|Articles about Biomaterials|
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| Adverse effect of staphylococci slime on in vitro activity of glycopeptides
Mathur, T., S. Singhal, et al. (2005), Jpn J Infect Dis 58(6): 353-7.
Abstract: Adhesion to biomaterial is assumed to be a crucial step in the development of staphylococcal foreign body infections. Production of extracellular slime has major implications for the development and implementation of therapeutic strategies. The effect of extracted slime was investigated on the activity of vancomycin, teicoplanin, linezolid, quinupristin/dalfopristin, rifampicin and ranbezolid against 10 clinical and 4 ATCC staphylococcal isolates. The slime extract caused a 2- to 16-fold increase in the MICs of vancomycin and teicoplanin, with a shift in the MIC(90) from 2 to 32 (vancomycin) and 2 to 16 (teicoplanin), whereas the MICs of linezolid and quinupristin/dalfopristin were only moderately affected. In time-kill studies, a significant decrease in bacterial killing (>3 log(10) cfu/ml) was observed with vancomycin and teicoplanin (4X MIC) after addition of slime (5 and 20 mg/ml), whereas the effect of killing by linezolid and quinupristin/dalfopristin was very modest. The rifampicin and ranbezolid MICs and kill curves were not influenced by the addition of slime. The present study thus indicated that slime interferes with the antimicrobial effect of glycopeptide drugs (vancomycin, teicoplanin), and that for effective prevention and treatment of prosthetic device-related infections, appropriate and newer antibiotics such as ranbezolid should be considered.
| Adverse events of sutures: possible interactions of biomaterials?
Holzheimer, R. G. (2005), Eur J Med Res 10(12): 521-6.
Abstract: Absorbable sutures are in use for more than 30 years. Tissue reactions which might be associated with suture material have rarely been reported in the past. After a long period without complications caused by suture material we observed 12 cases of unexpected tissue reactions after clean operations. Our patients 3-8 weeks after uneventful elective clean operations (varicose vein, hernia, benign soft tissue tumor) had unexpected tissue reactions (inflammation, granuloma, extrusion, fistula, abscess) in the vicinity of Vicryl (R), suture material (8 cases with Vicryl (R), 4 cases with Vicryl plus (R)). After removal of the suture material and the granulomatous tissue wounds healed without any further disturbance. These tissue reactions have been observed in patients with subcuticular sutures as well as in patients with deeper located vein ligatures. It is well known that next to patient-associated and surgeon-related factors biomaterials might have an impact on postoperative inflammatory process and healing. We use Vicryl (R), suture material for ambulatory surgery since 1999 and did not see complications for a long period up to now. 11 of the patients were observed within several weeks in summer 2005, whereas only one patient has been observed in the year 2004. All 11 patients observed in 2005 had a combination of Vicryl (R)/ Vicryl plus (R) suture material in deep/subcutaneous and Dermabond (R) glue for skin closure. - We do not know the cause for this change. For clarification evaluation of the tissue reactions of these biomaterials including possible interactions or combined reactions should be done.
| Adverse reactions to injectable soft tissue permanent fillers
Christensen, L., V. Breiting, et al. (2005), Aesthetic Plast Surg 29(1): 34-48.
Abstract: BACKGROUND: Synthetic injectable facial fillers with a permanent effect are widely atoxic and nonimmunogenic, but they differ with respect to composition and in chemical and biologic characteristics. Yet, they all act as foreign bodies in the tissues eliciting a host response that try to remove the gel. Inflammatory nodules may develop at the sites of injection-for some fillers, many years later, for others, not. Why is that? METHODS: Biopsies were contributed by various plastic surgeons from Europe and Australia after requests were made at international congresses and workshops. The study was based on (a) 5 biopsies from unreactive tissue obtained at different times after injection of polyacrylamide hydrogel (Aquamid); (b) 28 biopsies from intermediate or late inflammatory nodules after injection of polyacrylamide hydrogel (Aquamid) (20 cases), a hyaluronic acid-polyhydroxyethylmethacrylate/ethylmethacrylate gel (Dermalive) (2 cases), and a gel consisting of polylactic acid in mannitol/carbomethoxycellulose (New-Fill) (6 cases); and (c) a review of the literature on adverse reactions after injection with permanent fillers. RESULTS: Clinically unreactive tissues after injection with Aquamid showed modest or no host reaction. Inflammatory nodules showed an increased foreign body reaction and a bacterial infection after injection with Aquamid, and a combination of moderate foreign body reaction, fibrosis, and in some cases also bacterial infection after injection with Dermalive and New-Fill. According to the literature, inflammatory nodules occur no later than 1 year after injection with polyacrylamide hydrogel, but up to 6 years after injection of combination gels (Artecol), and up to 28 years after injection of silicone gel. CONCLUSIONS: Inflammatory nodules are likely to be caused by a low-grade infection maintained within a biogfilm surrounding the hydrophobic silicone gel and the combination gels. Aquamid gel may prevent formation of a biofilm through its high water-binding capacity, explaining why late inflammatory nodules are not seen after injection of this polyacrylamide hydrogel product.
