Application of Films Based on Chitosan and Xanthan Gum in Refrigerated Fish Conservation

Abstract This research aims to determine the efficiency of chitosan and xanthan gum films in conservation of croaker fillets kept in refrigeration for 9 days. Proximal composition, loss of mass, color, pH, TVB-N (Total Volatile Bases) and microbiological profile were assessed. The films were prepared with chitosan and xanthan gum in varying mass proportions 100:0, m:m (C100XG0); 60:40, m:m (C60XG40); 50:50, m:m (C50XG50). They presented the respective values for moisture content, water solubility, thickness and water vapor permeability: 24.59%, 19.50%, 0.086 mm and 11.45gm-1.s-1.Pa-1for C100XG0; 24.58%; 20.27%, 0.091 mm and 10.41 gm-1.s-1.Pa-1for C60XG40; 22.11%, 22.06%, 0.089 mm and 10.68 gm-1.s-1.Pa-1 forC50XG50.The films were made in small bags format capable to hold about 20 g of fish fillets. A control sample was prepared in parallel, using polyethylene bags under the same storage conditions. The results showed that the chitosan films combined with xanthan gum had excellent antimicrobial properties, capable of preserving the quality of chilled fish fillets during the studied period, since it inhibited the growth of Staphylococcus coagulase-positive, Salmonella spp and coliforms at 45 ° C. Mass loss of the croaker fillets was not significantly affected by xanthan gum addition to the films. On the other hand, xanthan gum addition affected pH and color parameters of the corvina fillets. It was also verified that the combination of these two polymers promoted the reduction of N-BVT, being the C50XG50 film that presented the best response.

Exopolysaccharide production from Bacillus velezensis KY471306 using statistical experimental design

Abstract Exopolysaccharide (EPS) biopolymers produced by microorganisms play a crucial role in the environment such as health and bio-nanotechnology sectors, gelling agents in food and cosmetic industries in addition to bio-flocculants in the environmental sector as they are degradable, nontoxic. This study focuses on the improvement of EPS production through manipulation of different culture and environmental conditions using response surface methodology (RSM). Plackett-Burman design indicated that; molasses, yeast extract and incubation temperature are the most effective parameters. Box-Behnken RSM indicated that; the optimum concentration for each parameter was 12% (w/v) for molasses, 6 g/L yeast extract and 30 °C for incubation temperature. The most potent bacterial isolate was identified as Bacillus velezensis KY498625. After production, EPS was extracted, purified using DEAE-cellulose, identified using Fourier transform infrared (FTIR), gel permeation chromatography (GPC) and gas chromatography-mass spectroscopy (GC-MS). The result indicated that; it has molecular weight 1.14 × 105 D consisting of glucose, mannose and galactose.

Exopolysaccharide dispelled by calcium hydroxide with volatile vehicles related to bactericidal effect for root canal medication

ABSTRACT Objective: Enterococcus faecalis is the dominant microbial species responsible for persistent apical periodontitis with ability to deeply penetrate into the dentin. Exopolysaccharides (EPS) contribute to the pathogenicity and antibiotic resistance of E. faecalis. Our aim was to investigate the antimicrobial activity of calcium hydroxide (CH), camphorated parachlorophenol (CMCP), and chlorhexidine (CHX) against E. faecalis in dentinal tubules. Material and Methods: Decoronated single-canal human teeth and semicylindrical dentin blocks were incubated with E. faecalis for 3 weeks. Samples were randomly assigned to six medication groups for 1 week (n=10 per group): CH + 40% glycerin-water solution (1:1, wt/vol); CMCP; 2% CHX; CH + CMCP (1:1, wt/vol); CH + CMCP (2:3, wt/vol); and saline. Bacterial samples were collected and assayed for colony-forming units. After dentin blocks were split longitudinally, confocal laser scanning microscopy was used to assess the proportion of viable bacteria and EPS production in dentin. Results: CMCP exhibited the best antimicrobial activity, while CH was the least sensitive against E. faecalis (p<0.05). CHX showed similar antimicrobial properties to CH + CMCP (1:1, wt/vol) (p>0.05). CH combined with CMCP inhibited EPS synthesis by E. faecalis, which sensitized biofilms to antibacterial substances. Moreover, increasing concentrations of CMCP decreased EPS matrix formation, which effectively sensitized biofilms to disinfection agents. Conclusion: The EPS matrix dispelled by CH paste with CMCP may be related to its bactericidal effect; the visualization and analysis of EPS formation and microbial colonization in dentin may be a useful approach to verify medicaments for antimicrobial therapy.

