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2.
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: 120; Downloads: 12
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3.
Study on commercially available membranes for alkaline direct ethanol fuel cells
Michaela Roschger, Sigrid Wolf, Andreas Billiani, Kurt Mayer, Maša Hren, Selestina Gorgieva, Boštjan Genorio, Viktor Hacker, 2023, original scientific article

Abstract: This study provides a comparison of different commercially available low-cost anion exchange membranes (AEMs), a microporous separator, a cation exchange membrane (CEM), and an anionic-treated CEM for their application in the liquid-feed alkaline direct ethanol fuel cell (ADEFC). Moreover, the effect on performance was evaluated taking two different modes of operation for the ADEFC, with AEM or CEM, into consideration. The membranes were compared with respect to their physical and chemical properties, such as thermal and chemical stability, ion-exchange capacity, ionic conductivity, and ethanol permeability. The influence of these factors on performance and resistance was determined by means of polarization curve and electrochemical impedance spectra (EIS) measurements in the ADEFC. In addition, the influence of two different commercial ionomers on the structure and transport properties of the catalyst layer and on the performance were analyzed with scanning electron microscopy, single cell tests, and EIS. The applicability barriers of the membranes were pointed out, and the ideal combinations of membrane and ionomer for the liquid-feed ADEFC achieved power densities of approximately 80 mW cm–2 at 80 °C.
Keywords: bioethanol, electrodes, fluoropolymers, ionomers, membranes
Published in DKUM: 26.03.2024; Views: 90; Downloads: 7
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4.
Funkcionalizacija tekstilij z izoliranimi gradniki jajčnih lupin in izdelava nanovlaken iz le - teh : magistrsko delo
Rosvita Pliberšek, 2024, master's thesis

Abstract: Glavna tema magistrske naloge je izolacija gradnikov jajčnih lupin kokoši in prepelice ter obdelava sintetičnih (poliester, PES) ter naravnih (bombaž) tekstilij z le-tem. Izbira teme je temeljila na pogledu na jajčne lupine kot odpadek in hkrati kot uporabno surovino, ki lahko izboljša lastnosti drugih surovin oz. materialov, pri tem pa lahko ustvarimo napredek na področju ognjevarnih, medicinskih ter UV-zaščitnih oblačil. V nalogi smo preverjali izbrane funkcionalne lastnosti vodne raztopine jajčnih lupin, kot so: velikosti delcev in zeta potencial, pH vrednost, motnost, površinska napetost, stični kot, električna prevodnost in antioksidativnost; ter analizirali učinkovitost obdelave poliestrnih (PES) in bombažnih tkanin s pridobljenimi raztopinami, pri čemer smo uporabili napredne preparativne (hidrotermična razgradnja- hidroliza) in analitske metode (merjenje pH, spektroskopija). Ugotovili smo, da je vzorec v obliki vodne raztopine pokazal dobre lastnosti na področju površinske lastnosti, prav tako je pokazalo dobre rezultate pri meritvah zeta potenciala ter pri merjenju električne prevodnosti. Pri obdelanih PES in bombažnih vzorcih s to raztopino jajčnih lupin, pa lahko poudarim, da so bili vidni rezultati na področju ognjevarnosti, protimikrobnosti in UZF. Rezultati sicer niso bili izraziti, ampak bili opazni in so mejili v dobro smer.
Keywords: jajčne lupine, hidroliza, funkcionalizacija, izolirani gradniki, PES in bombažne tekstilije, ognjevarnost, medicinske tekstilije, UV zaščita
Published in DKUM: 22.03.2024; Views: 158; Downloads: 12
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5.
Dopamine-assisted modification of polypropylene film to attain hydrophilic mineral-rich surfaces
Alenka Ojstršek, Angela Chemelli, Azra Osmić, Selestina Gorgieva, 2023, original scientific article

Abstract: The presented study focuses on the modification of polypropylene (PP) film with tetraethyl orthosilicate (TEOS) under heterogeneous conditions via polydopamine/polyethylene imine (PDA/PEI) chemistry using a facile dip-coating procedure to attain hydrophilic mineral-rich surfaces. Thus, the resulting PP-based films were further immersed in ion-rich simulated body fluid (SBF) to deposit Ca-based minerals onto the film’s surfaces efficiently. In addition, the chemical reaction mechanism on PP film was proposed, and mineralisation potential inspected by determination of functional groups of deposits, zeta potential, hydrophilicity and surface morphology/topography using Fourier transform infrared (FTIR) spectroscopy, streaming potential, water contact angle (WCA), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The obtained results show the improved wettability of samples on account of PDA inclusion (WCA was reduced from 103° for pure PP film to 28° for PDA-modified film), as well as the presence of functional groups, due to the PDA/PEI/TEOS surface functionalisation, increased the ability of minerals to nucleate on the PP film’s surface when it was exposed to an SBF medium. Moreover, the higher surface roughness due to the silica coatings influenced the enhanced anchoring and attachment of calcium phosphate (CaP), revealing the potential of such a facile approach to modify the chemically inert PP films, being of particular interest in different fields, including regenerative medicine.
Keywords: polypropylene film, dopamine-assisted modification, hydrophilicity, mineralization
Published in DKUM: 15.03.2024; Views: 170; Downloads: 2
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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: 171; Downloads: 7
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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: 156; Downloads: 9
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8.
Razvoj celulozno-pektinskih membran za adsorpcijo kationskih barvil iz modelnih raztopin : magistrsko delo
Maja Mazej, 2023, master's thesis