| AFM imaging of ligand binding to platelet integrin alphaIIbbeta3 receptors reconstituted into planar lipid bilayers
Hussain, M. A., A. Agnihotri, et al. (2005), Langmuir 21(15): 6979-86.
Abstract: The platelet integrin alphaIIbbeta3 plays a key role in platelet adhesion, activation, and aggregation at the subendothelium and at protein-coated synthetic biomaterials. In this study, interactions between alphaIIbbeta3 and both protein and peptide ligands for the receptor were imaged under physiological conditions by high-resolution atomic force microscopy (AFM). To directly image the ligand-receptor interactions, alphaIIbbeta3 receptors were reconstituted into a supported lipid bilayer formed on a mica surface in the AFM fluid cell assembly and subsequently activated with Mn2+. Fibrinogen, the natural protein ligand for the integrin, as well as a nanogold-labeled peptide ligand (an RGD-containing heptamer) were infused into the AFM fluid cell, incubated with the reconstituted and activated receptors, and imaged under buffer. Height images illustrating topographical features showed the integrin reconstituted in the bilayer. Fibrinogen molecules binding to the receptors were easily observed in the height images, with fibrinogen showing its characteristic trinodular structure and occasionally bridging integrin receptors. Fibrinogen was observed to bind to integrins at the D-domain consistent with the location of the gamma-chain dodecapeptide, while fibrinogen bridging integrins bound to receptors on opposite sides of the protein consistent with a 2-fold axis of symmetry. Peptide ligands were not visible in height images; however, phase images that map the mechanical properties detected the nanogold labels and demonstrated the presence of peptide ligands bound to the receptors. The results demonstrate the ability of this high-resolution microscopy technique to directly visualize single ligand/receptor interactions in a dynamic and physiologically relevant environment, and establish a framework for future fundamental studies of single protein/receptor interactions during normal pathological processes as well as biomaterial surface-induced thrombosis.
| Aging and microwave effects on alginate/chitosan matrices
Wong, T. W., L. W. Chan, et al. (2005), J Control Release 104(3): 461-75.
Abstract: The influence of microwave irradiation on the drug release properties of freshly prepared and aged alginate, alginate-chitosan and chitosan beads was investigated. The beads were prepared by extrusion method with sulphathiazole as a model drug. The dried beads were subjected to microwave irradiation at 80 W for 10 min, 20 min or three consecutive cycles of 10 and 20 min, respectively. The profiles of drug dissolution, drug content, drug stability, drug polymorphism, drug-polymer interaction, polymer crosslinkage and complexation were determined by dissolution testing, drug content assay, differential scanning calorimetry and Fourier transform infra-red spectroscopy. The chemical stability of drug embedded in beads was unaffected by microwave conditions and length of storage time. The release property of drug was mainly governed by the extent of polymer interaction in beads. The aged alginate beads required intermittent cycles of microwave irradiation to induce drug release retarding effect in contrast to their freshly prepared samples. Unlike the alginate beads, the level of polymer interaction was higher in aged alginate-chitosan beads than the corresponding fresh beads. The drug release retarding property of aged alginate-chitosan beads could be significantly enhanced through subjecting the beads to microwave irradiation for 10 min. No further change in drug release from these beads was observed beyond 30 min of microwave irradiation. Unlike beads containing alginate, the rate and extent of drug released from the aged chitosan beads were higher upon treatment by microwave in spite of the higher degree of polymer interaction shown by the latter on prolonged storage. The observation suggested that the response of polymer matrix to microwave irradiation in induction of drug release retarding property was largely affected by the molecular arrangement of the polymer chains.
| Akt1 regulates pathological angiogenesis, vascular maturation and permeability in vivo
Chen, J., P. R. Somanath, et al. (2005), Nat Med 11(11): 1188-96.
