1. Genetic diversity of exopolysaccharides from acetic acid bacteria isolates originating from apple cider vinegarsTadeja Vajdič, 2022, original scientific article Abstract: 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.
Keywords: acetic acid bacteria genomes, apple cider vinegar microbiota, biofilm production, bacterial cellulose, acetan, Acetobacter, Komagataeibacter
Published in DKUM: 26.09.2024; Views: 0; Downloads: 13
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2. Production efficiency and properties of bacterial cellulose membranes in a novel grape pomace hydrolysate by Komagataeibacter melomenusus ▫$AV436^T$▫ and Komagataeibacter xylinus LMG 1518Selestina Gorgieva, Urška Jančič, Eva Cepec, Janja Trček, 2023, original scientific article Abstract: 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.
Keywords: grape pomace hydrolysate, bacterial cellulose, acetic acid bacteria, Komagataeibacter melomenusus
Published in DKUM: 26.07.2024; Views: 98; Downloads: 8
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3. From nature to lab : sustainable bacterial cellulose production and modification with synthetic biologyVid 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: 279; Downloads: 44
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4. GO-enabled bacterial cellulose membranes by multistep, in situ loading : effect of bacterial strain and loading pattern on nanocomposite propertiesTobiasz 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: 341; Downloads: 13
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