A novel biomaterial: bacterial cellulose and its new era applications

Enzymatic Hydrolysis of Bacterial Cellulose for the Production of Nanocrystals for the Food Packaging Industry

Bacterial cellulose nanocrystals (BCNCs) obtained by enzymatic hydrolysis have been loaded in pullulan biopolymer for use as nanoparticles in the generation of high-oxygen barrier coatings intended for food packaging applications. Bacterial cellulose (BC) produced by Komagataeibacter sucrofermentans was hydrolyzed by two different enzymatic treatments, i.e., using endo-1,4-β-glucanases (EGs) from Thermobifida halotolerans and cellulase from Trichoderma reesei. The hydrolytic activity was compared by means of turbidity experiments over a period of 145 h, whereas BCNCs in their final state were compared, in terms of size and morphology, by atomic force microscopy (AFM) and dynamic light scattering (DLS). Though both treatments led to particles of similar size, a greater amount of nano-sized particles (≈250 nm) were observed in the system that also included cellulase enzymes. Unexpectedly, transmission electron microscopy (TEM) revealed that cellulose nanoparticles were round-shaped and made of 4–5 short (150–180 nm) piled whiskers. Pullulan/BCNCs nanocomposite coatings allowed an increase in the overall oxygen barrier performance, of more than two and one orders of magnitude (≈0.7 mL·m⁻²·24 h⁻¹), of pure polyethylene terephthalate (PET) (≈120 mL·m⁻²·24 h⁻¹) as well as pullulan/coated PET (≈6 mL·m⁻²·24 h⁻¹), with no significant difference between treatments (hydrolysis mediated by EGs or with the addition of cellulase). BCNCs obtained by enzymatic hydrolysis have the potential to generate high oxygen barrier coatings for the food packaging industry.

Microbial Nanocellulose Printed Circuit Boards for Medical Sensing

We demonstrate the viability of using ultra-thin sheets of microbially grown nanocellulose to build functional medical sensors. Microbially grown nanocellulose is an interesting alternative to plastics, as it is hydrophilic, biocompatible, porous, and hydrogen bonding, thereby allowing the potential development of new application routes. Exploiting the distinguishing properties of this material enables us to develop solution-based processes to create nanocellulose printed circuit boards, allowing a variety of electronics to be mounted onto our nanocellulose. As proofs of concept, we have demonstrated applications in medical sensing such as heart rate monitoring and temperature sensing-potential applications fitting the wide-ranging paradigm of a future where the Internet of Things is dominant.

Effect of Atomized Delivery of Nutrients on the Growth Characteristics and Microstructure Morphology of Bacterial Cellulose

This work demonstrates a general strategy for introducing remarkable changes in matrix organization and, consequently, functional properties of bacterial cellulose (BC). BC-producing cells were induced, using a well-defined atomized droplet nutrient delivery (ADND) system, to form pellicles with a regular layered morphology that persists throughout the mat depth. In contrast, the morphology of mats formed by conventional static medium nutrient delivery (SMND) is irregular with no distinguishable pattern. ADND also resulted in larger meso-scale average pore sizes but did not alter the fibril diameter (∼70 nm) and crystallinity index (92-95%). The specific modulus and specific tensile strength of ADND mats are higher than those of SMND mats. This is due to the regularity of dense layers that are present in ADND mats that are able to sustain tensile loads, when applied parallel to these layers. The density of BC films prepared by ADND is 1.63-fold lower than that of the SMND BC film. Consequently, the water contents (g/g) of ADND- and SMND-prepared BC mats are 263 ± 8.85 and 99.6 ± 2.04, respectively. A model that rationalizes differences in mat morphology resulting from these nutrient delivery methods based on nutrient and oxygen concentration gradients is proposed. This work raises questions as to the extent that ADND can be used to fine-tune the matrix morphology and how the resulting lower density mats will alter the diffusion of actives from the films to wound sites and increase the ability of cells to infiltrate the matrix during tissue engineering.

Genome sequencing and phylogenetic analysis of K1G4: a new Komagataeibacter strain producing bacterial cellulose from different carbon sources

OBJECTIVE

The objective of this study was to evaluate the ability of a new Komagataeibacter xylinus strain in producing bacterial cellulose from glucose, mannitol and glycerol, and to assess the genome sequencing with special focus on bacterial cellulose related genes.

RESULTS

Bacterial cellulose production during 9 days of cultivation was tested in glucose, mannitol and glycerol, respectively. Differences in the bacterial cellulose kinetic formation was observed, with a final yield of 9.47 g/L in mannitol, 8.30 g/L in glycerol and 7.57 g/L in glucose, respectively. The draft genome sequencing of K1G4 was produced, revealing a genome of 3.09 Mbp. Two structurally completed cellulose synthase operons and a third copy of the catalytic subunit of cellulose synthase were found. By using phylogenetic analysis, on the entire rRNA operon sequence, K1G4 was found to be closely related to Komagataeibacter xylinus LMG 1515^T and K. xylinus K2G30.

