Development of a cationic bacterial cellulose film loaded with anionic liposomes for prolonged release of oxacillin in wound dressing applications.

Dressings should protect wounds, promote healing, absorb fluids, and maintain moisture. Bacterial cellulose is a biopolymer that stands out in biomaterials due to its high biocompatibility in several applications. In the area of dressings, it is already marketed as an alternative to traditional dressings. However, it lacks any intrinsic activity; among these, the need for antimicrobial activity in infected wounds stands out. We developed a cationic cellulose film by modifying cellulose with 1-(5-carboxypentyl)pyridin-1-ium bromide, enhancing its wettability (contact angle: 26.6°) and water retention capacity (2714.37 %). This modified film effectively retained oxacillin compared to the unmodified control. Liposomal encapsulation further prolonged oxacillin release up to 11 days. Both oxacillin-loaded films and liposomal formulations demonstrated antimicrobial activity against Staphylococcus aureus. Our findings demonstrate the potential of chemically modified cellulose as a platform for controlled anionic antibiotics and/or their formulations delivery in wound care.

Papain Covalent Immobilization in Bacterial Cellulose Films as a Wound Dressing.

Ideally, the dressings used in the clinic have characteristics that help the wound closure process. Among several factors that affect the success of this healing process, there is debridement. It manages the wound bed components and the re-epithelialization process. Still, the property of debridement is not generally associated with dressings. Here, we show a chemically modified bacterial cellulose film conjugated to a proteolytic enzyme, papain, as a dressing with debridement properties. Bacterial cellulose films were reacted with a spacer derived from succinic acid and finally had this enzyme covalently immobilized in its structure by an amide bond. FT-IR and UV-vis showed bands typically of bioconjugated polymer. Enzymatic immobilization was very effective under the conditions applied with high yield (33% w/w), and these remained activated after the coupling reaction. The bacterial cellulose film with the enzyme papain attached to it was also very compatible with fibroblast cells, suggesting that it could be a promising wound dressing material for future research.

Cellulose Hydrogel with Hyaluronic Acid and Silver Nanoparticles: Sustained-Release Formulation with Antibacterial Properties against Pseudomonas aeruginosa.

Pathogenic bacteria resistant to conventional antibiotics represent a global challenge and justify the need for new antimicrobials capable of combating bacterial multidrug resistance. This study describes the development of a topical hydrogel in a formulation composed of cellulose, hyaluronic acid (HA), and silver nanoparticles (AgNPs) against strains of Pseudomonas aeruginosa. AgNPs as an antimicrobial agent were synthesized by a new method based on green chemistry, using arginine as a reducing agent and potassium hydroxide as a carrier. Scanning electron microscopy showed the formation of a composite between cellulose and HA in a three-dimensional network of cellulose fibrils, with thickening of the fibrils and filling of spaces by HA with the presence of pores. Ultraviolet-visible spectroscopy (UV-vis) and particle size distribution for dynamic light scattering (DLS) confirmed the formation of AgNPs with peak absorption at ~430 nm and 57.88 nm. AgNPs dispersion showed a minimum inhibitory concentration (MIC) of 1.5 µg/mL. The time-kill assay showed that after 3 h of exposure to the hydrogel containing AgNPs, there were no viable cells, corresponding to a bactericidal efficacy of 99.999% in the 95% confidence level. We obtained a hydrogel that is easy to apply, with sustained release and bactericidal properties against strains of Pseudomonas aeruginosa at low concentrations of the agent.

Komagataeibacter intermedius V-05: An Acetic Acid Bacterium Isolated from Vinegar Industry, with High Capacity for Bacterial Cellulose Production in Soybean Molasses Medium.

