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From nature to lab : sustainable bacterial cellulose production and modification with synthetic biology
Vid Potočnik, Selestina Gorgieva, Janja Trček, 2023, review article

Abstract: Bacterial cellulose (BC) is a macromolecule with versatile applications in medicine, pharmacy, biotechnology, cosmetology, food and food packaging, ecology, and electronics. Although many bacteria synthesize BC, the most efficient BC producers are certain species of the genera Komagataeibacter and Novacetimonas. These are also food-grade bacteria, simplifying their utilization at industrial facilities. The basic principles of BC synthesis are known from studies of Komagataeibacter xylinus, which became a model species for studying BC at genetic and molecular levels. Cellulose can also be of plant origin, but BC surpasses its purity. Moreover, the laboratory production of BC enables in situ modification into functionalized material with incorporated molecules during its synthesis. The possibility of growing Komagataeibacter and Novacetimonas species on various organic substrates and agricultural and food waste compounds also follows the green and sustainable economy principles. Further intervention into BC synthesis was enabled by genetic engineering tools, subsequently directing it into the field of synthetic biology. This review paper presents the development of the fascinating field of BC synthesis at the molecular level, seeking sustainable ways for its production and its applications towards genetic modifications of bacterial strains for producing novel types of living biomaterials using the flexible metabolic machinery of bacteria.
Keywords: acetic acid bacteria, bacterial cellulose, sustainable production, agricultural waste, food waste, genetic engineering, synthetic biology, biomaterial, Komagataeibacter, Novacetimonas
Published in DKUM: 28.03.2024; Views: 74; Downloads: 10
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5.
Cationised fibre-based cellulose multi-layer membranes for sterile and high-flow bacteria retention and inactivation
Vanja Kokol, Monika Kos, Vera Vivod, Nina Gunde-Cimerman, 2023, original scientific article

Abstract: Low-cost, readily available, or even disposable membranes in water purification or downstream biopharma processes are becoming attractive alternatives to expensive polymeric columns or filters. In this article, the potential of microfiltration membranes prepared from differently orientated viscose fibre slivers, infused with ultrafine quaternised (qCNF) and amino-hydrophobised (aCNF) cellulose nanofibrils, were investigated for capturing and deactivating the bacteria from water during vacuum filtration. The morphology and capturing mechanism of the single- and multi-layer structured membranes were evaluated using microscopic imaging and colloidal particles. They were assessed for antibacterial efficacy and the retention of selected bacterial species (Escherichia coli, Staphylococcus aureus, Micrococcus luteus), differing in the cell envelope structure, hydrodynamic biovolume (shape and size) and their clustering. The aCNF increased biocidal efficacy significantly when compared to qCNF-integrated membrane, although the latter retained bacteria equally effectively by a thicker multi-layer structured membrane. The retention of bacterial cells occurred through electrostatic and hydrophobic interactions, as well as via interfibrous pore diffusion, depending on their physicochemical properties. For all bacterial strains, the highest retention (up to 100% or log 6 reduction) at >50 L/h∗bar∗m2 flow rate was achieved with a 4-layer gradient-structured membrane containing different aCNF content, thereby matching the performance of industrial polymeric filters used for removing bacteria.
Keywords: fibrous membrane, cationised cellulose nanofibrils, amino-hydrophobised cellulose nanofibrils, antibacterial activity, multi-layer structure, flux, bacteria retention
Published in DKUM: 28.03.2024; Views: 56; Downloads: 0
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6.
GO-enabled bacterial cellulose membranes by multistep, in situ loading : effect of bacterial strain and loading pattern on nanocomposite properties
Tobiasz Gabryś, Beata Fryczkowska, Urška Jančič, Janja Trček, Selestina Gorgieva, 2023, original scientific article