CONCLUSIONS

The different yields of bacterial cellulose produced on glucose, mannitol and glycerol can be correlated with the third copy of bcsAB operon harboured by K1G4, making it a versatile strain for industrial applications.

Soft Bacterial Cellulose Microcapsules with Adaptable Shapes

Microcapsules with controlled stability and permeability are in high demand for applications in separation and encapsulation. We have developed a biointerfacial process to fabricate strong, but flexible, porous microcapsules from bacterial cellulose at an oil-water emulsion interface. A broad range of microcapsule sizes has been successfully produced, from 100 μm to 5 cm in diameter. The three-dimensional capsule microstructure was imaged using confocal microscopy, showing a cellulose membrane thickness of around 30 μm that is highly porous, with some pores larger than 0.5 μm that are permeable to most macromolecules by free diffusion but can exclude larger structures like bacteria. The mechanical deformation of cellulose microcapsules reveals their flexibility, enabling them to pass through constrictions with a much smaller diameter than their initial size by bending and folding. Our work provides a new approach for producing soft, permeable, and biocompatible microcapsules for substance encapsulation and protection. The capsules may offer a replacement for suspended polymer beads in commercial applications and could potentially act as a framework for artificial cells.

Enzymatically Functionalized Composite Materials Based on Nanocellulose and Poly(Vinyl Alcohol) Cryogel and Possessing Antimicrobial Activity

In the present work, innovative composite biomaterials possessing bactericidal properties and based on the hexahistidine-tagged organophosphorus hydrolase (His₆-OPH) entrapped in the poly(vinyl alcohol) cryogel (PVA-CG)/bacterial cellulose (BC) were developed. His₆-OPH possesses lactonase activity, with a number of N-acyl homoserine lactones being the inducers of Gram-negative bacterial resistance. The enzyme can also be combined with various antimicrobial agents (antibiotics and antimicrobial peptides) to improve the efficiency of their action. In this study, such an effect was shown for composite biomaterials when His₆-OPH was entrapped in PVA-CG/BC together with β-lactam antibiotic meropenem or antimicrobial peptides temporin A and indolicidin. The residual catalytic activity of immobilized His₆-OPH was 60% or more in all the composite samples. In addition, the presence of BC filler in the PVA-CG composite resulted in a considerable increase in the mechanical strength and heat endurance of the polymeric carrier compared to the BC-free cryogel matrix. Such enzyme-containing composites could be interesting in the biomedical field to help overcome the problem of antibiotic resistance of pathogenic microorganisms.

Production with a High Yield of Bacterial Cellulose Nanocrystals by Enzymatic Hydrolysis

Bacterial cellulose nanocrystals are highly crystalline structures with nanoscopic scale dimensions that have received increased attention in the nanocomposites area. Its properties, such as large surface area, low density, mechanical strength and ease of modification, are attractive to the preparation many kinds of nanomaterials applied multifunctional in various fields. Besides, the cellulose nanocrystals are from abundant and renewable sources that are biodegradable. An altemative method is to obtain bacterial cellulose nanocrystal by enzymatic hydrolysis because it is, less expensive, it does not use chemicals and it requires much less energy. In this sense, the primary objective of this study was to produce bacterial cellulose using glycerol as a carbon source and isolate nanocrystals from bacterial cellulose using the enzymatic hydrolysis. This study also investigated the yield of nanocrystals depending on the weight of the bacterial cellulose hydrogel, keeping constant some enzymes. The study shows us that the enzymatic method has the best performance when using cellulose hydrogel 2[Formula: see text]g to 40[Formula: see text][Formula: see text]L cellulase enzyme (endoglucanase) and 1[Formula: see text]mL of citrate buffer. Also, it was observed that the yield of nanocrystals decrease with increasing time required for the hydrolysis.

Bacterial cellulose/phytochemical's extracts biocomposites for potential active wound dressings

The present study describes the impregnation of coffee extract (CE) into bacterial cellulose synthesized from kombucha tea fungus (KBC) of different cellulose content, incubated for different incubation periods (2, 4, and 10 days), to prepare biocomposites having the potential for wound healing applications. Total polyphenols in hydroalcoholic extracts from ground roasted coffee and its release from the prepared biocomposites were determined as gallic acid equivalent. The polyphenols content was found to be 13.66 mg/g and the minimum inhibitory concentration (MIC) of the CE was determined using colony-forming unit (CFU) method against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus where the growth inhibition was 86 and 97% respectively. Biocomposites (KBC/CE) with the lowest cellulose and CE content showed the highest wet tensile stress (3.35 MPa), absorption of pseudo extracellular fluid (154.32% ± 4.84), and water vapor transmission rate (3184.94 ± 198.07 g/m²/day), whereas it showed the lowest polyphenols' release (51.85% ± 2.94)when immersed in PBS buffer of pH 7.4. The impregnation of CE into KBC provided biocomposites that can enlarge the range of BC in the biomedical application.