RESEARCH BACKGROUND: Despite the great properties of bacterial cellulose, its manufacture is still limited due to difficulties in large-scale production. These problems are mainly related to low production yields and high overall costs of the conventional culture media normally used. To surpass these problems, it is necessary to identify new cheap and sustainable carbon sources. Thus, this work aims to isolate and select a high cellulose-producing Komagataeibacter strain from vinegar industry, and study its potential for bacterial cellulose synthesis in an industrial soybean co-product, known as soybean molasses, used as fermentation medium. EXPERIMENTAL APPROACH: One isolated strain was able to produce high amount of cellulose in the standard Hestrin-Schramm medium, so we tested its ability to produce this biopolymer in a soybean molasses medium. The characteristics and properties of the produced bacterial cellulose membranes were analyzed by thermogravimetric analysis, X-ray diffraction, infrared spectroscopy, water-holding capacity and rehydration ratio. Genetic analysis of the selected strain served to determine its genus and species. RESULTS AND CONCLUSIONS: An isolated strain that produced the highest amount of cellulose in Hestrin-Schramm medium (3.7 g/L) was genetically identified as Komagataeibacter intermedius V-05. This strain produced 10.0 g/L of cellulose in soybean molasses medium. Membranes from both substrates had similar chemical structure, crystallinity and thermal degradation. Soybean molasses proved to be a suitable alternative medium for biosynthesis of cellulose in comparison with the standard medium. In addition to providing higher production yield, the membranes showed great structural characteristics, similar to those obtained from standard medium. NOVELTY AND SCIENTIFIC CONTRIBUTION: In this research, we have isolated and identified a Komagataeibacter strain which exhibits a high capacity for cellulose production in soybean molasses. The isolation and selection of strains with high capacity for microbial metabolite production is important for decreasing bioprocess costs. Furthermore, as there is a necessity today to find cheaper carbon sources to obtain microbial products at a lower cost, soybean molasses represents an interesting alternative medium to produce bacterial cellulose for its industrial application.

Rhamnolipid production by Pseudomonas aeruginosa grown on membranes of bacterial cellulose supplemented with corn bran water extract.

Surfactants represent a billionaire market of amphiphilic molecules with worldwide applications in almost every branch of modern industry. The most common surfactants, available and currently used, are chemically produced. However, there is an urge to replace these chemical compounds with those obtained by mild and green technologies such as microbial biosurfactants produced by fermentative processes. Rhamnolipids are glycolipid biosurfactants that present highly effective surface-active properties and enormous market potential; nevertheless, their production costs remain not competitive. Here, we present a process of rhamnolipid production by static submerged cultivation using membranes of bacterial cellulose as substrate. The mixture of the rhamnolipid congeners was characterized showing effective surface-active properties and high amount of di-rhamnolipids (95.6%). Through this fermentative technology, 15.8 g/L of rhamnolipid was reach using a very simple and low-cost medium. The present process might decrease biosurfactant production cost, avoid foam formation, and finally make rhamnolipid production more viable.

Synergistic effect of a novel chitosan/silica nanocomposites-based formulation against gray mold of table grapes and its possible mode of action.

Ecofriendly nanostructured materials have been proposed as promising alternative control means to prevent plant diseases. Chitosan nanoparticles (CN), silica nanoparticles (SN) and chitosan-silica nanocomposites (CSN) were synthesized and their morphology and structure was characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), infrared spectra (FT-IR) and Raman spectroscopy. Their antifungal efficiency against Botrytis cinerea, the causal fungus of gray mold disease of table grapes, was tested in vitro and in vivo (under artificial and natural infections). In vitro tests showed that CN, SN and CSN reduced fungal growth by 72, 76 and 100%, respectively at 1% as compared to control. Under natural infection, at the end of cold storage, CSN was the most effective treatment, and reduced the development of gray mold by 59 and 83%, for 'Italia' and 'Benitaka' grapes, respectively as compared to the water control. Results indicate that a synergistic effect of CSN against gray mold was observed. The impact of tested nanocomposites on soluble solids - TSS, titratable acidity - TA, TSS/TA, berry color, mass loss, stem browning and shattered berries was investigated. No negative effect of tested nanomaterials in term of grape quality was observed. For 'Italia' table grape, CN and CSN can preserve bunches from mass loss as compared to control. Also, the effect of CSN on reactive species of oxygen (ROS), ATP content and mitochondrial membrane potential (MMP) of B. cinerea spores was determined to verify its mode of action. The obtained results suggested CSN, as alternative control means, to reduce/substitute the use of fungicides to control gray mold of table grapes while maintaining grape quality.