Abstract: Akt kinases control essential cellular functions, including proliferation, apoptosis, metabolism and transcription, and have been proposed as promising targets for treatment of angiogenesis-dependent pathologies, such as cancer and ischemic injury. But their precise roles in neovascularization remain elusive. Here we show that Akt1 is the predominant isoform in vascular cells and describe the unexpected consequences of Akt1 knockout on vascular integrity and pathological angiogenesis. Angiogenic responses in three distinct in vivo models were enhanced in Akt1(-/-) mice; these enhanced responses were associated with impairment of blood vessel maturation and increased vascular permeability. Although impaired vascular maturation in Akt1(-/-) mice may be attributed to reduced activation of endothelial nitric oxide synthase (eNOS), the major phenotypic changes in vascular permeability and angiogenesis were linked to reduced expression of two endogenous vascular regulators, thrombospondins 1 (TSP-1) and 2 (TSP-2). Re-expression of TSP-1 and TSP-2 in mice transplanted with wild-type bone marrow corrected the angiogenic abnormalities in Akt1(-/-) mice. These findings establish a crucial role of an Akt-thrombospondin axis in angiogenesis.
| Albumin binding surfaces for biomaterials
Keogh, J. R. and J. W. Eaton (1994), J Lab Clin Med 124(4): 537-45.
Abstract: The surfaces of medical devices may promote both coagulation and infections caused by adherent microorganisms. In the case of polymeric elastomers, these iatrogenic effects are likely intermediated by absorbed host proteins that spontaneously bind to the device surface, promoting both bacterial adherence and thrombotic events. We earlier attempted to produce biomaterial surfaces that would selectively bind host albumin because albumin-coated surfaces were known to diminish both coagulation and bacterial adherence. To this end, an albumin-binding high molecular weight dextran:Cibacron blue adduct was bulk incorporated into polyetherurethane (Keogh et al., J Biomed Mater Res 1992;26:441). The modified material bound albumin selectively and reversibly and showed evidence of enhanced biocompatibility. However, approximately 30% of the surface of this material was evidently unmodified and still capable of exerting the above adverse effects. In the present work, we have covalently surface-modified polyetherurethane with sequential additions of acrylamide, amino-propylmethacrylamide, dextran, and Cibacron blue. This derivatized polyurethane preferentially and reversibly binds albumin, even from complex mixtures of proteins such as plasma. Furthermore, this material inhibits the clotting of nonanticoagulated whole human blood (for > 16 hours at room temperature), perhaps by virtue of binding and activation of antithrombin III by the sulfonic acid residues on the surface-immobilized Cibacron blue. Finally, such surfaces, especially when bearing bound albumin, diminish the adherence of Staphylococcus epidermidis, a pathogen frequently associated with device-centered infections. We conclude that similar albumin-affinity surfaces may hold promise for the development of more biocompatible materials for implantation and blood contact applications.
| Al-Cu-Fe quasicrystal/ultra-high molecular weight polyethylene composites as biomaterials for acetabular cup prosthetics
Anderson, B. C., P. D. Bloom, et al. (2002), Biomaterials 23(8): 1761-8.
Abstract: Polymer composites of Al-Cu-Fe quasicrystals and ultra-high molecular weight polyethylene (UHMWPE) were investigated for use in acetabular cup prosthetics. The wear properties of the Al-Cu-Fe/UHMWPE samples and a 440 steel ball counterface were measured. The mechanical strength of the Al-Cu-Fe/UHMWPE composites was compared to UHMWPE and alumina/UHMWPE. The biocompatibility of the composite material was tested using a direct contact cytotoxicity assay. Al-Cu-Fe/UHMWPE demonstrated lower volume loss after wear and higher mechanical strength than UHMWPE. This composite material also showed no increase in counterface wear or cytotoxicity relative to UHMWPE. These combined results demonstrate that Al-Cu-Fe/UHMWPE composites are promising candidate materials for acetabular cup prosthetics.
| Alginate acetylation influences initial surface colonization by mucoid Pseudomonas aeruginosa
Tielen, P., M. Strathmann, et al. (2005), Microbiol Res 160(2): 165-76.
