Search

This study presents the synthesis of novel silver/poly(vinyl alcohol)/chitosan/graphene (Ag/PVA/CHI/Gr) nanocomposite hydrogels by in situ electrochemical reduction of silver ions in the hydrogel matrix and their thorough characterization by UV-visible and Raman spectroscopies, field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and silver release measurements. The influence of chitosan content on the incorporation and stabilization of silver nanoparticles (AgNPs) was investigated, and we found that hydrogels with higher chitosan content contain higher amounts of AgNPs. In addition, the cytotoxicity and antibacterial activity of Ag/PVA/CHI/Gr nanocomposite hydrogels were evaluated. Based on in vitro investigations, the obtained materials exhibit diffusion-controlled release profiles over 28 days, strong antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains, and no cytotoxicity toward human and mice fibroblast cell lines.

This study presents the synthesis of novel silver/poly(vinyl alcohol)/chitosan/graphene (Ag/PVA/CHI/Gr) nanocomposite hydrogels by in situ electrochemical reduction of silver ions in the hydrogel matrix and their thorough characterization by UV-visible and Raman spectroscopies, field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and silver release measurements. The influence of chitosan content on the incorporation and stabilization of silver nanoparticles (AgNPs) was investigated, and we found that hydrogels with higher chitosan content contain higher amounts of AgNPs. In addition, the cytotoxicity and antibacterial activity of Ag/PVA/CHI/Gr nanocomposite hydrogels were evaluated. Based on in vitro investigations, the obtained materials exhibit diffusion-controlled release profiles over 28 days, strong antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains, and no cytotoxicity toward human and mice fibroblast cell lines.

This study presents the synthesis of novel silver/poly(vinyl alcohol)/chitosan/graphene (Ag/PVA/CHI/Gr) nanocomposite hydrogels by in situ electrochemical reduction of silver ions in the hydrogel matrix and their thorough characterization by UV-visible and Raman spectroscopies, field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and silver release measurements. The influence of chitosan content on the incorporation and stabilization of silver nanoparticles (AgNPs) was investigated, and we found that hydrogels with higher chitosan content contain higher amounts of AgNPs. In addition, the cytotoxicity and antibacterial activity of Ag/PVA/CHI/Gr nanocomposite hydrogels were evaluated. Based on in vitro investigations, the obtained materials exhibit diffusion-controlled release profiles over 28 days, strong antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains, and no cytotoxicity toward human and mice fibroblast cell lines.

Silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/graphene nanocomposites in different forms (colloid dispersion, thin films and hydrogel discs) were synthesized by electrochemical reduction of Ag+ ions at constant current density. CV, Raman, XRD, FT-IR, and XPS analyses were used to characterize the interactions between silver nanoparticles, PVA molecules, and graphene. Ag/PVA/Gr nanocomposites had better mechanical and thermal properties and higher antibacterial activity against Staphylococcus aureus and Escherichia coli than Ag/PVA nanocomposites. Slow silver release, as well as a high remaining silver content (76%) after 28 days in simulated body fluid confirmed that both Ag/PVA and Ag/PVA/Gr nanocomposites are capable of maintaining sterility over time.

Silver/poly(vinyl alcohol), Ag/PVA, and silver/poly(vinyl alcohol)/graphene, Ag/PVA/Gr, composite hydrogel discs were produced by freezing/thawing, followed by electrochemical reduction of Ag+ ions inside respective matrices, at constant voltage in specially designed electrochemical cell. Raman, FT-IR and FE-SEM characterized interactions between PVA, graphene and silver nanoparticles. Ag/PVA and Ag/PVA/Gr discs classified as non-cytotoxic towards peripheral blood mononuclear cells (PBMC) according to MTT cytotoxicity test, while exhibiting antibacterial activity against Staphylococcus aureus and Escherichia coli. The slow silver release and high remaining silver content of similar to 67-68 wt % after 28 day immersion in simulated body fluid confirmed that both composites can preserve their sterility overtime.