Production of Cellulose and Profile Metabolites by Fermentation of Glycerol by Gluconacetobacter Xylinus

ABSTRACT Because of the widespread occurrence of cellulose in nature, many organisms use glycerol as a source of carbon and energy, so these organisms have drawn attention to the potential use of glycerol bioconversion. The bacteria Gluconacetobacter xylinus, a strictly aerobic strain that performing incomplete oxidation of various sugars and alcohols to cellulose biosynthesis. For this reason, we modify the Hestrim-Schram medium, associating glycerol, glucose and sucrose varying their concentration. The fermentations were performed statically at a temperature of 28˚C for a period of 10 days. The pH, membrane formation, crystallinity and the production of some metabolites of the 4th, 7th and 10th days was evaluated. The results showed a higher yield of membrane in the medium containing glucose, gly 1 + glu2 on 10 fermentation of 3.5 g %. Through solid-state NMR gave the crystallinity of the membranes, where there was a clear trend toward higher crystallinity membranes with 7 days of fermentation. Metabolic products found in the media by analysis of NMR spectroscopy in liquid were similar, especially for the production of alanine and lactate that were present in all media. The leucine and threonine were present in various media, although in small quantities has been found glutamate.

Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb.

The bacterial cellulose (BC), from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid (HA) is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration. In this study, polymeric composites were produced in presence of hyaluronic acid isolated from chicken comb on different days of fermentation, specifically on the first (BCHA-SABT0) and third day (BCHA-SABT3) of fermentation. The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity. The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid. The results demonstrate that the polymeric composites (BC/HA-SAB) can be produced in situ. The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering.

Combining glucose and sodium acetate improves the growth of Neochloris oleoabundans under mixotrophic conditions.

Mixotrophic cultivation is a potential approach to produce microalgal biomass that can be used as raw materials for renewable biofuels and animal feed, although using a suitable, cost-effective organic carbon source is crucial. Here, we used a Box-Behnken design with three factors, the glucose and sodium acetate concentrations, and the percentage of Bold's basal medium (BBM), to evaluate the effects of different carbon sources on biomass productivity and the protein and lipid contents of Neochloris oleoabundans (UTEX#1185). When grow at optimal levels of these factors, 100 % BBM plus 7.5 g L(-1) each of glucose and sodium acetate, N. oleoabundans yielded 1.75 g L(-1) of dry biomass, with 4.88 ± 0.09 % N, 24.01 ± 0.29-30.5 ± 0.38 % protein, and 34.4 % ± 0.81 lipids. A nuclear magnetic resonance spectrum ((1)H-NMR) of a lipid extract showed that the free fatty acid content was 11.25 %. Thus, combining glucose and sodium acetate during the mixotrophic cultivation of N. oleoabundans can yield greater amounts of biomass, proteins, and lipids for biofuel production.

Bacterial cellulose and hyaluronic acid hybrid membranes: Production and characterization.

In this study, the effect of the addition of hyaluronic acid (HA) on bacterial cellulose (BC) production, under static conditions was evaluated in terms of the properties of the resulting BC hybrid membranes. HA was added to the fermentation process in three distinct time points: first day (BC-T0), third day (BC-T3) and sixth day (BC-T6). Analyses of FT-IR and CP/MAS (13)C NMR confirmed the presence of HA in bacterial cellulose membranes. The crystal structure, crystallinity index (Ic) surface roughness, thermal stability and hybrophobic/hydrophilic character changed. Membranes with higher roughness were produced with HA added on the first and third day of fermentation process. The surface energy of BC/HA membranes was calculated and more hydrophilic membranes were produced by the addition of HA on the third and sixth day, also resulting in more thermally stable materials. The results demonstrate that bacterial cellulose/hyaluronic acid hybrid membranes can be produced in situ and suggest that HA interacts with the sub-elementary bacterial cellulose fibrils, changing the properties of the membranes. The study and understanding of the factors that affect those properties are of utmost importance for the safe and efficient use of BC as biomaterials in numerous applications, specifically in the biological field.

Nanostructural reorganization of bacterial cellulose by ultrasonic treatment.

In this work, bacterial cellulose was subjected to a high-power ultrasonic treatment for different time intervals. The morphological analysis, scanning electron microscopy, and atomic force microscopy revealed that this treatment changed the width and height of the microfibrillar ribbons and roughness of their surface, originating films with new nanostructures. Differential thermal analysis showed a higher thermal stability for ultrasonicated samples with a pyrolysis onset temperature of 208 degrees C for native bacterial cellulose and 250 and 268 degrees C for the modified samples. The small-angle X-ray scattering experiments demonstrated that the treatment with ultrasound increased the thickness of the ribbons, while wide-angle X-ray scattering experiments demonstrated that the average crystallite dimension and the degree of crystallinity also increased. A model is proposed where the thicker ribbons and crystallites result from the fusion of neighboring ribbons due to cavitation effects.