Abstract: Mucoid strains of Pseudomonas aeruginosa overproduce the exopolysaccharide alginate, which is substituted with O-acetyl groups. Under non-growing conditions in phosphate buffer, a mucoid clinical strain formed microcolonies on steel surfaces, while an acetylation-defective mutant was unable to form cell clusters. Enzymatic degradation of alginate by alginate lyase prevented microcolony formation of the mucoid parent strain. In a continuous-culture flow-cell system, using gluconate minimal medium, the mucoid strain with acetylated alginate formed microcolonies and grew into heterogenous biofilms, whereas the acetylation-defective mutant produced a thinner and more homogeneous biofilm. A lowered viscosity of extracellular material from the acetylation-defective mutant indicated a weakening of exopolymer interactions by loss of acetyl groups. These results suggest that acetyl substituents are necessary for the function of high-molecular-mass alginate to mediate cell aggregation into microcolonies in the early stages of biofilm development by mucoid P. aeruginosa, thereby determining the architecture of the mature biofilm.
| Alginate and chitosan polyion complex hybrid fibers for scaffolds in ligament and tendon tissue engineering
Majima, T., T. Funakosi, et al. (2005), J Orthop Sci 10(3): 302-7.
Abstract: Selecting the material for a scaffold is critically important for the success of tissue engineering. To simplify complicated biosynthetic matrices and achieve a novel class of potential materials, a model of polyion complex fibers was prepared from alginate and chitosan. In the current in vitro study, we thought that alginate-based chitosan hybrid biomaterials could provide excellent supports for fibroblast adhesion. In the current study, alginate polymer fiber (alginate group) and alginate-based chitosan hybrid polymer fibers (alginate with 0.05% chitosan, alginate-chitosan 0.05% group; alginate with 0.1% chitosan, alginate-chitosan 0.1% group) were originally prepared. We investigated the adhesion behavior of rabbit tendon fibroblast onto alginate polymer fibers versus the adhesion of the fibroblast onto alginate-based chitosan hybrid polymer fibers. Furthermore, mechanical properties and synthesis of the extracellular matrix were investigated. Mechanically, the novel fiber has considerable tensile strength of more than 200 MPa. We demonstrated that the alginate-based chitosan hybrid polymer fibers showed much improved adhesion capacity with fibroblast compared with alginate polymer fiber. Additionally, morphologic studies revealed the dense fiber of the type I collagen produced by the fibroblast in the hybrid polymer fibers. We concluded that an alginate-based chitosan hybrid polymer fiber has considerable potential as a desirable biomaterial scaffold for tendon and ligament tissue engineering.
| Alginate as a new biomaterial for the growth of porcine retinal pigment epithelium
Eurell, T. E., D. R. Brown, et al. (2003), Vet Ophthalmol 6(3): 237-43.
Abstract: OBJECTIVE: Determine the effect of a 3-dimensional alginate matrix on the growth and differentiation of cells isolated from porcine retinal pigment epithelium (RPE). PROCEDURES: Porcine RPE cells were harvested from enucleated eyecups, isolated by differential gravity sedimentation and cultured in either alginate alone (Group 1) or on plastic tissue culture plates followed by alginate (Group 2). Group 1 cells were cultured in alginate to evaluate the efficacy of the matrix as a culture medium. Group 2 cells were initially cultured on plastic to induce dedifferentiation. The cells were then harvested, suspended in alginate beads, and incubated for a second culture period to determine if the induced dedifferentiation was reversible. RESULTS: The number of Group 1 cells was significantly greater (P < or = 0.01) at the end of the culture period. The amount of pigment and cell morphology of Group 1 cells at the end of the culture period was similar to that seen at initial cell isolation. The initial culture of Group 2 cells on plastic showed characteristic features of dedifferentiation marked by the loss of pigment and alterations in microscopic appearance. Secondary culture of dedifferentiated Group 2 cells in alginate beads resulted in a return to pigmentation and characteristic morphology for a majority of the cultured cells. CONCLUSIONS: Porcine RPE cells can be propagated in alginate culture with a significant increase in cell numbers while maintaining normal morphology. Under the conditions described in the present study, the dedifferentiation of porcine RPE induced by standard in vitro culture methods is reversible.
| Alginate as an auxiliary bacterial membrane: binding of membrane-active peptides by polysaccharides
Chan, C., L. L. Burrows, et al. (2005), J Pept Res 65(3): 343-51.