Bacterial nanocellulose: Present status, biomedical applications and future perspectives

Bacterial nanocellulose (BNC) has emerged as a natural biopolymer of significant importance in diverse technological areas due to its incredible physicochemical and biological characteristics. However, the high capital investments, production cost and lack of well-organized scale-up processes resulting in low BNC production are the major impediments need to be resolved. This review enfolds the three different and important portions of BNC. Firstly, advancement in production technologies of BNC like cell-free extract technology, static intermittent fed batch technology and novel cost-effective substrates that might surmount the barriers associated with BNC production at industrial level. Secondly, as BNC and its composites (with other polymers/nanoparticles) represents the utmost material of preference in current regenerative and diagnostic medicine, therefore recently reported biomedical applications of BNC and functionalized BNC in drug delivery, tissue engineering, antimicrobial wound healing and biosensing are widely been focused here. The third and the most important aspect of this review is an in-depth discussion of various pitfalls associated with BNC production. Recent trends in BNC research to overcome the existing snags that might pave a way for industrial scale production of BNC thereby facilitating its feasible application in various fields are highlighted.

Functional cellulose-based hydrogels as extracellular matrices for tissue engineering

Cellulose-based hydrogels are immensely important for tissue engineering. In this review, we attempt to document the source, nature, and application of cellulose-based hydrogels as an extracellular matrix for tissue growth and regeneration. Hydrogels can be prepared either from native cellulose, including both bacterial and plant sources or from cellulose derivatives, such as methyl cellulose, carboxymethylcellulose, and hydroxypropylmethylcellulose or even metal ions such as silver. Cellulose-polymer composite (polymers that include natural sources including chitosan, starch, alginates, collagen, hyaluronic acid, and chitin) are an attractive, inexpensive, and advantageous structural material that is easy to use. Cellulose-based scaffolding materials are widely used in the regeneration of various tissues, such as bone, cartilage, heart, blood vessel, nerve, and liver, among others. In this review, we discuss the most important applications of cellulosic hydrogels in tissue engineering based on their structural compositions.

Bacterial cellulose production, properties and applications with different culture methods - A review

Bacterial cellulose (BC) is an organic compound produced by certain types of bacteria. In natural habitats, the majority of bacteria synthesize extracellular polysaccharides, such as cellulose, which form protective envelopes around the cells. Many methods are currently being investigated to enhance cellulose growth. The various celluloses produced by different bacteria possess different morphologies, structures, properties, and applications. However, the literature lacks a comprehensive review of the different methods of BC production, which are critical to BC properties and their final applications. The aims of this review are to provide an overview of the production of BC from different culture methods, to analyze the characteristics of particular BC productions, to indicate existing problems associated with different methods, and to choose suitable culture approaches for BC applications in different fields. The main goals for future studies have also been discussed here.

TEMPO oxidized nano-cellulose containing thermo-responsive injectable hydrogel for post-surgical peritoneal tissue adhesion prevention

The objective of this study was to present an effective injectable adhesion barrier comprised of TEMPO-oxidized cellulose nanofiber (TOCN), methyl cellulose, carboxymethyl cellulose, and polyethylene glycol. Hydrogels with different concentrations (0.2, 0.5, 0.8, 1% w/v) of bio compatible TOCN were investigated to determine their abilities to prevent post-surgical peritoneal adhesion using a rat cecal wall abrasion model. Sol-gel transition at body temperature (37 °C) was optimized by adjusting concentration of sodium ions (Na⁺), with a gelation time of 45 ± 7 s. These TOCN containing hydrogels showed non cytotoxicity to rat bone marrow mesenchymal stem cells (RBMSCs) and L929 fibroblast cells as cell models during in vitro assessment. Degradation studies revealed that, TOCN concentration in hydrogel was inversely proportional to hydrolytic degradation rate. From in vivo evaluations, TOCN 0.2 hydrogel significantly reduced peritoneal adhesion in rat (n = 8) compared to untreated controls based on gross observation, histological analysis, and expression analysis of marker proteins. By taking advantages of thermo gelling, high stability, non-invasive way of application and rapid recovery potential, TOCN containing bio compatible hydrogel could be used as a cost-effective barrier to efficiently inhibit post-surgical peritoneal adhesions.