Structure of xanthan gum and cell ultrastructure at different times of alkali stress

Abstract The effect of alkali stress on the yield, viscosity, gum structure, and cell ultrastructure of xanthan gum was evaluated at the end of fermentation process of xanthan production by Xanthomonas campestris pv. manihotis 280-95. Although greater xanthan production was observed after a 24 h-alkali stress process, a lower viscosity was observed when compared to the alkali stress-free gum, regardless of the alkali stress time. However, this outcome is not conclusive as further studies on gum purification are required to remove excess sodium, verify the efficiency loss and the consequent increase in the polymer viscosity. Alkali stress altered the structure of xanthan gum from a polygon-like shape to a star-like form. At the end of the fermentation, early structural changes in the bacterium were observed. After alkali stress, marked structural differences were observed in the cells. A more vacuolated cytoplasm and discontinuities in the membrane cells evidenced the cell lysis. Xanthan was observed in the form of concentric circles instead of agglomerates as observed prior to the alkali stress.

Composition of Extracellular Polymeric Substances (EPS) produced by Flavobacterium columnare isolated from tropical fish in Brazil

Thirty nine isolates of Flavobacterium columnare from Brazilian fish farms had their carbohydrate composition of EPS evaluated by high efficiency liquid chromatography, using the phenol-sulfuric acid method of EPS. The occurrence of capsules on F. columnare cells was not directly related to biofilm formation, and the predominant monosaccharide is glucose.

Levan as a new additive for colon-specific films: a new approach in the use of exopolysaccharides in time-dependent free films [Aminoalkyl Methacrylate Copolymer RS]

Time-dependent films, augmented with prebiotics, offer potential strategy for colon-specific controlled drug release. In this study, we produced films containing levan [L] and Aminoalkyl Methacrylate Copolymer RS [ER]. Free films of ER combined with levan were produced by the casting process and characterized by the mobility of the polymeric matrix, hydration, differential scanning calorimetry [DSC] and thermogravimetry [TGA]. The results of this study suggest that the exopolysaccharide levan can be used in combination with ER for colon specific materials. No evidence of incompatibilities between the levan and the synthetic polymer were detected, and levan improved the mobility of the polymeric matrix and the hydrophilicity of the system. Levan may have positively altered the density of the polymeric matrix, as visualized by thermal characterization. The endothermic decomposition peak was shifted with increasing amounts of levan. This new barrier polymer utilized a combination of time-dependent enzymatic mechanisms and can be considered promising for use in the coating of solid oral drugs for specific release

A half-century of streptococcal research: then & now.

Research on Group A streptococci (GAS) before 1950 paved the way for successful clinical trials to prevent acute rheumatic fever (ARF) by treating the prior streptococcal infection with penicillin. Prevention of ARF has led to almost complete disappearance of rheumatic heart disease in the industrialized world, but has yet to be accomplished in developing countries, where most of the world's populations reside. Twenty years of research beginning in 1918 by Lancefield and others delineated the modern classification of haemolytic streptococci and led to the recognition that only Group A is responsible for the pharyngitis that causes ARF. M-protein, identified as a major virulence factor, is a powerful inhibitor of phagocytosis, and antibodies to it promote type-specific phagocytosis and therefore type-specific immunity. Other virulent properties of GAS include a bulky capsule, as well as extracellular toxins such as streptolysins S and O and streptococcal proteinase. McCarty and others pursued the cell biology of GAS and identified the cellular localization of various antigenic components. The discovery of purified M-protein as a helical coiled-coiled fibrillar protein has sparked development of M-protein vaccine. US, UK, and Trinidad scientists described differences between streptococcal infections of the throat and skin and noted particularly that many of the GAS M-types that cause impetigo are less likely to cause pharyngitis. GAS impetigo may cause acute glomerulonephritis, but such infections do not result in ARF. The changing manifestations of disease over time and the evolution of microbes are common themes in medicine today. These themes are relevant to GAS pharyngitis and ARF, especially the decline in the incidence of severe ARF and the decrease in severity of GAS pharyngitis. Research on GAS bacteriophages led to the discovery of a relationship between lysogenic GAS and production of erythrogenic toxin and has broadened approaches to the molecular epidemiology of GAS virulence. The 21st century begins with determination of the complete genome sequence of M-1, M-18, and M-3 strains of GAS. These studies provide evidence for phage-encoded toxins, high-virulence phenotypes, and clone emergence. This research will reveal genetic processes at the molecular level that control the emergence and decline of streptococcal diseases in different places and times and the shifting patterns in clinical manifestations.