Abstract: The chronicity of Pseudomonas aeruginosa infections in cystic fibrosis (CF) patients is characterized by overproduction of the exopolysaccharide alginate, in which biofilm bacteria are embedded. Alginate apparently contributes to the antibiotic resistance of bacteria in this form by acting as a diffusion barrier to positively charged antimicrobial agents. We have been investigating cationic antimicrobial peptides (CAPs) (prototypic sequence: KKAAAXAAAAAXAAWAAXAAAKKKK-NH(2), where X is any of the 20 commonly occurring amino acids) that were originally designed as transmembrane mimetic peptides. Peptides of this group above a specific hydrophobicity threshold insert spontaneously into membranes and have antibacterial activity at micromolar concentrations. While investigating the molecular basis of biofilm resistance to peptides, we found that the anionic alginate polysaccharide induces conformational changes in the most hydrophobic of these peptides typically associated with insertion of such peptides into membrane environments [Chan et al., J. Biol. Chem. (2004) vol. 279, pp. 38749-38754]. Through a combination of experiments measuring release of the fluorescent dye calcein from phospholipid vesicles, peptide interactions with vesicles in the presence and absence of alginate, and affinity of peptides for alginate as a function of net peptide core hydrophobicity, we show here that alginate offers a microenvironment that provides a protective mechanism for the encased bacteria by both binding and promoting the self-association of the CAPs. The overall results indicate that hydrophilic alginate polymers contain a significant hydrophobic compartment, and behave as an 'auxiliary membrane' for bacteria, thus identifying a unique protective role for biofilm exopolysaccharide matrices.
| Alginate assessment by NMR microscopy
Grant, S. C., S. Celper, et al. (2005), J Mater Sci Mater Med 16(6): 511-4.
Abstract: Alginate hydrogels have long been used to encapsulate cells for the purpose of cell transplantation. However, they also have been criticized because they fail to consistently maintain their integrity for extended periods of time. Two issues of critical importance that have yet to be thoroughly addressed concerning the long-term integrity of alginate/poly-L-lysine/alginate microcapsules are: (i) are there temporal changes in the alginate/poly-L-lysine interaction and (ii) are there temporal changes in the alginate gel structure. NMR microscopy is a non-invasive analytical technique that can address these issues. in this report, we present data to demonstrate the utility of (1)H NMR microscopy to (i) visualize the poly-L-lysine layer in an effort to address the first question, and (ii) to observe temporal changes in the alginate matrix that may represent changes in the gel structure.
| Alginate beads as immobilization matrix for hepatocytes perfused in a bioreactor: a physico-chemical characterization
Murtas, S., G. Capuani, et al. (2005), J Biomater Sci Polym Ed 16(7): 829-46.
Abstract: Because of their peculiar physico-chemical properties, alginate beads have often been proposed as an alternative cell immobilization matrix for many biotechnological applications. For entrapped hepatocytes perfused in a bioreactor, alginate beads have been demonstrated to promote viability and three-dimensional cell organization. In order to optimise the hepatocyte cell culture, we investigated the relationship between alginate beads properties, at high and low content of guluronic acid (G), and the relative cell viability and reorganization when perfused in a bioreactor. The primary structure of alginates did not apparently influence the hepatocytes culture in 8 h of perfusion in a bioreactor. However, our results confirm a preference for beads with a high content of G due to their superior mechanical resistance.
| Alginate lyase (AlgL) activity is required for alginate biosynthesis in Pseudomonas aeruginosa
Albrecht, M. T. and N. L. Schiller (2005), J Bacteriol 187(11): 3869-72.
Abstract: To determine whether AlgL's lyase activity is required for alginate production in Pseudomonas aeruginosa, an algLdelta:Gm(r) mutant (FRD-MA7) was created. algL complementation of FRD-MA7 restored alginate production, but algL constructs containing mutations inactivating lyase activity did not, demonstrating that the enzymatic activity of AlgL is required for alginate production.
| Algipore sandwiches or alveolar distraction? Re: Ewers R, Fock N, Millesi-Schobel G, Enislidis G. Pedicled sandwich plasty: a variation on alveolar distraction for vertical augmentation of the atrophic mandible. Br J Oral Maxillofac Surg 2004;42:445-7
Garcia, A. G., M. Somoza-Martin, et al. (2005), Br J Oral Maxillofac Surg 43(5): 438; author reply 439.
| Aligned two- and three-dimensional structures by directional freezing of polymers and nanoparticles
Zhang, H., I. Hussain, et al. (2005), Nat Mater 4(10): 787-93.
Abstract: The preparation of materials with aligned porosity in the micrometre range is of technological importance for a wide range of applications in organic electronics, microfluidics, molecular filtration and biomaterials. Here, we demonstrate a generic method for the preparation of aligned materials using polymers, nanoparticles or mixtures of these components as building blocks. Directional freezing is used to align the structural elements, either in the form of three-dimensional porous structures or as two-dimensional oriented surface patterns. This simple technique can be used to generate a diverse array of complex structures such as polymer-inorganic nanocomposites, aligned gold microwires and microwire networks, porous composite microfibres and biaxially aligned composite networks. The process does not involve any chemical reaction, thus avoiding potential complications associated with by-products or purification procedures.
| Aliphatic polyesters: great degradable polymers that cannot do everything
Vert, M. (2005), Biomacromolecules 6(2): 538-46.