Comparison of productivity and quality of bacterial nanocellulose synthesized using culture media based on seven sugars from biomass

Komagataeibacter xylinus ATCC 23770 was statically cultivated in eight culture media based on different carbon sources, viz. seven biomass‐derived sugars and one sugar mixture. The productivity and quality of the bacterial nanocellulose (BNC) produced in the different media were compared. Highest volumetric productivity, yield on consumed sugar, viscometric degree of polymerization (DP_v, 4350–4400) and thermal stability were achieved using media based on glucose or maltose. Growth in media based on xylose, mannose or galactose resulted in lower volumetric productivity and DP_v, but in larger fibril diameter and higher crystallinity (76–78%). Growth in medium based on a synthetic sugar mixture resembling the composition of a lignocellulosic hydrolysate promoted BNC productivity and yield, but decreased fibril diameter, DP_v, crystallinity and thermal stability. This work shows that volumetric productivity, yield and properties of BNC are highly affected by the carbon source, and indicates how industrially relevant sugar mixtures would affect these characteristics.

Cellulose Biomaterials for Tissue Engineering

In this review, we highlight the importance of nanostructure of cellulose-based biomaterials to allow cellular adhesion, the contribution of nanostructure to macroscale mechanical properties, and several key applications of these materials for fundamental scientific research and biomedical engineering. Different features on the nanoscale can have macroscale impacts on tissue function. Cellulose is a diverse material with tunable properties and is a promising platform for biomaterial development and tissue engineering. Cellulose-based biomaterials offer some important advantages over conventional synthetic materials. Here we provide an up-to-date summary of the status of the field of cellulose-based biomaterials in the context of bottom-up approaches for tissue engineering. We anticipate that cellulose-based material research will continue to expand because of the diversity and versatility of biochemical and biophysical characteristics highlighted in this review.

Combining Stem Cells and Biomaterial Scaffolds for Constructing Tissues and Cell Delivery

Combining stem cells with biomaterial scaffolds serves as a promising strategy for engineering tissues for both in vitro and in vivo applications. This updated review details commonly used biomaterial scaffolds for engineering tissues from stem cells. We first define the different types of stem cells and their relevant properties and commonly used scaffold formulations. Next, we discuss natural and synthetic scaffold materials typically used when engineering tissues, along with their associated advantages and drawbacks and gives examples of target applications. New approaches to engineering tissues, such as 3D bioprinting, are described as they provide exciting opportunities for future work along with current challenges that must be addressed. Thus, this review provides an overview of the available biomaterials for directing stem cell differentiation as a means of producing replacements for diseased or damaged tissues.

Three Years' Experience of a Novel Biosynthetic Cellulose Dressing in Burns

Objective: The use of porcine xenograft (PX) is widely spread in burn care. However, it may cause immunologic responses and other ethical and cultural considerations in different cultures. Therefore, there is a need for alternatives. The aim of this work is to test a novel biosynthetic cellulose dressing (Epiprotect^®) on burn patients.

Approach: Charts from 38 patients with superficial burns (SBs) (n = 18) or excised burns (n = 20) that got biosynthetic cellulose dressing instead of PX at a national burn center during 3 years were reviewed. Time to healing, length of stay, and wound infection were extracted from the medical records.

Results: SBs hospitalization time was 11 days comparable to PXs reported by others. In the excised group, median duration of hospital stay was 35 days. Time to healing was 28 days. Seven wound infections were confirmed in the superficial group (39%) and 11 infections in the excised group (61%). Patients with superficial wounds reported pain relief on application.

Innovation: A dressing (17 × 21 cm) consisting of biosynthetic cellulose replacing PX.

Conclusion: Outcome of treatment of SBs or temporary coverage of excised deep burns with biosynthetic cellulose is comparable to treatment with PX. However, biosynthetic cellulose has benefits such as providing pain relief on application and ethical or cultural issues with the material is nonexistent.

Micro-/Nano-Scales Direct Cell Behavior on Biomaterial Surfaces

Cells are the smallest living units of a human body's structure and function, and their behaviors should not be ignored in human physiological and pathological metabolic activities. Each cell has a different scale, and presents distinct responses to specific scales: Vascular endothelial cells may obtain a normal function when regulated by the 25 µm strips, but de-function if the scale is removed; stem cells can rapidly proliferate on the 30 nm scales nanotubes surface, but stop proliferating when the scale is changed to 100 nm. Therefore, micro and nano scales play a crucial role in directing cell behaviors on biomaterials surface. In recent years, a series of biomaterials surface with micro and/or nano scales, such as micro-patterns, nanotubes and nanoparticles, have been developed to control the target cell behavior, and further enhance the surface biocompatibility. This contribution will introduce the related research, and review the advances in the micro/nano scales for biomaterials surface functionalization.