Silver/poly(vinyl alcohol), Ag/PVA, and silver/poly(vinyl alcohol)/graphene, Ag/PVA/Gr, composite hydrogel discs were produced by freezing/thawing, followed by electrochemical reduction of Ag+ ions inside respective matrices, at constant voltage in specially designed electrochemical cell. Raman, FT-IR and FE-SEM characterized interactions between PVA, graphene and silver nanoparticles. Ag/PVA and Ag/PVA/Gr discs classified as non-cytotoxic towards peripheral blood mononuclear cells (PBMC) according to MTT cytotoxicity test, while exhibiting antibacterial activity against Staphylococcus aureus and Escherichia coli. The slow silver release and high remaining silver content of similar to 67-68 wt % after 28 day immersion in simulated body fluid confirmed that both composites can preserve their sterility overtime.

Silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/graphene nanocomposites in different forms (colloid dispersion, thin films and hydrogel discs) were synthesized by electrochemical reduction of Ag+ ions at constant current density. CV, Raman, XRD, FT-IR, and XPS analyses were used to characterize the interactions between silver nanoparticles, PVA molecules, and graphene. Ag/PVA/Gr nanocomposites had better mechanical and thermal properties and higher antibacterial activity against Staphylococcus aureus and Escherichia coli than Ag/PVA nanocomposites. Slow silver release, as well as a high remaining silver content (76%) after 28 days in simulated body fluid confirmed that both Ag/PVA and Ag/PVA/Gr nanocomposites are capable of maintaining sterility over time.

Silver/poly(vinyl alcohol) and silver/poly(vinyl alcohol)/graphene nanocomposites in different forms (colloid dispersion, thin films and hydrogel discs) were synthesized by electrochemical reduction of Ag+ ions at constant current density. CV, Raman, XRD, FT-IR, and XPS analyses were used to characterize the interactions between silver nanoparticles, PVA molecules, and graphene. Ag/PVA/Gr nanocomposites had better mechanical and thermal properties and higher antibacterial activity against Staphylococcus aureus and Escherichia coli than Ag/PVA nanocomposites. Slow silver release, as well as a high remaining silver content (76%) after 28 days in simulated body fluid confirmed that both Ag/PVA and Ag/PVA/Gr nanocomposites are capable of maintaining sterility over time.

The main objectives of the paper were to study the effects of nutrient supplementation of cows' whey on the growth and viability of the probiotic microorganism Lactobacillus johnsonii NRRL B-2178. Because of the short lifespan of probiotics, this study was aimed at the evaluation of the contribution of nutrients in the improvement of growth and viability of the microorganism for the purpose of its further application in the formulation of whey-based beverages. A maximal cell growth of 8.70 log(10) cfu mL(-1) and viability of less than 5 days were achieved during the fermentation of whey supplemented with yeast extract (3.0%) and inulin (1.0%), including the synergistic effect of temperature 39 degrees C. Elimination of inulin from the fermentation process reduced the viable cell count by 0.2 log(10) cfu mL(-1), but the addition of 1.0% inulin after fermentation extended the viability of Lb. johnsonii NRRL B-2178 by 10 days.

In this work, we present a comprehensive approach to evaluation of alginate microbeads with included silver nanoparticles (AgNPs) at the concentration range of 0.3-5 mM for potential biomedical use by combining cytotoxicity, antibacterial activity, and silver release studies. The microbeads were investigated regarding drying and rehydration showing retention of similar to 80-85% of the initial nanoparticles as determined by UV-vis and SEM analyses. Both wet and dry microbeads were shown to release AgNPs and/or ions inducing similar growth delays of Staphylococcus aureus and Escherichia coli at the total released silver concentrations of similar to 10 mu g/ml. On the other hand, these concentrations were highly toxic for bovine chondrocytes in conventional monolayer cultures while nontoxic when cultured in alginate microbeads under biomimetic conditions in 3D perfusion bioreactors. The applied approach outlined directions for further optimization studies demonstrating Ag/alginate microbeads as potentially attractive components of soft tissue implants as well as antimicrobial wound dressings.

In this work, we present a comprehensive approach to evaluation of alginate microbeads with included silver nanoparticles (AgNPs) at the concentration range of 0.3-5 mM for potential biomedical use by combining cytotoxicity, antibacterial activity, and silver release studies. The microbeads were investigated regarding drying and rehydration showing retention of similar to 80-85% of the initial nanoparticles as determined by UV-vis and SEM analyses. Both wet and dry microbeads were shown to release AgNPs and/or ions inducing similar growth delays of Staphylococcus aureus and Escherichia coli at the total released silver concentrations of similar to 10 mu g/ml. On the other hand, these concentrations were highly toxic for bovine chondrocytes in conventional monolayer cultures while nontoxic when cultured in alginate microbeads under biomimetic conditions in 3D perfusion bioreactors. The applied approach outlined directions for further optimization studies demonstrating Ag/alginate microbeads as potentially attractive components of soft tissue implants as well as antimicrobial wound dressings.

