Effect of chitosan addition on the properties of films prepared with corn and cassava starches.

Starch and chitosan are biodegradable polymers from renewable sources that can be used to overcome the serious environmental problem caused by improper disposal of synthetic plastic materials, non-biodegradable, derived from petroleum sources. The starch-chitosan based films manufactured allow improving the better characteristics of each one, adding their good characteristics and compensating for some limitations. In this work, it was studied: two sources of starch (corn and cassava), two different modes of chitosan addition (chitosan blended in the starch filmogenic solution and chitosan as coating), and the effect of glutaraldehyde as crosslinking agent. All films were prepared by casting using glycerol as a plasticizer and were characterized by their physicochemical (water vapor permeability, water contact angle, and FTIR), mechanical, and antimicrobial properties. The properties analyzed were influenced by all variables tested. Moreover, the principal component analysis was also conducted in order to relate and describe the variables analyzed. The antimicrobial activity of the corn starch-based films containing chitosan was confirmed, and these films have potential for development of active packaging.

Gelatin-based films containing clinoptilolite-Ag for application as wound dressing.

Dressings used in burns and chronic wounds treatment must present antimicrobial characteristics. Silver-based compounds are used for a long time as antiseptics, but they present problems related to the release of silver. In order to control the release, Ag+ ions may be immobilized in supports that must be dispersed in the film used as wound dressing. In this work gelatin-based films using glycerol as plasticizer and incorporated with different concentrations of clinoptilolite zeolite impregnated with silver ions were prepared and characterized, and the potential antimicrobial activity was investigated. For this purpose, films were produced by casting and evaluated in relation to their mechanical, chemical, thermal, morphological and antimicrobial properties, in addition the amount of silver present in the films was quantified and the kinetics of Ag+ release in vitro was studied. The antimicrobial analysis was done qualitatively, using Escherichia coli and Staphylococcus aureus bacteria and the microorganisms commonly present on human skin collected with a swab, and quantitatively, using Escherichia coli and Staphylococcus aureus. Characterization tests demonstrated that the glycerol concentration of 25% and the zeolite concentration of 0.5% resulted in films with more suitable properties for wound dressing applications and the silver release test showed that the release of the active compound occurs slowly, as expected. All gelatin/clinoptilolite-Ag films showed antibacterial activity against Staphylococcus aureus and human skin bacteria, not presenting expressive differences on the size of the formed halo. Moreover, by the quantitative antimicrobial analisys, it was observed that as the glycerol concentration increases, the antimicrobial action was faster and at the end of the experiment, there were no S. aureus in the solutions where the films were immersed and for the assay with E. coli, the bactericidal activity is slower and probably is needed a higher concentration of silver ions in the sample to completely inhibit the bacteria. However, the bactericidal activity of the gelatin/clinoptilolite-Ag films was satisfactory due its effectiveness in reducing bacterial growth of E. coli and S. aureus. Based on these results the prepared gelatin/clinoptilolite-Ag films could serve as a promising wound dressing with great antibacterial properties, thus possibly helping also the wound healing.

Poly(3-Hydroxybutyrate) Production in Repeated fed-Batch with Cell Recycle Using a Medium with low Carbon Source Concentration.

Among approaches applied to obtain high productivity and low production costs in bioprocesses are high cell density and the use of low cost substrates. Usually low cost substrates, as waste/agroindustrial residues, have low carbon concentration, which leads to a difficulty in operating bioprocesses. Real time control of process for intracellular products is also difficult. The present study proposes a strategy of repeated fed-batch with cell recycle to attain high cell density of Cupriavidus necator and high poly(3-hydroxybutyrate) (P(3HB)) productivity, using a substrate with low carbon source concentration (90 g l(-1)). Also, the use of the oxygen uptake rate data was pointed out as an on line solution for process control, once P(3HB) is an intracellular product. The results showed that total biomass (X), residual biomass (Xr) and P(3HB) values at the end of the culture were 61.6 g l(-1), 19.3 g l(-1) and 42.4 g l(-1) respectively, equivalent to 68.8 % of P(3HB) in the cells, and P(3HB) productivity of 1.0 g l(-1) h(-1). Therefore, the strategy proposed was efficient to achieve high productivity and high polymer content from a medium with low carbon source concentration.

Separation of phycocyanin from Spirulina platensis using ion exchange chromatography.

This paper presents the evaluation of some important parameters for the purification of phycocyanin using ion exchange chromatography. The influences of pH and temperature on the equilibrium partition coefficient were investigated to establish the best conditions for phycocyanin adsorption. The equilibrium isotherm for the phycocyanin-resin system was also determined. The separation of phycocyanin using the Q-Sepharose ion exchange resin was evaluated in terms of the pH and elution volume that improved the increase in purity and recovery. The highest partition coefficients were obtained in the pH range from 7.5 to 8.0 at 25 degrees C. Under these conditions the equilibrium isotherm for phycocyanin adsorption was well described by the Langmuir model, attaining a Q (m) of 22.7 mg/mL and K (d) of 3.1 x 10(-2) mg/mL. The best conditions for phycocyanin purification using the ion exchange column were at pH 7.5 with an elution volume of 36 mL, obtaining 77.3% recovery and a 3.4-fold increase in purity.