Stable composite of bacterial nanocellulose and perforated polypropylene mesh for biomedical applications

The article presents the method of preparation of new, stable bacterial cellulose composites with perforated solid materials for biomedical applications, comprising reconstructive surgery of soft and hard tissues. The composites were obtained in specially designed bioreactors equipped with a set of perforated mesh stripes threaded vertically to the culture medium, ensuring perpendicular growth of bacterial nanocellulose synthesized by Komagataeibacter xylinus E₂₅ in stationary culture. The developed biocomposites have been tested for stability and mechanical strength, as well as for their in vitro inflammatory responses shown as mast cell degranulation with N-acetyl-β-d-hexosaminidase release and mast cell adhesion. The obtained results indicate that the composites components are well integrated after the process of cultivation and purification. Bacterial nanocellulose does not negatively influence mechanical properties of the polypropylene porous mesh, preserving its tensile strength, elasticity, and load. Moreover, application of bacterial cellulose makes the composites less immunogenic as compared to polypropylene itself. Therefore, the composites have the great potential of application in medicine, and depending on the applied porous material, might be used either in hernioplasty (if porous hernia mesh is used), cranioplasty (if perforated metal or polymeric cranial implant is applied), or as a protective barrier in any application that requires biocompatibility or antiadhesive properties improvement. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 978-987, 2019.

Understanding Kombucha Tea Fermentation: A Review

Kombucha is a beverage of probable Manchurian origins obtained from fermented tea by a microbial consortium composed of several bacteria and yeasts. This mixed consortium forms a powerful symbiosis capable of inhibiting the growth of potentially contaminating bacteria. The fermentation process also leads to the formation of a polymeric cellulose pellicle due to the activity of certain strains of Acetobacter sp. The tea fermentation process by the microbial consortium was able to show an increase in certain biological activities which have been already studied; however, little information is available on the characterization of its active components and their evolution during fermentation. Studies have also reported that the use of infusions from other plants may be a promising alternative.

PRACTICAL APPLICATION

Kombucha is a traditional fermented tea whose consumption has increased in the recent years due to its multiple functional properties such as anti-inflammatory potential and antioxidant activity. The microbiological composition of this beverage is quite complex and still more research is needed in order to fully understand its behavior. This study comprises the chemical and microbiological composition of the tea and the main factors that may affect its production.

Study on the Use of Microbial Cellulose as a Biocarrier for 1,3-Dihydroxy-2-Propanone and Its Potential Application in Industry

Can microbial cellulose (MC) be used as a bio-carrier for 1,3-dihydroxy-2-propanone (DHA)? The aim of this study was to examine the possibility of using MC as a biomaterial for DHA transferring into the stratum corneum and inducing changes in skin color. The MC patches were obtained from Gluconacetobacter xylinus strain and incubated in solutions with various concentrations of DHA (g·L⁻¹: 20; 50; 80; 110) at 22 °C for 24 h. Afterwards; the patches were applied onto the skin for 15, 30, or 60 min. Skin color changes were assessed visually compared to a control patches without DHA. The intensity of skin color was increasing with the increase of DHA concentration and time of patches application. Application of MC patches with DHA (50 g·L⁻¹) for 30 min ensured the color which was considered the closest to the desired natural tan effect. MC patches containing DHA can be biocarriers enabling DHA transport into the stratum corneum and causing skin color changes. Study results indicate a new possibility for industrial applications of MC; e.g., as a biocarrier in masking the symptoms of vitiligo or production of self-tanning agents in the form of masks.

Cost-effective production of bacterial cellulose using acidic food industry by-products

To reduce the cost of obtaining bacterial cellulose, acidic by-products of the alcohol and dairy industries were used without any pretreatment or addition of other nitrogen sources. Studies have shown that the greatest accumulation of bacterial cellulose (6.19 g/L) occurs on wheat thin stillage for 3 days of cultivation under dynamic conditions, which is almost 3 times higher than on standard Hestrin and Schramm medium (2.14 g/L). The use of whey as a nutrient medium makes it possible to obtain 5.45 g/L bacterial cellulose under similar conditions of cultivation. It is established that the pH of the medium during the growth of Gluconacetobacter sucrofermentans B-11267 depends on the feedstock used and its initial value. By culturing the bacterium on thin stillage and whey, there is a decrease in the acidity of the waste. It is shown that the infrared spectra of bacterial cellulose obtained in a variety of environments have a similar character, but we found differences in the micromorphology and crystallinity of the resulting biopolymer.