Abstract: Vse večja rast prebivalstva in razvoj industrije sta močno vplivala na povečano porabo vode. Velik problem pri tem pa predstavljajo predvsem obarvane odpadne vode v tekstilni industriji, ki so zelo obremenjene in predstavljajo ob izpustu veliko obremenitev za okolje. Odstranjevanje barvil iz odpadnih vod, zaradi kompleksnih molekulskih struktur predstavlja velike izzive industriji. Tako so želje po ponovni uporabi spodbudile razvoj novih tehnologij, ki bi na učinkovit in cenovno ugoden način te vode pred izpustom v vodotok tudi ustrezno prečistile. Že predhodne raziskave so pokazale, da je ena izmed učinkovitejših fizikalnih metod ločevanja barvil membranska adsorpcija. Magistrsko delo predstavlja preučitev različnih možnosti in načinov, s katerimi bi uspešno ločili kationska barvila iz modelnih odpadnih vod z uporabo membranskih adsorbentov na osnovi celuloznih nanofibrilov in pektina. Cilj magistrskega dela je bil sinteza cenovno – učinkovitih, okolju prijaznih membran, na osnovi nanofibrilirane celuloze in pektina, na osnovi enostavnih postopkov mešanja, vlivanja in sušenja z dodatkom citronske kisline (CA) in CaCl2 kot zamreževalca. Različne strukturirane membrane smo primarno okarakterizirali glede na njihove morfološke in fizikalno-kemijske lastnosti, ter sekundarno glede na njihove adsorpcijske lastnosti, na podlagi katerih smo preučili mehanizme in učinkovitost adsorpcije. Pri tem smo pridobili membrane, ki bi lahko uspešno vplivale na ločitev kationskih barvil iz vodnih medijev. Gravimetrična analiza membran nam je podala zaključek, da so vse membrane na osnovi mešanic primarnih surovin brez dodanih zamreževalcev neobstojne v vodi, zato je dodatek zamreževalcev ključnega pomena. Opazili smo, da membrana formirana le iz CNFjev, ne potrebuje zamreževalca, saj je samostojno obstojna v vodi, kar pa gre pripisati intenzivnemu in ireverzibilnemu povezovanju nanofibrilov pri procesu sušenja, v odsotnosti drugih komponent. Z ATR – FTIR spektroskopijo smo ugotovili, da obe vrsti zamreževalca, tako CA kot CaCl2, naredita spremembo v kemijski strukturi, in prispevata k določeni meri stabilizacije in s tem nakazujeta na uspešno ionsko (CaCl2), ter kovalentno (CA) vezavo. Z rezultati, pridobljenimi pri potenciometrični titraciji, smo ugotovilii, da dosežejo največji skupni naboj tiste membrane, ki vsebujejo zamreževalec CA. K doseganju največjega naboja membrane je prispevala predvsem prisotnost karboksilnih skupin, ki tudi vplivajo na večjo adsorpcijsko sposobnost membran. Izmerjene vrednosti z goniometrijo pri vseh membranah so bile nižje od 90° in kažejo na izrazito hidrofilnost membran, saj osnovne komponente vsebujejo hidrofilne hidroksilne, ter karboksilne skupine. Z optično mikroskopijo smo membrane le makroskopsko opazovali in zaključili, da imajo membrane izotropne strukture, brez preferenčne ureditve. Z rezultati gravimetričnega določanja % nabrekanja smo ugotovili, da zamreževalec pozitivno vpliva na ohranjanje strukture membrane v vodi. Pektin pa očitno vpliva na nestabilnost (karboksilne skupine, ob stiku z vodo dezintegrirajo), če primerjamo membrane z dodanim pektinom in membrano 10, ki ima vključen samo CNF. Z analizo adsorpcije barvil (UV-VIS spektrokoskopija) vidimo uspešno adsorpcijo obeh barvil Basic Yellow 28 kot tudi Basic Blue 22 v različnih koncentracijah na membrane. Najbolj uspešen primer navzemanja barvila je v primeru CNF/PC membran, ker ima pektin naboj, ki omogoča uspešno vezavo barvila. Dokazali smo tudi uspešno navzemanje barvila na membrane, pri obeh vrstah barvila. Odstotek razbarvanja kopeli se razlikuje glede na koncentracije v primeru najnižje koncentracije in najmanjše razbarvanje v primeru najvišje koncentracije, kar velja za vse membrane. Adsorpcija barvil je pogojena s kemijsko strukturo ter mikrostrukturo membrane, ki se uporabi kot adsorbent.
Keywords: Celulozni nanofibrili, pektin, zamrežanje, membrana, membranska adsorpcija, kationska barvila
Published in DKUM: 09.02.2023; Views: 542; Downloads: 64
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9.
Ekologija plemenitilnih procesov : navodila za vaje
Darinka Fakin, Selestina Gorgieva, Alenka Ojstršek, 2022