Abstract: This paper presents the results of research on the preparation and properties of GO/BC nanocomposite from bacterial cellulose (BC) modified with graphene oxide (GO) using the in situ method. Two bacterial strains were used for the biosynthesis of the BC: Komagataeibacter intermedius LMG 18909 and Komagataeibacter sucrofermentans LMG 18788. A simple biosynthesis method was developed, where GO water dispersion was added to reinforced acetic acid-ethanol (RAE) medium at concentrations of 10 ppm, 25 ppm, and 50 ppm at 24 h and 48 h intervals. As a result, a GO/BC nanocomposite membrane was obtained, characterized by tensile strength greater by 150% as compared with the pure BC (̴ 50 MPa) and lower volume resistivity of ~4 ∙ 109 Ω × cm. Moreover, GO addition increases membrane thickness up to ~10% and affects higher mass production, especially with low GO concentration. All of this may indicate the possibility of using GO/BC membranes in fuel cell applications.
Keywords: bacterial cellulose, graphene oxide, nanocomposite, structural analysis
Published in DKUM: 13.03.2024; Views: 115; Downloads: 6
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7.
Cellulose nanofibrils-reinforced pectin membranes for the adsorption of cationic dyes from a model solution
Alenka Ojstršek, Selestina Gorgieva, 2024, original scientific article

Abstract: In the presented research, a facile, one-step method for the fabrication of cellulose nanofibrils/pectin (CNFs/PC) membranes is described, which were tested further for their ability to remove cationic dyes from the prepared model solutions. For this purpose, ten membranes were prepared with different quantities of CNFs and PC with/without citric acid (CA) or CaCl2 as mediated crosslinking agents, and they were characterised comprehensively in terms of their physical, chemical, and hydrophilic properties. All the prepared CNFs/PC membranes were hydrophilic with a Water Contact Angle (WCA) from 51.23◦ (without crosslinker) up to 78.30◦ (CaCl2 ) and swelling of up to 485% (without crosslinker), up to 437% (CaCl2 ) and up to 270% (CA). The stability of membranes was decreased with the increase in PC; thus, only four membranes (M1, M2, M3 and M5) were stable enough in water after 24 h, and these were additionally applied in the adsorption trials, using two structurally different cationic dyes, i.e., C.I. Basic Yellow 28 (BY28) and C.I. Basic Blue 22 (BB22), in four concentrations. The highest total surface charge of M3 (2.83 mmol/g) as compared to the other membranes influenced the maximal removal efficiency of both dyes, up to 37% (BY28) and up to 71% (BB22), depending on the initial dye concentration. The final characteristics of the membranes and, consequently, the dye’s absorption ability could be tuned easily by changing the ratio between the CNFs and PC, as well as the type and amount of crosslinker.
Keywords: cellulose nanofibrils, pectin, cationic dyes, adsorption, dye removal
Published in DKUM: 12.03.2024; Views: 107; Downloads: 4
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8.
Cellulose–chitosan functional biocomposites
Simona Strnad, Lidija Fras Zemljič, 2023, review article

Abstract: Here, we present a detailed review of recent research and achievements in the field of combining two extremely important polysaccharides; namely, cellulose and chitosan. The most important properties of the two polysaccharides are outlined, giving rise to the interest in their combination. We present various structures and forms of composite materials that have been developed recently. Thus, aerogels, hydrogels, films, foams, membranes, fibres, and nanofibres are discussed, alongside the main techniques for their fabrication, such as coextrusion, co-casting, electrospinning, coating, and adsorption. It is shown that the combination of bacterial cellulose with chitosan has recently gained increasing attention. This is particularly attractive, because both are representative of a biopolymer that is biodegradable and friendly to humans and the environment. The rising standard of living and growing environmental awareness are the driving forces for the development of these materials. In this review, we have shown that the field of combining these two extraordinary polysaccharides is an inexhaustible source of ideas and opportunities for the development of advanced functional materials.
Keywords: biocomposites, functional materials, cellulose–chitosan, fibers, films, hydrogels, nanofibers
Published in DKUM: 19.02.2024; Views: 120; Downloads: 17
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9.
Functional 3D printed polysaccharide derivative scaffolds for vascular graft application : doctoral disertation
Fazilet Gürer, 2023, doctoral dissertation