“Deceived” Concentrated Immobilized Cells as Biocatalyst for Intensive Bacterial Cellulose Production from Various Sources

A new biocatalyst in the form of Komagataeibacter xylinum B-12429 cells immobilized in poly(vinyl alcohol) cryogel for production of bacterial cellulose was demonstrated. Normally, the increased bacteria concentration causes an enlarged bacterial cellulose synthesis while cells push the polysaccharide out to pack themselves into this polymer and go into a stasis. Immobilization of cells into the poly(vinyl alcohol) cryogel allowed “deceiving” them: bacteria producing cellulose pushed it out, which further passed through the pores of cryogel matrix and was accumulated in the medium while not covering the cells; hence, the latter were deprived of a possible transition to inactivity and worked on the synthesis of bacterial cellulose even more actively. The repeated use of immobilized cells retaining 100% of their metabolic activity for at least 10 working cycles (60 days) was performed. The immobilized cells produce bacterial cellulose with crystallinity and porosity similar to polysaccharide of free cells, but having improved stiffness and tensile strength. Various media containing sugars and glycerol, based on hydrolysates of renewable biomass sources (aspen, Jerusalem artichoke, rice straw, microalgae) were successfully applied for bacterial cellulose production by immobilized cells, and the level of polysaccharide accumulation was 1.3–1.8-times greater than suspended cells could produce.

Biotransformation of sweet lime pulp waste into high-quality nanocellulose with an excellent productivity using Komagataeibacter europaeus SGP37 under static intermittent fed-batch cultivation

Herein, sweet lime pulp waste (SLPW) was utilized as a low- or no-cost feedstock for the production of bacterial nanocellulose (BNC) alone and in amalgamation with other nutritional supplements by the isolate K. europaeus SGP37 under static batch and static intermittent fed-batch cultivation. The highest yield (26.2±1.50gL^-1) was obtained in the hot water extract of SLPW supplemented with the components of HS medium, which got further boosted to 38±0.85gL^-1 as the cultivation strategy was shifted from static batch to static intermittent fed-batch. BNC obtained from various SLPW medium was similar or even superior to that obtained with standard HS medium in terms of its physicochemical properties. The production yields of BNC thus obtained are significantly higher and fit well in terms of industrial scale production.

Bacterial Cellulose Ionogels as Chemosensory Supports

To fully leverage the advantages of ionic liquids for many applications, it is necessary to immobilize or encapsulate the fluids within an inert, robust, quasi-solid-state format that does not disrupt their many desirable, inherent features. The formation of ionogels represents a promising approach; however, many earlier approaches suffer from solvent/matrix incompatibility, optical opacity, embrittlement, matrix-limited thermal stability, and/or inadequate ionic liquid loading. We offer a solution to these limitations by demonstrating a straightforward and effective strategy toward flexible and durable ionogels comprising bacterial cellulose supports hosting in excess of 99% ionic liquid by total weight. Termed bacterial cellulose ionogels (BCIGs), these gels are prepared using a facile solvent-exchange process equally amenable to water-miscible and water-immiscible ionic liquids. A suite of characterization tools were used to study the preliminary (thermo)physical and structural properties of BCIGs, including no-deuterium nuclear magnetic resonance, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and X-ray diffraction. Our analyses reveal that the weblike structure and high crystallinity of the host bacterial cellulose microfibrils are retained within the BCIG. Notably, not only can BCIGs be tailored in terms of shape, thickness, and choice of ionic liquid, they can also be designed to host virtually any desired active, functional species, including fluorescent probes, nanoparticles (e.g., quantum dots, carbon nanotubes), and gas-capture reagents. In this paper, we also present results for fluorescent designer BCIG chemosensor films responsive to ammonia or hydrogen sulfide vapors on the basis of incorporating selective fluorogenic probes within the ionogels. Additionally, a thermometric BCIG hosting the excimer-forming fluorophore 1,3-bis(1-pyrenyl)propane was devised which exhibited a ratiometric (two-color) fluorescence output that responded precisely to changes in local temperature. The ionogel approach introduced here is simple and has broad generality, offering intriguing potential in (bio)analytical sensing, catalysis, membrane separations, electrochemistry, energy storage devices, and flexible electronics and displays.

Crystal structure of the flexible tandem repeat domain of bacterial cellulose synthesis subunit C

Bacterial cellulose (BC) is synthesized and exported through the cell membrane via a large protein complex (terminal complex) that consists of three or four subunits. BcsC is a little-studied subunit considered to export BC to the extracellular matrix. It is predicted to have two domains: a tetratrico peptide repeat (TPR) domain and a β-barrelled outer membrane domain. Here we report the crystal structure of the N-terminal part of BcsC-TPR domain (Asp24-Arg272) derived from Enterobacter CJF-002. Unlike most TPR-containing proteins which have continuous TPR motifs, this structure has an extra α-helix between two clusters of TPR motifs. Five independent molecules in the crystal had three different conformations that varied at the hinge of the inserted α-helix. Such structural feature indicates that the inserted α-helix confers flexibility to the chain and changes the direction of the TPR super-helix, which was also suggested by structural analysis of BcsC-TPR (Asp24-Leu664) in solution by size exclusion chromatography-small-angle X-ray scattering. The flexibility at the α-helical hinge may play important role for exporting glucan chains.