The main objectives of the paper were to study the effects of nutrient supplementation of cows' whey on the growth and viability of the probiotic microorganism Lactobacillus johnsonii NRRL B-2178. Because of the short lifespan of probiotics, this study was aimed at the evaluation of the contribution of nutrients in the improvement of growth and viability of the microorganism for the purpose of its further application in the formulation of whey-based beverages. A maximal cell growth of 8.70 log(10) cfu mL(-1) and viability of less than 5 days were achieved during the fermentation of whey supplemented with yeast extract (3.0%) and inulin (1.0%), including the synergistic effect of temperature 39 degrees C. Elimination of inulin from the fermentation process reduced the viable cell count by 0.2 log(10) cfu mL(-1), but the addition of 1.0% inulin after fermentation extended the viability of Lb. johnsonii NRRL B-2178 by 10 days.

In this work, we present a comprehensive approach to evaluation of alginate microbeads with included silver nanoparticles (AgNPs) at the concentration range of 0.3-5 mM for potential biomedical use by combining cytotoxicity, antibacterial activity, and silver release studies. The microbeads were investigated regarding drying and rehydration showing retention of similar to 80-85% of the initial nanoparticles as determined by UV-vis and SEM analyses. Both wet and dry microbeads were shown to release AgNPs and/or ions inducing similar growth delays of Staphylococcus aureus and Escherichia coli at the total released silver concentrations of similar to 10 mu g/ml. On the other hand, these concentrations were highly toxic for bovine chondrocytes in conventional monolayer cultures while nontoxic when cultured in alginate microbeads under biomimetic conditions in 3D perfusion bioreactors. The applied approach outlined directions for further optimization studies demonstrating Ag/alginate microbeads as potentially attractive components of soft tissue implants as well as antimicrobial wound dressings.

The main objectives of the paper were to study the effects of nutrient supplementation of cows' whey on the growth and viability of the probiotic microorganism Lactobacillus johnsonii NRRL B-2178. Because of the short lifespan of probiotics, this study was aimed at the evaluation of the contribution of nutrients in the improvement of growth and viability of the microorganism for the purpose of its further application in the formulation of whey-based beverages. A maximal cell growth of 8.70 log(10) cfu mL(-1) and viability of less than 5 days were achieved during the fermentation of whey supplemented with yeast extract (3.0%) and inulin (1.0%), including the synergistic effect of temperature 39 degrees C. Elimination of inulin from the fermentation process reduced the viable cell count by 0.2 log(10) cfu mL(-1), but the addition of 1.0% inulin after fermentation extended the viability of Lb. johnsonii NRRL B-2178 by 10 days.

Expansion of lactic acid applications, predominantly for the preparation of biodegradable polymers increased the research interest for new, economically favourable production processes. Liquid stillage from bioethanol production can be an inexpensive, valuable source of nutrients for growth of lactic acid bacteria. Utilisation of residual biomass with spent fermentation media as a functional animal feed can greatly influence the process value and its ecological aspect. In this paper, the kinetics of lactic acid and biomass production on liquid stillage by Lactobacillus rhamnosus ATCC 7469 was studied. In addition, the impact of temperature, inoculum concentration, shaking and pH control by addition of CaCO3 was evaluated. Maximal lactic acid yield of 73.4%, as well as high biomass production (3 x 10(8) CFU ml(-1)) were achieved under selected conditions (41 degrees C, 5% (v/v) of inoculum, 1% (w/v) of CaCO3, initial pH of 6.5 and shaking rate of 90 rpm). These results were achieved without supplementation of the stillage with nitrogen or mineral sources.

