Ionotropic alginate beads for controlled intestinal protein delivery: Effect of chitosan and barium counter-ions on entrapment and release

Alginate beads containing the model protein haemoglobin (Hb) were prepared by coagulation with various counter-ions to improve the controlled release of the protein. The effect of Ba(2+) and Ca(2+) ions and of the polycationic polysaccharide chitosan was investigated. Coagulation with Ba(2+), Ca(2+) and/or chitosan showed differences in the swelling index of the beads, in the encapsulation efficiency of Hb entrapment and in the release of the entrapped protein. Chitosan in the coagulation fluid markedly enhanced the encapsulation efficiency of the Hb. Release studies were conducted in simulated gastric fluid (SGF pH approximately or equal to 1.2) and subsequently in simulated intestinal fluid (SIF ) at 37 degrees C. Beads were stable in the gastric fluid but released their protein upon transfer to intestinal fluid. The release coincides with the burst and disintegration of beads. Rate of protein release from the beads was affected by the Ba(2+) and chitosan concentration in coagulation fluid.

Piggery wastewater treatment in a tropical climate: biological and chemical treatment options

A novel biological treatment system was developed for the treatment of piggery wastewater under tropical conditions. It consisted of three consecutive sponge-based floating biofilters. The Upflow Anaerobic/Anoxic/Aerobic Floating Filter (UA3FF) system was shown to be effective with carbonaceous and, particularly, nitrogenous matter. The rationale for the processes occurring in anoxic-aerobic reactors was based on the concept of nitritation-denitritation rather than nitrification-denitrification. The N-related microbial communities manipulated by changing DO concentration and hydraulic retention time were able to effect a considerable increase in the total and specific N-removal (70% and 0.6 kg N m(-3) filter media per day, respectively) as compared to data reported elsewhere. Fluorescence In Situ Hybridization and Polymerase Chain Reaction amplification of ammonia monooxygenase (amoA) gene were used to study interrelationships between N-related microbial groups in the system. Microbiological data was interpreted in terms of operational behavior and performance of the reactors. The N-removal efficiency of the biological UA3FF system was compared with a combined biological/physicochemical system based on (a) biological anaerobic pretreatment followed by (b) a chemical precipitation (CP) and (c) an air stripping. Both systems were scrutinized as to operational advantages and costs. The treatment options could produce effluent of a high quality (202 mg COD l(-1), 126 total-N l(-1) and 89 mg COD l(-1) 48 total-N l(-1) in the biological and combined biological/physico-chemical treatment options, respectively) amenable for the subsequent treatment at the municipal facilities. However, the UA3FF biological treatment system was superior to the combined system by a factor of 20 as far as costs are concerned.

Ionotropic cross-linked chitosan microspheres for controlled release of ampicillin

The solubility of non cross-linked chitosan in weak acid solutions restricts its utility in microspheres for drug delivery. The primary aim of this study was to produce pentasodium tripolyphosphate cross-linked chitosan microspheres with higher acid resistance for controlled release of ampicillin. The microspheres were prepared by two different microencapsulation procedures (by emulsification and by spray-drying) and characterized by their particle size, surface morphology, stability, drug entrapment efficiency and drug release. The size of the microspheres was <10 microm with a narrow size distribution. The entrapment of ampicillin in the microspheres was more than 80%. Stability of uncross-linked and cross-linked microspheres was affected by the pH of simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.5). The inclusion of the enzymes pepsin and pancreatin did not affect the stability of the microspheres. The inclusion of lysozyme in phosphate buffer saline resulted in increased solubilization. The release of the drug was affected by cross-linking of microspheres with tripolyphosphate (TPP). The cross-linked microspheres were more stable in simulated gastric fluid and showed slower but sustained release of ampicillin. The antimicrobial activity of the released ampicillin was confirmed by Staphylococcus aureus bioassay.

Peripheral enzymatic deacetylation of chitin and reprecipitated chitin particles

The enzymatic deacetylation of various chitin preparations was investigated using the fungal chitin deacetylase (CDA) isolated from Rhizopus oryzae growth medium. Specific extracellular enzyme activity after solid state fermentation was 10 times higher than that after submerged fermentation. Natural crystalline chitin is a very poor substrate for the enzyme, but showed a five-time better deacetylation after dissolution and reprecipitation. Chitin particles, enzymatically deacetylated for only 1% exhibited a strongly increased binding capacity towards ovalbumin, while maintaining the rigidity and insolubility of chitin in a moderate acidic environment. Because of the unique combination of properties, these CDA treated chitin materials were named "chit-in-osan". Chitinosan was shown to be an attractive matrix for column chromatography because no hydrogel formation was observed, that impaired the flow of eluent. Under the same conditions, partially deacetylated chitosan swelled and blocked the flow in the column.