The optimization of fermentation conditions for producing cellulase of Bacillus amyloliquefaciens and its application to goose feed

The proper culture conditions for producing cellulase of Bacillus amyloliquefaciens S1, isolated from the cecum of goose was optimized by single-factor experiment combined with orthogonal test. The properties of the cellulase were investigated by DNS method. The appropriate doses of B. amyloliquefaciens S1 were obtained by adding them to goose feed. It indicated that the suitable culture conditions of producing cellulase were the culture temperature of 37°C, the initial pH of 7.0, the incubation time of 72 h and the loaded liquid volume of 75 ml per 250 ml. The effects of each factor on producing cellulase by B. amyloliquefaciens S1 were as follows: initial pH > incubation time = culture temperature > loaded liquid volume. The optimum reaction temperature and pH were 50°C and 7.0, respectively. This enzyme is a kind of neutral cellulase that possesses resistance to heat and acidity. It showed high activity to absorbent cotton, soya bean meal and filter paper. By adding different doses of B. amyloliquefaciens S1 to the goose feed, it was found that the egg production, average egg weight, fertilization rate and the hatching rate were promoted both in experiment 1 (1.5 g kg-1) and experiment 2 (3 g kg-1). Also the difference of egg production, fertilization rate and hatching rate between experiment 1 and control group was obvious (p < 0.05), and the average egg weight was significantly increased in experiment 2 (p < 0.05).

Bioconversion of Waste Fiber Sludge to Bacterial Nanocellulose and Use for Reinforcement of CTMP Paper Sheets

Utilization of bacterial nanocellulose (BNC) for large-scale applications is restricted by low productivity in static cultures and by the high cost of the medium. Fiber sludge, a waste stream from pulp and paper mills, was enzymatically hydrolyzed to sugar, which was used for the production of BNC by the submerged cultivation of Komagataeibacter xylinus. Compared with a synthetic glucose-based medium, the productivity of purified BNC from the fiber sludge hydrolysate using shake-flasks was enhanced from 0.11 to 0.17 g/(L × d), although the average viscometric degree of polymerization (DP_v) decreased from 6760 to 6050. The cultivation conditions used in stirred-tank reactors (STRs), including the stirring speed, the airflow, and the pH, were also investigated. Using STRs, the BNC productivity in fiber-sludge medium was increased to 0.32 g/(L × d) and the DP_v was increased to 6650. BNC produced from the fiber sludge hydrolysate was used as an additive in papermaking based on the chemithermomechanical pulp (CTMP) of birch. The introduction of BNC resulted in a significant enhancement of the mechanical strength of the paper sheets. With 10% (w/w) BNC in the CTMP/BNC mixture, the tear resistance was enhanced by 140%. SEM images showed that the BNC cross-linked and covered the surface of the CTMP fibers, resulting in enhanced mechanical strength.

Production and Status of Bacterial Cellulose in Biomedical Engineering

Bacterial cellulose (BC) is a highly pure and crystalline material generated by aerobic bacteria, which has received significant interest due to its unique physiochemical characteristics in comparison with plant cellulose. BC, alone or in combination with different components (e.g., biopolymers and nanoparticles), can be used for a wide range of applications, such as medical products, electrical instruments, and food ingredients. In recent years, biomedical devices have gained important attention due to the increase in medical engineering products for wound care, regeneration of organs, diagnosis of diseases, and drug transportation. Bacterial cellulose has potential applications across several medical sectors and permits the development of innovative materials. This paper reviews the progress of related research, including overall information about bacterial cellulose, production by microorganisms, mechanisms as well as BC cultivation and its nanocomposites. The latest use of BC in the biomedical field is thoroughly discussed with its applications in both a pure and composite form. This paper concludes the further investigations of BC in the future that are required to make it marketable in vital biomaterials.

Ultrasound-assisted swelling of bacterial cellulose

Bacterial cellulose (BC) was obtained by static cultivation using commercial BC gel from scoby. BC membranes (oven dried and freeze-dried) were swelled with 8% NaOH, in the absence and in the presence of ultrasound (US), for 30, 60, and 90 min. The influence of swelling conditions on both physico-chemical properties and molecules entrapment was evaluated. Considering the highest levels of entrapment, an optimum swelling procedure was established: 8% NaOH for 30 min at room temperature in the presence of US. Native and PEGylated laccase from Myceliophthora thermophila was immobilized on BC membranes and a different catalytic behaviour was observed after immobilization. Native laccase presented activity values similar to published reports (5-7 U/gBC) after immobilization whereas PEGylated enzymes showed much lower activity (1-2 U/gBC). BC swelled membranes are presented herein as a potential support for the preparation of immobilized enzymes for industrial applications, like phenolics polymerization.

