a ratio of 1:4 and continuously fermented for 180 h. Free cells were used to compare the effect of immobilization on bacteriocin production. After equilibrium was reached, a flow rate of 580 ml h(-1) was used in the immobilized cell (IC), and 240 ml h(-1) in free-cell (FC) bioreactors. Outgrowth from beads was observed after 18 h. Bacteriocin production peaked at 5120 AU ml(-1) in both IC and FC bioreactors. However, FC production declined after 80 h to 160 AU ml(-1) at the end of the fermentation. Results of this study indicate that immobilization offers the possibility of a more stable and long-term means of producing lacticin 3147 in laboratory media than with free cells.

Alginates↗
PubMed2001

pH-controlled cell release and biomass distribution of alginate-immobilized Lactococcus lactis subsp. lactis.

AIMS: To investigate the growth and release of Lactococcus lactis subsp. lactis in gel beads and to affect rates of cell release by changing the growth conditions. METHODS AND RESULTS: The rate of release and the distribution of immobilized L. lactis subsp. lactis in alginate beads were studied in continuous fermentations for 48 h. A change in operating pH from 6.5 to 9.25 initially reduced the ratio of the rates of cell release to lactate production by almost a factor of 105. Compared with fermentations at pH 6.5, growth at pH 9.25 also increased the final internal bead biomass concentration by a factor of 5 and increased the final rate of lactate production by 25%. After 48 h, the ratio of the rates of cell release to lactate production was still 10 times lower than in fermentations at pH 6.5. CONCLUSIONS: A change in the operating pH from 6.5 to 9.25 reduced rates of cell release throughout 48 h of fermentation and increased the final rates of lactate production and internal bead biomass concentration. SIGNIFICANCE AND IMPACT OF THE STUDY: These data illustrate that diffusional limitations and corresponding pH gradients can be exploited in affecting the distribution of immobilized growing cells and their concomitant release.

Alginates↗
PubMed1997

Setting properties of alginate impression materials in dynamic viscoelasticity.

The viscoelastic properties of three alginate impression materials were investigated. A landmark of working time was calculated using a raw phase-time curve. A landmark of setting time was calculated from an inflection point of the divided difference of the first order in the share modulus-time curve. As a result, the working time was common at the point of delta = 45 degrees in variable frequencies. The mean value was obtained with less deviation. The setting times obtained were similar for variable frequencies. The mean values showed a distinct difference for each impression material.

Alginates↗
PubMed2002

Effect of mixing method on rheological properties of alginate impression materials.

The apparent viscosity of alginate impression paste prepared by three mixing methods (hand-mixing technique (HM), semiautomatic instrument (SM) and automatic mixing instrument (AM)), and the gel strength and surface depression of the respective set materials were measured. The materials used were eight commercially available products mixed at a temperature of 23 +/- 0.5 degrees C and allowed to set. The AM had a high mixing speed, which reduced the working time 4.4-31.5%, compared with HM. This was the result of an increase in paste temperature during mixing. In the case of impression materials mixed with the AM, the gel strength and the surface depression at the gel fracture increased significantly, in accordance with Fisher's protected least significant difference (PLSD) analysis. This phenomenon is caused by a decrease of air bubbles in the set material.

Air↗
PubMed1998

Alginate, inorganic polyphosphate, GTP and ppGpp synthesis co-regulated in Pseudomonas aeruginosa: implications for stationary phase survival and synthesis of RNA/DNA precursors.

The regulatory protein AlgR2 in Pseudomonas aeruginosa positively regulates nucleoside diphosphate kinase (Ndk) and succinyl-CoA synthetase, enzymes critical in nucleoside triphosphate (NTP) formation. AlgR2 positively regulates the production of alginate, GTP, ppGpp and inorganic polyphosphate (poly P). An algR2 mutant with low levels of these metabolites has them restored by introducing and overexpressing either the algR2 or the ndk gene into the algR2 mutant. Thus, Ndk is involved in the formation of these compounds and largely prevents the death of the algR2 mutant, which occurs early in the stationary phase. We demonstrate that the 12 kDa Ndk-pyruvate kinase (Pk) complex, previously shown to generate predominantly GTP instead of all the NTPs, has a low affinity for the deoxynucleoside diphosphates and cannot generate the dNTPs needed for DNA replication and cell division; this complex may thus be involved in regulating the levels of both NTPs and dNTPs that modulate cell division and survival in the stationary phase.

Alginates↗
PubMed1999

Evaluation of modified alginate-chitosan-polyethylene glycol microcapsules for cell encapsulation.