Expansion of lactic acid applications, predominantly for the preparation of biodegradable polymers increased the research interest for new, economically favourable production processes. Liquid stillage from bioethanol production can be an inexpensive, valuable source of nutrients for growth of lactic acid bacteria. Utilisation of residual biomass with spent fermentation media as a functional animal feed can greatly influence the process value and its ecological aspect. In this paper, the kinetics of lactic acid and biomass production on liquid stillage by Lactobacillus rhamnosus ATCC 7469 was studied. In addition, the impact of temperature, inoculum concentration, shaking and pH control by addition of CaCO3 was evaluated. Maximal lactic acid yield of 73.4%, as well as high biomass production (3 x 10(8) CFU ml(-1)) were achieved under selected conditions (41 degrees C, 5% (v/v) of inoculum, 1% (w/v) of CaCO3, initial pH of 6.5 and shaking rate of 90 rpm). These results were achieved without supplementation of the stillage with nitrogen or mineral sources.

Vegetables are rich sources of the biologically active compounds which have beneficial effects in prevention of some diseases and certain types of cancer. From the point of view of protection and health, the objective of this paper was to optimize food content in order to obtain a functional food. In order to improve the nutritive and protective properties of the product, the beetroot and carrot juices enriched with brewer's yeast autolysate were subjected to lactic-acid fermentation with Lactobacillus acidophilus NCDO1748. Chemical compositions of produced fermented bioproducts showed that fermented carrot juice with brewer's yeast autolysate had higher contents of some minerals (Ca, P, Fe) and P-carotene than had beetroot juice with brewer's yeast autolysate. Higher mineral content in the carrot juice better affected production of lactic acid in that sample. Fermented beetroot juice with brewer's yeast autolysate had higher contents of betanin and vitamin C, which were in accordance with the contents of these components in raw beetroot that did not significantly vary during the processing of the material (pasteurization, fermentation). Thus the fermented bioproduct 3, which is a mixture of beetroot and carrot juices with brewer's yeast autolysate, represents the product with optimum proportions of pigments, vitamins and minerals.

Vegetables are rich sources of the biologically active compounds which have beneficial effects in prevention of some diseases and certain types of cancer. From the point of view of protection and health, the objective of this paper was to optimize food content in order to obtain a functional food. In order to improve the nutritive and protective properties of the product, the beetroot and carrot juices enriched with brewer's yeast autolysate were subjected to lactic-acid fermentation with Lactobacillus acidophilus NCDO1748. Chemical compositions of produced fermented bioproducts showed that fermented carrot juice with brewer's yeast autolysate had higher contents of some minerals (Ca, P, Fe) and P-carotene than had beetroot juice with brewer's yeast autolysate. Higher mineral content in the carrot juice better affected production of lactic acid in that sample. Fermented beetroot juice with brewer's yeast autolysate had higher contents of betanin and vitamin C, which were in accordance with the contents of these components in raw beetroot that did not significantly vary during the processing of the material (pasteurization, fermentation). Thus the fermented bioproduct 3, which is a mixture of beetroot and carrot juices with brewer's yeast autolysate, represents the product with optimum proportions of pigments, vitamins and minerals.

The two-step enzymatic hydrolysis of corn meal by commercially available a-amylase and glucoamylase and further ethanol fermentation of the obtained hydrolyzates by Saccharomyces cerevisiae yeast was studied. The conditions of starch hydrolysis such as substrate and enzyme concentration and the time required for enzymatic action were optimized taking into account both the effects of hydrolysis and ethanol fermentation. The corn meal hydrolyzates obtained were good substrates for ethanol fermentation by S. cerevisiae. The yield of ethanol of more than 80% (w/w) of the theoretical was achieved with a satisfactory volumetric productivity P (g/l h). No shortage of fermentable sugars was observed during simultaneous hydrolysis and fermentation. In this process, the savings in energy by carrying out the saccharification step at lower temperature (32 degrees C) could be realized, as well as a reduction of the process time for 4 h.

The two-step enzymatic hydrolysis of corn meal by commercially available a-amylase and glucoamylase and further ethanol fermentation of the obtained hydrolyzates by Saccharomyces cerevisiae yeast was studied. The conditions of starch hydrolysis such as substrate and enzyme concentration and the time required for enzymatic action were optimized taking into account both the effects of hydrolysis and ethanol fermentation. The corn meal hydrolyzates obtained were good substrates for ethanol fermentation by S. cerevisiae. The yield of ethanol of more than 80% (w/w) of the theoretical was achieved with a satisfactory volumetric productivity P (g/l h). No shortage of fermentable sugars was observed during simultaneous hydrolysis and fermentation. In this process, the savings in energy by carrying out the saccharification step at lower temperature (32 degrees C) could be realized, as well as a reduction of the process time for 4 h.