Functional characteristics of shrimp chitosan and its membranes as affected by the degree of deacetylation

The functional properties of three shrimp chitosan preparations with different degrees of deacetylation (75%, 87% and 96% DD) but with a constant molecular weight (about 810 kDa) were investigated. Chitosan with 75% DD had a 1.5 times higher water absorption, probably due to its 20% lower level of crystallinity. Membranes cast from this chitosan also exhibited 1.5 times more water absorption and 2 times higher permeability. However, chitosan with 87% and 96% DD had 1.5-2 times higher absorption of fat and the orange II dye. This is attributed to the higher content of positively charged amine groups in the polymer. Cast into membrane, chitosan of higher degree of deacetylation showed a higher tensile strength and a higher elongation at break, probably due to the higher level of crystallinity.

Chitosan-alginate multilayer beads for controlled release of ampicillin

The aim of this study is to develop multilayer beads with improved properties for controlled delivery of the antibiotic ampicillin. Ionotropic gelation was applied to prepare single and multilayer beads using various combinations of chitosan and Ca(2+) as cationic components and alginate and polyphosphate as anions. Beads prepared with higher concentrations of chitosan entrapped more ampicillin. During incubation in simulated gastric fluid, the beads swelled and started to float but did not show any sign of erosion. Single layer chitosan-alginate beads released 70% of the drug within 4 h. Multilayer beads released only 20-30% in the same period of time. During subsequent incubation in simulated intestinal fluid, both single and multilayer beads continued to release drug. At least part of this release is due to disintegration of the beads. The rate of release both in gastric and intestinal fluid and the kinetics of disintegration in intestinal fluid can be controlled by changing the chitosan concentration in the coagulation fluid. The release of the drug can also be controlled by the degree of cross-linking using polyphosphate. Cross-linked multilayer beads were prepared that released only 40% of the entrapped drug during 24 h. It is concluded that chitosan-alginate multilayer beads, cross-linked with polyphosphate offer an opportunity for controlled gastrointestinal passage of compounds with low molecular weight like ampicillin.

Evaluation of an improved acid hydrolysis-HPLC assay for the acetyl content in chitin and chitosan

Functional properties of the amino polysaccharides, chitin and chitosan, vary significantly with their acetyl content. The acid hydrolysis-HPLC method offers good accuracy and precision to assay the acetyl content regardless of the solubility of the sample. In this research, the hydrolysis parameters were changed, and the analytical method was counterchecked with other methods. Complete hydrolysis was achieved by mixing chitosan with 1.4 mM oxalic acid and 12 M sulfuric acid followed by treatment at 110 degrees C for 40 min. A sealed glass ampule was used instead of a vacuum hydrolysis tube. The acetic acid released during acid hydrolysis was measured quantitatively by HPLC. A high correlation (r(2) = 0.98) was obtained between the modified HPLC assay and the solid-state (13)C CP/MAS NMR method for the samples of various crustacean sources with a wide range of acetyl contents. The modified HPLC method was also highly correlated (r(2) = 0.99) with the first derivative UV method for soluble chitosan.

Expression of chitin deacetylase from Colletotrichum lindemuthianum in Pichia pastoris: purification and characterization

The chitin deacetylase gene from Colletotrichum lindemuthianum UPS9 was isolated and cloned in Pichia pastoris as a tagged protein with six added terminal histidine residues. The expressed enzyme was recovered from the culture supernatant and further characterized. A single-step purification based on specific binding of the histidine residues was achieved. The purified enzyme has a molecular mass of 25 kDa and is not glycosylated as determined by mass spectrometry. The activity of the recombinant chitin deacetylase on chitinous substrates was investigated. With chitotetraose as substrate, the optimum temperature and pH for enzyme activity are 60 degrees C and 8.0, respectively. The specific activity of the pure protein is 72 U/mg. One unit of enzyme activity is defined as the amount of enzyme that produces 1 micromol of acetate per minute under the assay conditions employed. The enzyme activity is enhanced in the presence of Co2+ ions. A possible use of the recombinant chitin deacetylase for large-scale biocatalytic conversion of chitin to chitosan is discussed.