A bioartificial pancreas, a medical device entrapping islets of Langerhans (islets) in an immunoisolative membrane, has been regarded as one of the most promising approaches to treat insulin-dependent diabetic patients. In this study, various modifications of alginate-chitosan microcapsules were made such as the inclusion of polyethylene glycol (PEG) and the use of crosslinkers such as carbodiimide (EDC) and glutaraldehyde (GA) in the core and onto the microcapsule membrane surface. A characterization of the modified microcapsules in terms of mechanical stability and albumin diffusion as well as their surface properties using SEM was performed. A mild GA treatment greatly enhanced the mechanical stability of the microcapsules, and this treatment did not affect the coating process of chitosan or PEG. The biological response to such microcapsules was evaluated by microencapsulation of red blood cells (RBC) and subsequent observation of their hemoglobin release. The encapsulated RBC in the PEG-GA coated microcapsules were found to be less hemolytic and had improved stability and biocompatibility. The results suggest the possibility of developing biological assist organs by microencapsulation of mammalian cells such as islets or liver cells in immunoisolative microcapsules in the near future.

Albumins↗
PubMed1998

Matrix degradation by chondrocytes cultured in alginate: IL-1 beta induces proteoglycan degradation and proMMP synthesis but does not result in collagen degradation.

OBJECTIVE: To determine the role of interleukin-1 beta (IL-1 beta) in the degradation of proteoglycans and collagen by articular chondrocytes. DESIGN: Chondrocytes were cultured in alginate beads for 2 weeks to produce extracellular matrix, followed by the addition of IL-1 beta for 1 or 2 days. Breakdown of extracellular matrix (with and without activation of pro-matrix metalloproteinases (MMPs) by APMA) was monitored by release of glycosaminoglycans (GAG, proteoglycans) and hydroxyproline (collagen) from the beads into the medium, and by the amount of damaged collagen in the bead. Levels of (pro)MMPs in the beads were assayed by zymography and their activity was quantified fluorometrically. RESULTS: IL-1 beta induced a profound GAG release (approximately 80% after 2 days at 20 ng/ml IL-1 beta) that was both time and IL-1 beta concentration dependent. Under these conditions no increase in collagen release or damaged collagen in the bead was detected. Zymography demonstrated that the synthesis of a variety of proMMPs was induced by IL-1 beta, without a detectable increase of MMP-activity as measured in the activity assay. After activation of the proMMPs by APMA, a time and IL-1 beta concentration-dependent increase in MMP-activity was found, which resulted in almost complete deterioration of collagen already after 18 h of incubation. In the presence of APMA, GAG release from IL-1 beta treated beads was significantly increased from 24 to 31%. CONCLUSIONS: Our data suggest that proteoglycan and collagen degradation are regulated through different mechanisms: IL-1 beta induces the synthesis of active enzymes that degrade proteoglycans, such as 'aggrecanase', and inactive proMMPs. Thus, IL-1 beta alone is not sufficient to result in collagen-degrading MMPs. Once activated, MMPs may account for up to a quarter of the aggrecan degradation in this model.

Alginates↗
PubMed2002

Treatment of soft tissue defects with exposed bone in the head and face region with alginates and hydrocolloid dressings.

PURPOSE: In cases of soft tissue defects with exposed bone surfaces in the head and face region, there is the option of treating the defect with free split-thickness skin grafts following appropriate wound granulation. Secondary granulation on free bone surfaces is often a lengthy process, as granulation primarily occurs from the edges of the wound. Hydrocolloid dressings are gaining increasing attention in this context. The question arises as to whether the positive properties of hydrocolloid dressings can bring about rapid and positive conditioning of the base of the wound in soft tissue defects with exposed bone in the head and face region, with a view to subsequent split-thickness skin graft transplantation. MATERIALS AND METHODS: In the period from 1997 to 2000, a total of 25 patients with soft tissue defects with exposed bone surfaces in the head and face region were treated with hydrocolloid dressings in the framework of a prospective clinical study. RESULTS: The average time taken for complete granulation of the bone surface was 39.44 days (minimum, 10 days; maximum, 72 days). As a rule, this necessitated 12.8 changes of dressing (minimum, 3; maximum, 26). The granulation tissue was of good quality, generously vascularized, and occasionally exuberant at the edges of the wound CONCLUSION: On the whole, the combination of hydrocolloid dressing and alginate compress was found to have significant advantages as regards conditioning the exposed bone surface.

Adult↗
PubMed2002

Comparison of calcium alginate film with collagen membrane for guided bone regeneration in mandibular defects in rabbits.

PURPOSE: We sought to compare calcium alginate film (CAF) with collagen membrane (CM) regarding their effects on guided bone regeneration. MATERIALS AND METHODS: Circular bone defects with 5-mm diameter were created in the region anterior to both mandibular angles in 34 rabbits. The defects on one side were covered with a CAF, and the contralateral side with CM. Healing condition was analyzed with gross, radiographic, electromicroscopic, histologic, and immunohistochemical studies and image pattern analysis system after 1, 2, 4, 6, and 8 weeks. RESULTS: CM absorbed more slowly but collected fewer osteoinductive factors (P <.05) in the early period. CAF induced dense bone formation, whereas CM produced less newly formed bone. CONCLUSION: CAF is more efficacious than CM in guided bone regeneration in this animal model.

Alginates↗