Abstract: Poseben problem odpadkov v tekstilni industriji predstavljajo odpadne tehnološke vode, predvsem tiste, ki nastajajo pri plemenitenju tekstilij. Te odpadne vode so močno obremenjene, vsebujejo različne kemikalije in tekstilna pomožna sredstva, imajo ekstremne pH-vrednosti in visoke KPK in BPK vrednosti, različne tipe organskih barvil, kar povzroča obarvanost, vsebujejo fosfate, sulfate in ostale soli, tenzide, maščobe in olja ter različne tipe težkih kovin. Tekstilne odpadne vode so zelo heterogene po sestavi, zato je čiščenje takšnih voda kompleksna naloga, za katero ni idealne in v naprej izdelane metode. Glede na proizvodni proces je potrebno izbrati fleksibilno in ekonomsko upravičeno tehnologijo čiščenja. Pri izbiri tehnologije čiščenja odpadnih voda moramo upoštevati njihovo količino in kakovost, ki jo ovrednotimo s specifičnimi in sumarnimi ekološkimi parametri.
Keywords: tekstilna odpadna voda, plemenitenje, čiščenje odpadnih vod, ekološki parametri
Published in DKUM: 15.11.2022; Views: 542; Downloads: 25
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10.
Oblikovanje kompozitnih membran na osnovi hitozana s funkcionalizirano nanofibrilirano celulozo za uporabo v gorivnih celicah : doktorska disertacija
Maša Hren, 2022, doctoral dissertation

Abstract: Gorivne celice so obetavne naprave za neposredno pretvorbo kemijske energije v električno s potencialno aplikacijo na številnih področjih, vendar komercializacijo trenutno najbolj razvitih vodikovih gorivnih celic ovira visok strošek nekaterih komponent, kot so katalizatorji na osnovi platine. Kot ekonomsko bolj ustrezna alternativa se razvijajo alkalne gorivne celice (AAEMFC), ki kot trdni polielektrolit med elektrodama uporabljajo anionsko izmenjevalno membrano (AEM). Trenutne komercialno razpoložljive AEM, so drage in osnovane na sintetičnih polimerih, njihova priprava pa je navadno kompleksna in okolju neprijazna, kar nakazuje na potrebo po razvoju novih visoko učinkovitih, preprostih za pripravo, okolju prijaznih in ekonomsko sprejemljivih AEM. Doktorska disertacija se osredotoča na razvoj novih biopolimernih AEM na osnovi hitozana (CS) z organskimi vključki nanofibrilirane celuloze (CNF), funkcionalizirane CNF (CNF(D) in CNF(P)) in anorganskega N-dopiranega grafenovega oksida (N-GO). Funkcionalizacijo CNF z namenom uvedbe pozitivnega naboja, ki ga prispevajo kvaterne dušikove skupine, smo izvedli z uporabo organosilanskega reagenta DMAOP in polikationskega reagenta PDDA ter dobljene produkte CNF(D) in CNF(P), uporabne kot vključke, analizirali z metodami ATR-FTIR, 13C NMR in 29Si spektroskopijo, FE-SEM, TGA, DSC analizo, meritvami zeta potenciala in s polielektrolitsko titracijo, ter jih vključili v CS membrane. Za izbiro najobetavnejših AEM za vključitev v AAEMFC smo uporabili eksperimentalni načrt in pripravili serije CS membran s posameznimi vključki, ki smo jih okarakterizirali glede na ionsko prevodnost, kapaciteto ionske izmenjave, prehajanje goriva, navzemanje alkalije in nabrekanje, ter jih analizirali z metodami ATR-FTIR, SEM, TGA, XRD in določili mehanske lastnosti. S celičnim testom najobetavnejših AEM v AAEMFC smo ugotovili, da imajo pripravljene CS membrane z vključki N-GO (Pmax = 149 mW cm-2), CNF (Pmax = 62 mW cm-2), CNF(P) (Pmax = 62 mW cm-2) ter kombiniranima CNF in CNF(P) (Pmax = 65 mW cm-2) višje Pmax, kot komercialna membrana Fumatech (Pmax = 35 mW cm-2), s čimer smo identificirali njihov potencial za uporabo v AAEMFC.
Keywords: alkalna gorivna celica, anionsko izmenjevalna membrana, hitozan, vključki, nanofibrilirana celuloza, grafenov oksid
Published in DKUM: 10.11.2022; Views: 597; Downloads: 112
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