Abstract: Nowadays the open and the patent literatures propose a large number of polymers whose main chains can be degraded usefully. Among these degradable polymers, aliphatic polyester-based polymeric structures are receiving special attention because they are all more or less sensitive to hydrolytic degradation, a feature of interest when compared with the fact that living systems function in aqueous media. Only some of these aliphatic polyesters are enzymatically degradable. A smaller number is biodegradable, and an even more limited number is biorecyclable. To be of practical interest, a degradable polymer must fulfill many requirements that depend very much on the targeted application, on the considered living system, and on living conditions. It is shown that aliphatic polyester structures made of repeating units that can generate metabolites upon degradation or biodegradation like poly(beta-hydroxy alkanoate)s and poly(alpha-hydroxy alkanoate)s are of special interest. Their main characteristics are confronted to the specifications required by various potential sectors of applications, namely, surgery, pharmacology, and the environment. It is shown that degradation, bioresorption, and biorecycling that are targets when one wants to respect living systems are also drastic limiting factors when one wants to achieve a device of practical interest. Finding a universal polymer that would be the source of all the polymeric biomaterials needed to work in contact with living organisms of the various life kingdoms and respect them remains a dream. On the other hand, finding one polymeric structure than can fulfill the requirements of one niche application remains a big issue.
| Alkaline phosphatase encapsulated in gellan-chitosan hybrid capsules
Fujii, T., D. Ogiwara, et al. (2005), Macromol Biosci 5(5): 394-400.
Abstract: Alkaline phosphatase (ALP) was encapsulated in gellan-chitosan polyion complex (PIC) capsules using a convenient procedure. The recovery of ALP was about 50% when the capsules were prepared by dropping a solution of ALP and gellan mixture (ALP/gellan) into a chitosan solution. When p-nitrophenyl phosphate (p-NPP) and 5-bromo-4-chloro-3-indolyl phosphate (BCIP) were incubated with ALP/gellan-chitosan capsules as substrates for ALP, the transparent colorless capsules changed to yellow and blue, respectively. The encapsulation of ALP into the PIC capsules was also confirmed by SDS-PAGE and immunoblot analyses. The ALP and polypeptides of more than 30 kDa remained without release even after incubation at 4 degrees C for 14 d. The biochemical properties of the encapsulated ALP activity were similar to those of the intact enzyme. When the solution containing p-NPP was loaded on a column packed with ALP/gellan-chitosan capsules at 27 degrees C, approximately 75% of p-NPP was hydrolyzed by passing through the column. No significant leakage of ALP was observed during the procedure, indicating that the capsules were resistant to pressure in the chromatographic operation. Furthermore, 70% of the hydrolytic activity of the packed capsules remained after storage at 4 degrees C for one month. These results suggest that the polyion complex capsules could be useful materials for protein fixation without chemical modification. [Diagram: see text] Encapsulation of ALP into PIC capsules and the morphological changes seen in the absence of the ALP substrate and in the presence of p-NPP and BICP.
| Alkaline protease production by an isolated Bacillus circulans under solid-state fermentation using agroindustrial waste: process parameters optimization
Prakasham, R. S., C. Subba Rao, et al. (2005), Biotechnol Prog 21(5): 1380-8.
Abstract: Alkaline protease production using isolated Bacillus circulans under solid-state fermentation environment was optimized by using Taguchi orthogonal array (OA) experimental design (DOE) methodology to understand the interaction of a large number of variables spanned by factors and their settings with a small number of experiments in order to economize the process optimization. The software-designed experiments with an OA worksheet of L-27 was selected to optimize fermentation (temperature, particle size, moisture content and pH), nutrition (yeast extract and maltose), and biomaterial-related (inoculum size and incubation time) factors for the best production yields. Analysis of experimental data using Qualitek-4 methodology showed significant variation in enzyme production levels (32,000-73,000 units per gram material) and dependence on the selected factors and their assigned levels. Validation of experimental results on alkaline protease production by this bacterial strain based on DOE methodology revealed 51% enhanced protease production compared to average performance of the fermentation, indicating the importance of this methodology in the evaluation of main and interaction effects of the selected factors individually and in combination for bioprocess optimization.
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