Abstract: Tissue engineering (TE) is an interdisciplinary field that aims towards replacement, healing or reconstruction of damaged tissue and organs. Incurable diseases are currently treated with organ transplantation, that have the disadvantages of insufficient donors, immune response, and organ rejection after transplantation. TE imitate the functions of extracellular matrix (ECM) to develop biocompatible/biodegradable scaffolds with appropriate features which are utilized to provide mechanical support, cellular infiltration, migration, and tissue formation, and to mimic the biochemical and biophysical cues of cells. Several fabrication methods have been introduced to mimic the 3D structure of ECM and 3D printing is one of the additive manufacturing techniques, widely used in TE because of its feasibility to build complex tissue constructs and control over fabrication and cell distribution. The polysaccharide-peptide conjugate has gained enormous interest in recent years owing to its biocompatibility, degradability, flexibility, and structural matching to natural proteoglycans. In this context, we reported here on investigation of biocompatibility with HUVECs, surface modification of 3D printed PCL scaffolds with an amine group and chemically crosslinked oxidized HA-amino acid/peptide conjugates (OHACs) was used to develop a novel biomaterial for use as a tissue engineered vascular graft. Modified polysaccharides were characterized with respect to their chemical structure, charge, UV and fluorescence properties and cytotoxicity. The successful conjugation was demonstrated by XPS, and a decrease in the free amine peaks on the surface was observed after conjugation. In addition, the water contact angle measurements showed improved wetting, an indication that the conjugation to the PCL-A surface was successful. Finally, the biocompatibility of the novel scaffolds was characterized by the MTS and the live- dead assay. In both assays, proliferation of cells was observed after 7 days and cell spreading on the surface was detected by phalloidin staining of actin filaments. In conclusion, it was possible to prepare surface-active scaffolds by combining the advantages of biocompatibility and mechanical strength of polysaccharides and polyesters, respectively.
Keywords: 3D tiskanje, karboksimetilceluloza, hialuronska kislina, polikaprolakton, kemija karbodiimida, kemija Shiffove baze, endotelizacija 3D printing, carboxymethyl cellulose, hyaluronic acid, polycaprolactone, carbodiimide chemistry, shiff-base chemistry, endothelialization
Published in DKUM: 06.10.2023; Views: 309; Downloads: 37
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10.
Optimization of conditions for enzymatic decomposition of fibrous cotton textile waste : diplomsko delo univerzitetnega študijskega programa I. stopnje
Stela Tashkova, 2023, undergraduate thesis

Abstract: The main goal of this thesis was to optimize the conditions under which a 100 % cellulose material enzymatically decomposes. Waste textile and waste cellulose represent a large source of carbon that can be used in the production of value–added chemicals. The main goal of this diploma thesis was to test different conditions for the enzymatic decomposition of cellulose waste such as temperature range, enzymes concentration and different buffer composition. We started with the optimization of the temperature and tested how the reaction proceeds at three different temperatures (50, 55 and 60 °C). Here, the main goal was to check how the enzymatic mixture we used acts at these three different environments, thus how much will the material decompose. The results showed that the optimal temperature for the decomposition of cellulose is 50 °C. The second part of the diploma thesis evaluates if a higher concentration of enzymes would get better results regarding cellulose waste decomposition. The results here showed that an increased enzyme concentration does not improve the efficiency of the reaction under the tested conditions. Additionally, two different buffers 0.1 M NH4Cl and 0.1 M (NH4)2SO4 were tested as environments for the enzymatic degradation of cellulose waste. We got a higher glucose concentration in the reaction with (NH4)2SO4, as well as less variability of the pH, which led to a lower NaOH consumtion.
Keywords: enzymatic cellulose decomposition, optimization, temperature effect, NH4Cl, (NH4)2SO4, Cellic® CTec2
Published in DKUM: 13.09.2023; Views: 270; Downloads: 12
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