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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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Abstract: Consumers’ preference towards healthy and novel foods dictates the production of organic unfiltered bottled vinegar that still contains acetic acid bacteria. After ingesting vinegar, the bacteria come into close contact with the human microbiota, creating the possibility of horizontal gene transfer, including genetic determinants for antibiotic resistance. Due to the global spread of antimicrobial resistance (AMR), we analyzed the AMR of Acetobacter and Komagataeibacter species originating mainly from vinegars. Six antibiotics from different structural groups and mechanisms of action were selected for testing. The AMR was assessed with the disk diffusion method using various growth media. Although the number of resistant strains differed among the growth media, 97.4%, 74.4%, 56.4%, and 33.3% of strains were resistant to trimethoprim, erythromycin, ciprofloxacin, and chloramphenicol, respectively, on all three media. Moreover, 17.9% and 53.8% of all strains were resistant to four and three antibiotics of different antimicrobial classes, respectively. We then looked for antimicrobial resistance genes in the genome sequences of the reference strains. The most common genetic determinant potentially involved in AMR encodes an efflux pump. Since these genes pass through the gastrointestinal tract and may be transferred to human microbiota, further experiments are needed to analyze the probability of this scenario in more detail.
Keywords: acetic acid bacteria, Acetobacter, Komagataeibacter, antimicrobial resistance, trimethoprim resistance, erythromycin resistance, ciprofloxacin resistance, chloramphenicol resistance, ampicillin resistance, gentamicin resistance
Published in DKUM: 24.08.2023; Views: 479; Downloads: 53
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Abstract: Avtor v prispevku predstavlja različne teorije o alternativnih insolvenčnih postopkih, ki bi teoretično lahko nadomestili ali vsaj dopolnili trenutni sistem korporacijskega insolvenčnega prava, ki pozna predvsem stečajni postopek in postopek finančne reorganizacije. Avtor v uvodnem poglavju izpostavi, da odločitev o tem, ali naj se nad družbo uvede stečaj ali finančna reorganizacija, temelji na odgovoru na vprašanje, ali je podjetje dolžnika ekonomsko učinkovito ali ne. V skladu s splošno sprejeto ekonomsko teorijo naj se namreč finančno reorganizirajo zgolj ekonomsko učinkovita podjetja. Ugotavljanje ekonomske (ne)učinkovitosti se v praksi izkaže za zapleteno, relativno nezanesljivo in pogosto zelo drago. Hkrati v teoriji ni jasno, kdo naj prevzame breme odločitve o tem vprašanju in kakšen naj bo postopek tega odločanja. Posledično so številni teoretiki nezadovoljni s trenutnim sistemom insolvenčnega prava in predlagajo različne alternative, ki jih v grobem lahko razdelimo na sisteme javnih dražb, modele avtomatizma in modele, ki temeljijo na ex ante pogodbenih dogovorih. Avtor v zaključku izpostavi, da čeprav poteka razprava o alternativnih sistemih že dobrih 30 let, ti predlogi v veliki večini v praksi nikoli niso zaživeli.
Keywords: Slovenija, pravo, insolventnost, zakonodaja, insolvenčno pravo, stečaj, finančna reorganizacija, ekonomska analiza prava
Published in DKUM: 02.08.2018; Views: 1009; Downloads: 121
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Abstract: Avtorja v prispevku predstavita temeljno ekonomsko teorijo financiranja visokega šolstva, torej prikaz različnih možnosti, ki jih ima država na voljo, ko postavlja oz. spreminja svoj model financiranja. Avtorja definirata temeljne zahteve, ki morajo biti spoštovane pri oblikovanju sistema financiranja, in sicer: zadostnost, učinkovitost in pravičnost ter predstavita temeljne razloge za javno in zasebno financiranje visokega šolstva. Prispevek zaključuje predstavitev različnih modelov alokacije javnih sredstev, katerih izbira je odvisna od ciljev, ki jih z javnim financiranjem želimo zasledovati.
Keywords: Slovenija, visoko šolstvo, financiranje, zakonodaja, financiranje visokega šolstva, zadostnost, učinkovitost in pravičnost, javno financiranje, zasebno financiranje
Published in DKUM: 01.08.2018; Views: 914; Downloads: 64
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Abstract: Diplomsko delo obravnava zunanjo in notranjo oblikovanje nemških prestižnih in ne prestižnih avtomobilskih znamk točno določenih modelov. Na začetku je predstavljen razvoj avtomobila in kako je prišlo do oblikovanja avtomobila, kot ga poznamo danes. Skozi leta, ko se je razvijalo oblikovanje, so se tudi razvijali različni stili oblikovanja, ki so prav tako predstavljeni. Osrednji del diplomske naloge obravnava predstavitev zunanjega in notranjega oblikovanja sodobnih prestižnih in ne prestižnih izbranih modelov nemških avtomobilov. Med sodobne prestižne nemške avtomobilske znamke prištevamo Audi, BMW, Porsche in Mercedes-Benz. Pri izbranih modelih prestižnih nemških avtomobilov sem izbrala Audi A4, BMW 3, Porsche Panamera in Mercedes-Benz C-razred. Med sodobne ne prestižne nemške avtomobile pa prištevamo Volkswagen ter Opel, kjer sem izbrala Volkswagen Passat in Opel Insignia za nadaljnjo obravnavo.
Keywords: postopek oblikovanja avtomobilov, zunanje oblikovanje nemških avtomobilov, notranje oblikovanje nemških avtomobilov, Audi, BMW, Porsche, Mercedes-Benz, Volkswagen, Opel
Published in DKUM: 21.09.2016; Views: 1166; Downloads: 114
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