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Opis: Acetic acid bacteria (AAB) produce acetic acid but are also gaining importance as safe microorganisms for producing extracellular polysaccharides (EPSs). The best-known homopolysaccharides among them are cellulose and levan. In addition, acetic acid bacteria also produce heteropolysaccharides, water-soluble acetans. Isolates from the broth of organic and conventional apple cider vinegar production were screened for biofilm production. Phenotypic and genomic diversity of EPS-producing isolates was assessed. The diversity of phenotypically different EPSs of apple cider vinegar isolates was investigated at the gene level for the following novel strains: Komagataeibacter (K.) melomenusus SI3083, K. oboediens SI3053, K. pomaceti SI3133, and Gluconacetobacter (Ga.) entanii SI2084. Strain K. melomenusus SI3083 possesses cellulose operons bcs1, bcs2, and bcs4 together with the type I acetan cluster in the absence of the levan operon, strain K. oboediens SI3053 has the operons bcs1, bcs2, bcs3, and bcs4, the levan operon, and the acetan cluster (type I), and the strains K. pomaceti SI3133 and Ga. entanii SI2084 both contain recently described novel ace-type II cluster in addition to the incomplete operon bcs1. A comparison of the genetic diversity of these EPSs to those of the reference strains suggests that the studied EPSs are not species-descriptive. The results of this study deepen our understanding of the genetic variability of the EPS genes in AAB, thereby enabling us to better characterize and exploit the various insoluble and soluble exopolysaccharides produced by AAB for biotechnological applications in the future.
Ključne besede: acetic acid bacteria genomes, apple cider vinegar microbiota, biofilm production, bacterial cellulose, acetan, Acetobacter, Komagataeibacter
Objavljeno v DKUM: 26.09.2024; Ogledov: 0; Prenosov: 12
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Opis: The microbial production of cellulose using different bacterial species has been extensively examined for various industrial applications. However, the cost-effectiveness of all these biotechnological processes is strongly related to the culture medium for bacterial cellulose (BC) production. Herein, we examined a simple and modified procedure for preparing grape pomace (GP) hydrolysate, without enzymatic treatment, as a sole growth medium for BC production by acetic acid bacteria (AAB). The central composite design (CCD) was used to optimise the GP hydrolysate preparation toward the highest reducing sugar contents (10.4 g/L) and minimal phenolic contents (4.8 g/L). The experimental screening of 4 differently prepared hydrolysates and 20 AAB strains identified the recently described species Komagataeibacter melomenusus AV436T as the most efficient BC producer (up to 1.24 g/ L dry BC membrane), followed by Komagataeibacter xylinus LMG 1518 (up to 0.98 g/L dry BC membrane). The membranes were synthesized in only 4 days of bacteria culturing, 1 st day with shaking, followed by 3 days of static incubation. The produced BC membranes in GP-hydrolysates showed, in comparison to the membranes made in a complex RAE medium 34 % reduction of crystallinity index with the presence of diverse cellulose allomorphs, presence of GP-related components within the BC network responsible for the increase of hydrophobicity, the reduction of thermal stability and 48.75 %, 13.6 % and 43 % lower tensile strength, tensile modulus, and elongation, respectively. Here presented study is the first report on utilising a GP-hydrolysate without enzymatic treatment as a sole culture medium for efficient BC production by AAB, with recently described species Komagataeibacter melomenusus AV436T as the most efficient producer in this type of food-waste material. The scale-up protocol of the scheme presented here will be needed for the cost-optimisation of BC production at the industrial levels.
Ključne besede: grape pomace hydrolysate, bacterial cellulose, acetic acid bacteria, Komagataeibacter melomenusus
Objavljeno v DKUM: 26.07.2024; Ogledov: 98; Prenosov: 8
Celotno besedilo (8,06 MB)
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Opis: In this study, we explored the development of cationized 2-hydroxyethyl cellulose (HEC) and succinylated polyallylamine (PAA) in conjunction with polyvinyl alcohol (PVA) for potential applications as antimicrobial wound dressings. Quaternary ammonium compounds are known for their broad-spectrum antimicrobial properties against both Gram-negative and Gram-positive bacteria, but their non-selectivity can lead to high cytotoxicity. To improve the biocompatibility of the cationic materials investigates two distinct approaches. The first approach involves reducing the cationic nature of protonated PAA at a pH below 8.3 through amidation reaction with succinic anhydride. Gradual reduction of the cationic charge is achieved by varying the molar ratios of succinic anhydride during the reaction process. Notably, this reaction can be carried out in an aqueous solution, eliminating potential issues associated with solvent removal. The second part of this thesis focuses on introducing cationic charge by covalently binding naturally occurring quaternary ammonium compounds, such as betaine hydrochloride (BET HCl), choline chloride (ChCl), and carnitine hydrochloride (carnitine). Using 1,1′-carbonyldiimidazole (CDI), we quaternized HEC in anhydrous DMSO, with a detailed investigation of the reaction mechanism by isolating and characterizing intermediate products. This same procedure was applied to form a cationic dimer between BET HCl and ChCl. The chemical structures of the resulting materials were characterized using attenuated total reflectance infrared spectroscopy (ATR-IR) and nuclear magnetic resonance (NMR). The quantification of cationic and total charge was determined through polyelectrolyte and potentiometric titration, respectively. While succinylated PAA exhibited the anticipated biological properties associated with the reduction of cationic characteristics, the same behaviour was not observed for quaternized materials. High cytotoxicity and low antimicrobial properties in the derivatized HEC may be attributed to inadequate purification and the sensitivity of fibroblasts. We produced electrospun non-woven mats incorporating PVA and these derived materials using a single-needle electrospinning machine. The average diameter of the fibres was determined through scanning electron microscopy (SEM) images. Despite the cytotoxicity and the absence of significant antimicrobial properties in these materials, they exhibit potential as effective cationic flocculants for wastewater treatment. Further investigations are pending to address purification issues and make slight adjustments to the procedure to potentially scale up production. These materials still hold promise for applications in both biomedical and environmental chemistry.
Ključne besede: cellulose, quaternary ammonium compounds, antimicrobial, cytotoxicity, electrospinning
Objavljeno v DKUM: 11.07.2024; Ogledov: 127; Prenosov: 32
Celotno besedilo (16,36 MB)

Ključne besede: chitosan, cellulose nanofibrils, anion exchange membrane, direct alkaline alcohol fuel cells
Objavljeno v DKUM: 10.04.2024; Ogledov: 222; Prenosov: 16
Celotno besedilo (5,47 MB)
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Opis: 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.
Ključne besede: acetic acid bacteria, bacterial cellulose, sustainable production, agricultural waste, food waste, genetic engineering, synthetic biology, biomaterial, Komagataeibacter, Novacetimonas
Objavljeno v DKUM: 28.03.2024; Ogledov: 279; Prenosov: 42
Celotno besedilo (5,82 MB)
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