Kinetic growth parameters of different amylolytic and non-amylolytic Lactobacillus strains under various salt and pH conditions

Four Lactobacillus species were studied for their ability to grow at high NaCl concentrations and different initial pH values. Lactobacillus plantarum 541 and A6 could ferment glucose and produce lactic acid in the presence of 8% salt in the medium. For strain 541, the specific rate of lactate production (q(lac)) and the yield of lactic acid relative to substrate (Y(p/s)) remained constant, whereas the yield of biomass relative to substrate (Y(x/s)) decreased up to 6% salt. In contrast, for strain A6, Y(p/s) decreased up to 6% salt whereas Y(x/s) did not vary markedly. Combined effects of salt and pH studied through a factorial design did not show significant interaction between salt and pH. The pH was the dominant factor in glucose fermentation for both the strains. Considering overall performance, 4% salt and pH between 6.0 and 6.6 can be taken as appropriate conditions, for the use of both strains as starters in processes where higher salt concentrations are required.

Transdermal Delivery Controlled by a Chitosan Membrane

The release of a drug from a transdermal delivery system with a rate controlling chitosan membrane was analyzed in vitro and in vivo. Lidocaine hydrochloride, a local anesthetic, was used as the model drug. The in vitro permeability of various chitosan membranes for the drug was investigated using a Franz diffusion cell. Drug release was slower through chitosan membranes with a higher degree of deacetylation (% DD) and with a larger thickness. A transdermal chitosan patch was developed using a chitosan membrane for rate control and a chitosan hydrogel as a drug reservoir. The most prolonged release in vitro was obtained with a 95% DD chitosan rate controlling membrane. The transport mechanism was found to be non-Fickian. The functionality of this transdermal patch was studied on the forearm of human volunteers by assessing the anesthetic effect. Patches with 70% and 95% DD membranes delayed the anesthetic effect, increasing the delay with increasing % DD. It was concluded that a combination of chitosan membrane and chitosan hydrogel is a good transparent system for controlled drug delivery and that the release kinetics in vitro at least for lidocaine have a predictive value for its anesthetic effect in vivo. The demonstration of a direct relationship between in vitro drug membrane permeability and its physiological effect might be considered as quite unique.

Genetically modified soybeans: false-positive detection in fermented natural soybean (tempe)

Tempe was prepared using mixtures of natural soybean and genetically modified Roundup Ready (RUR) soybean fermented with natural Rhizopus sp. The amount of RUR soybean was quantified using an ELISA plate test. The RUR signal decreased during fermentation. In the control experiments on fermentation of non-RUR soybean, the tempe gave a false-positive RUR signal. The cross-reacting substance was generated only in non-RUR soybean during fermentation by Rhizopus sp., Rhizopus oligosporus, R. oryzae, Mucor rouxii and Aspergillus awamori.

Characterization of decrystallized chitosan and its application in biosorption of textile dyes

Decrystallized chitosan was produced from shrimp shells with a low degree of crystallinity (10%) and a high anionic dye binding capacity. Raw, mixed dye wastewater from a textile factory was efficiently decolorized using decrystallized chitosan that was more efficient than using normal chitosan and activated carbon. Decolorization reached 90% within 10 min and could be carried out from pH 4.5 to 8.1. Decrystallized chitosan can be regenerated by 2 M H2SO4 and was reusable more than 10 times. It is, therefore, an attractive candidate for the removal of dyes from textile wastewater.

Chitosan-alginate multilayer beads for gastric passage and controlled intestinal release of protein

Chitosan-alginate beads loaded with a model protein, bovine serum albumin (BSA) were investigated to explore the temporary protection of protein against acidic and enzymatic degradation during gastric passage. Optimum conditions were established for preparation of homogenous, spherical, and smooth chitosan-alginate beads loaded with BSA. Multilayer beads were prepared by additional treatment with either chitosan or alginate or both. The presence of chitosan in the coagulation bath during bead preparation resulted in increased entrapment of BSA. During incubation in simulated gastric fluid (SGF pH 1.2), the beads showed swelling and started to float but did not show any sign of erosion. Inclusion of pepsin in the gastric fluid did not show a further effect on the properties of the beads. Release studies were done in simulated gastric fluid (SGF pH 1.2) and subsequently in simulated intestinal fluid (SIF pH 7.5) to mimic the physiological gastrointestinal conditions. After transfer to intestinal fluid, the beads were found to erode, burst, and release the protein. Microscopic and macroscopic observations confirmed that the release of protein was brought about by the burst of beads. Chitosan-reinforced calcium-alginate beads showed delay in the release of BSA. The multilayer beads disintegrated very slowly. The enzymes pepsin and pancreatin did not change the characteristics of BSA-loaded chitosan-alginate beads. Single layer chitosan-alginate beads released 80-90% of the model protein within 12h while multilayer beads released only 40-50% in the same period of time. The release from chitosan-alginate beads and multilayer beads in SIF was further delayed without prior incubation in SGF. It is concluded that alginate beads reinforced with chitosan offer an excellent perspective for controlled gastrointestinal passage of protein drugs.