Versatile modes of cellular regulation via cyclic dinucleotides

Since the discovery of c-di-GMP almost three decades ago, cyclic dinucleotides (CDNs) have emerged as widely used signaling molecules in most kingdoms of life. The family of second messengers now includes c-di-AMP and distinct versions of mixed cyclic GMP-AMP (cGAMP) compounds. In addition to these nucleotides, a vast number of proteins for the production and turnover of these molecules have been described, as well as effectors that translate the signals into physiological responses. The latter include, but are not limited to, mechanisms for adaptation and survival in prokaryotes, persistence and virulence of bacterial pathogens, and immune responses to viral and bacterial invasion in eukaryotes. In this review, we will focus on recent discoveries and emerging themes that illustrate the ubiquity and versatility of cyclic dinucleotide function at the transcriptional and post-translational levels and, in particular, on insights gained through mechanistic structure-function analyses.

Bacterial cellulose production by Komagataeibacter hansenii using algae-based glucose

Bacterial cellulose (BC) is a homopolymer and it is distinguished from plant-based cellulose by its unique properties such as high purity, high crystallinity, high water-holding capacity, and good biocompatibility. Microalgae are unicellular, photosynthetic microorganisms and are known to have high protein, starch, and oil content. In this study, Chlorella vulgaris was evaluated as source of glucose for the production of BC. To increase the starch content of algae the effect of nutrient starvation (nitrogen and sulfur) and light deficiency were tested in a batch assay. The starch contents (%) were 5.27 ± 0.04, 7.14 ± 0.18, 5.00 ± 0.08, and 1.35 ± 0.04 for normal cultivation, nitrogen starvation, sulfur starvation, and dark cultivation conditions, respectively. The performance of enzymatic and acidic methods was compared for the starch hydrolysis. This study demonstrated for the first time that acid hydrolysate of algal starch can be used to substitute glucose in the fermentation medium of Komagataeibacter hansenii for BC production. Glucose was used as a control for BC production. BC production yields on dry weight basis were 1.104 ± 0.002 g/L and 1.202 ± 0.005 g/L from algae-based glucose and glucose, respectively. The characterization of both BCs produced from glucose and algae-based glucose was investigated by scanning electron microscopy and Fourier transform infrared spectroscopy. The results have shown that the structural characteristics of algae-based BC were comparable to those of glucose-based BC.

The role of cellulose nanocrystals incorporation route in waterborne polyurethane for preparation of electrospun nanocomposites mats

Electrospinning offers the possibility of obtaining fibers mats from polymer solutions. The use of environmentally-friendly waterborne polyurethane (WBPU) allows obtaining electrospun polyurethane mats in water medium. Furthermore, the incorporation of water dispersible nanoentities, like renewable cellulose nanocrystals (CNC), is facilitated. Therefore, in this work, a WBPU was synthesized and CNC were isolated for preparing WBPU-CNC dispersions nanocomposites with 1 and 3wt% of CNC following both the classical mixing by sonication, and the innovative in-situ route. The dispersions were used for obtaining electrospun mats assisted by poly(ethylene oxide) (PEO) as polymer template. Moreover, the extraction of PEO with water resulted in continuous WBPU-CNC mats, showing different properties respect to WBPU-CNC mats containing PEO. The effective addition of CNC led to more defined cylindrical morphologies and the two alternative incorporation routes induced to different CNC dispositions in the matrix, which modified fibers diameters, and thus, mats final properties.

Laccase immobilization on bacterial nanocellulose membranes: Antimicrobial, kinetic and stability properties

This work studied the physical immobilization of a commercial laccase on bacterial nanocellulose (BNC) aiming to identify the laccase antibacterial properties suitable for wound dressings. Physico-chemical analysis demonstrates that the BNC structure is manly formed by pure crystalline Iα cellulose. The pH optimum and activation energy of free laccase depends on the substrate employed corresponding to pH 6, 7, 3 and 57, 22, 48kJmol(-1) for 2,6-dimethylphenol (DMP), catechol and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), respectively. The Michaelis-Menten constant (Km) value for the immobilized laccase (0.77mM) was found to be almost double of that of the free enzyme (0.42mM). However, the specific activities of immobilized and free laccase are similar suggesting that the cage-like structure of BNC allows entrapped laccase to maintain some flexibility and favour substrate accessibility. The results clearly show the antimicrobial effect of laccase in Gram-positive (92%) and Gram-negative (26%) bacteria and cytotoxicity acceptable for wound dressing applications.