Spectrophotometric and spectrofluorometric studies on interaction of cationic dyes with bacterial capsular polysaccharide.

Interaction of Klebsiella K14 capsular polysaccharide with cationic dyes pinacyanol chloride, acridine orange and phenosafranin has been studied by spectrophotometric and spectrofluorometric techniques. The polymer containing both glucuronic acid and pyruvic acid in its repeating unit behaved as a unique polyelectrolyte. It induced blue shift of the absorption band of pinacyanol chloride indicating strong metachromasy. Stoichiometry of the polyanion and the dye cations in the polymer-dye compound (1:2) indicated that both glucuronic acid and pyruvic acid acted as potential anionic sites for interaction with the cationic dye molecules. The stoichiometry of anionic site (of polyanion): cationic site (of dye) in the polymer dye compound was calculated as 1:1. Interaction of the polymer with acridine orange and phenosafranin dyes studied by fluorescence measurements demonstrated Stern-Volmer type of quenching. Equivalent weight of the polymer was determined by spectrophotometric and spectrofluorometric titrations. From the present studies chromotropic property of the polymer was established.

Studies on induction of metachromasy in cationic dye pinacyanol chloride by Klebsiella K7 capsular polysaccharide.

The acidic capsular polysaccharide isolated from Klebsiella K7 induced metachromasy in the cationic dye pinacyanol chloride indicating its chromotropic character. Interaction of the biopolymer with the cationic dye was studied by visible absorption spectrophotometry, and thermodynamic parameters of the interaction evaluated. The polymer induced a metachromatic blue shift in the spectrum from 600 nm to 495 nm. The spectral changes were studied during interaction of the dye with the polymer at different polymer/dye molar ratios (P/D = 0 approximately 50). Effects of co-solvents on the stability of the dye-polymer compound were studied. A complete reversal of metachromasy was observed upon addition of different alcohols and urea solution. Thermodynamic parameters obtained from the spectral data indicated chromotropic character of the polymer in interacting with the cationic dye molecules in solution.

Absorption and fluorescence studies on interaction between cationic dyes and Klebsiella K7 capsular polysaccharide.

Interaction of cationic dyes, pinacyanol chloride, acridine orange and phenosafranin, with Klebsiella K7 capsular polysaccharide has been investigated by spectrophotometric and spectrofluorometric measurements. The acidic polysaccharide induce a metachromatic blue shift of the absorption band of pinacyanol chloride from 600 nm to 495 nm, indicating strong metachromasy. Stoichiometry of polyanion and dye cation (1:1.5) in the polymer-dye compound formed by the interaction between pinacyanol chloride dye and K7 polymer indicate that both glucuronic acid and pyruvic acid act as the potential anionic sites for interaction. Both spectrophotometric titration of pinacyanol chloride and spectrofluorometric titration of acridine orange and phenosafranin dyes by the polymer gave quite comparable equivalent weights for the polymer. Dye-polymer interaction studies indicated induction of metachromasy in the cationic dye by the anionic biopolymer, establishing its chromotropic character.

Chromotropic character of bacterial acidic polysaccharides: Part III--Interaction of cationic dye pinacyanol chloride with Klebsiella K15 capsular polysaccharide.

Interaction of cationic dye pinacyanol chloride with the acidic capsular polysaccharide isolated from Klebsiella serotype K15 has been investigated by spectral measurements. Klebsiella K15 polysaccharide consists of hexasaccharide repeating units containing one residue each of glucuronic acid and glucose, and four residues of galactose. Glucuronic acid acts as the potential anionic site and the biopolymer interacts with the dye cations. It induces metachromasy in the dye and a blue shift of about 100 nm is observed in the visible absorption spectrum of the dye. Spectral measurements have been carried out at different polymer/dye molar ratios. Stoichiometry of polymer and dye in the polyanion-dye compound (1:1) indicates that every potential anionic site of the polyanion is associated with the dye cation, and stacking conformation is thus suggested. Effect of different non-aqueous solvents in reversing metachromasy has also been studied. Interaction studies exhibit chromotropic character of the biopolymer.