Quantification and characterization of insoluble chitinous materials in viscous chitosan solutions

Insoluble chitinous materials in highly viscous chitosan solutions can be quantified using the viscosity-lowering action of transglucosidase (EC 2.4.1.24). In chitosan, commonly produced by high temperature deacetylation (90 degrees C), between 70-90% of insoluble chitinous materials were recovered by this enzymatic method whereas only 25% recovery was obtained by the nitrous acid method. The insoluble material recovered after enzyme treatment had a higher degree of deacetylation and a lower degree of crystallization than that after nitrous acid treatment. The results are explained by difference in penetration by enzyme and nitrous acid into the insoluble particle.

Shrimp chitin as substrate for fungal chitin deacetylase

The fungal chitin deacetylases (CDA) studied so far are able to perform heterogeneous enzymatic deacetylation on their solid substrate, but only to a limited extent. Kinetic data show that about 5-10% of the N-acetyl glucosamine residues are deacetylated rapidly. Thereafter enzymatic deacetylation is slow. In this study, chitin was exposed to various physical and chemical conditions such as heating, sonicating, grinding, derivatization and interaction with saccharides and presented as a substrate to the CDA of the fungus Absidia coerulea. None of these treatments of the substrate resulted in a more efficient enzymatic deacetylation. Dissolution of chitin in specific solvents followed by fast precipitation by changing the composition of the solvent was not successful either in making microparticles that would be more accessible to the enzyme. However, by treating chitin in this way, a decrystallized chitin with a very small particle size called superfine (SF) chitin could be obtained. This SF chitin, pretreated with 18% formic acid, appeared to be a good substrate for fungal deacetylase. This was confirmed both by enzyme-dependent deacetylation measured by acetate production as well as by isolation and assay for the degree of deacetylation (DD). In this way chitin (10% DD) was deacetylated by the enzyme into chitosan with DD of 90%. The formic acid treatment reduced the molecular weight of the polymeric chain from 2x10(5) in chitin to 1.2 x 10(4) in the chitosan product. It is concluded that nearly complete enzymatic deacetylation has been demonstrated for low-molecular chitin.

Critical factors in chitin production by fermentation of shrimp biowaste

Factors affecting Lactobacillus fermentation of shrimp waste for chitin and protein liquor production were determined. The objective of the fermentation is medium conditioning by Lactobacillus through production of proteases and lowering of the pH. The efficiency was tested by conducting fermentation of biowaste in 1-1 beakers with or without pH adjustment using different acids. Addition of 5% glucose to the biowaste supported the growth of lactic acid bacteria and led to better fermentation. Among four acids tested to control pH at the start and during fermentation, acetic acid and citric acid proved to be the most effective. In biowaste fermented with 6.7% L. plantarum inoculum, 5% glucose, and pH 6.0 adjusted with acetic acid, 75% deproteination and 86% demineralization was achieved. Replacement of acetic acid by citric acid gave 88% deproteination and 90% demineralization. The fermentation carried out in the presence of acetic acid resulted in a protein fraction that smelled good and a clean chitin fraction.

Effects of innervation by ciliary ganglia on developing muscle in vitro

Electrophysiological and pharmacological properties of neuromuscular junctions formed in tissue culture between chick ciliary ganglia and chick skeletal muscle cells have been studied. Functional neuromuscular junctions are formed already within 24 h. No functional acetylcholine (ACh) esterase is present at these end-plates. The neurites conduct action potentials to the neuromuscular junctions, where EPPs are generated. Tetrodotoxin (TTX) blocks this nerve conduction but in the presence of TTX MEPP-like potentials remain whose amplitudes are lowered when the Mg2+/Ca2+ ratio in the medium is raised. It is speculated that these large TTX-resistant potentials are multiquantal. The relatively high resting membrane potential in non-innervated muscle fibers was not changed by innervation. ACh-sensitivity was determined by iontophoretical application of ACh to the myotubes. Non-innervated myotubes exhibited an evenly distributed ACh-sensitivity. Local differences in ACh-sensitivity were always gradual and never exceeded a factor of 3. Innervation did not alter the overall ACh-sensitivity, but on functionally innervated muscle cells loci hypersensitive to ACh were found. Hypersensitivity was located within sharply defined areas. Apparently the parasympathetic neurons of the ciliary ganglion are able to form functional neuromuscular junctions with skeletal muscle cells in tissue culture and to induce the formation of regions of high ACh-sensitivity.