1. Use of a heating system to control the probiotic beverage production in batch bioreactorJožef Ritonja, Andreja Goršek, Darja Pečar, 2021, original scientific article Abstract: Fermentation is a crucial bioengineering process, existentially important for modern society.
The most commonly used production unit for this process is the batch bioreactor. Its main advantage
is unsophisticated construction, which unfortunately results in its incapability of controlling the
transient state of the fermentation process. Control of the fermentation can significantly improve
the quality of the product and the economy of the process; therefore, it is useful for bioreactors to
be equipped with a control system. Based on the experimental results, we used an optimization
method to identify a mathematical model that describes the impact of the bioreactor’s temperature
on the fermentation’s transient process. The obtained model was applied for the design and synthesis
of the closed-loop control system. Simulations and experiments confirmed the effectiveness of the
proposed control system. In this way, we can ensure the consistent quality of the produced probiotic
product, increase the amount of the product, and shorten the fermentation time. The original results
display the feasibility of the closed-loop control of the batch bioreactor’s fermentation process by
changing the temperature. So far, the process has been carried without a closed-loop control system.
The problem is current and has not yet been solved sufficiently. There are many attempts published;
one of the last shows the possibility of controlling the fermentation process by changing the oxygen
supply, which is more complex and expensive for realization than the solution from our study.
Keywords: probiotic bewerages, fermentation, modelling, identification, control implementation
Published in DKUM: 16.06.2025; Views: 0; Downloads: 0
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2. Environmental impact assessment of organic rankine cycle using waste heat from the aluminium industryMonika Dokl, Gaja Strajnar, Annamaria Vujanović, Jan Puhar, Zdravko Kravanja, Lidija Čuček, 2025, original scientific article Abstract: Waste heat recovery technologies play an important role in enhancing energy efficiency and supporting sustainable energy production. This study investigates the utilization of waste heat from aluminium production through an Organic Rankine Cycle (ORC) system to generate electricity and heat simultaneously. Based on operational data from an aluminium plant, the system is firstly optimized from both the thermodynamic and economic perspectives. To maximize performance and to identify optimal configurations, a mathematical model is developed and solved using GAMS, capturing the complex interdependencies between the operational, economic and thermodynamic parameters. The environmental impact of the optimized scenarios is subsequently evaluated using a Life Cycle Assessment (LCA), considering a broad range of impact categories. The results indicate a maximum power output of 830.9 kW and a maximum net present value (NPV) of 51.71 M€, confirming the system’s technical and economic viability. The environmental assessment demonstrates the potential of ORC systems as sustainable energy solutions, with significant environmental unburdening under optimized operating conditions (up to -606.0 kg CO2 eq./h). A sensitivity analysis indicates that the greatest environmental benefits occur under the optimal thermodynamic scenario, achieved through the utilization of higher-energy flue gas streams (up to -515.0 kg CO2 eq./h), and under the optimal economic scenario by balancing the electricity and heat prices optimally for simultaneous heat and power production (up to -696.7 kg CO2 eq./h). These findings highlight the importance of the thermal input quality and availability in maximizing ORC performance. With the ability to prioritize electricity, heat, or both, the optimized ORC systems support flexible energy solutions tailored to specific applications and environmental conditions, offering a promising pathway for unburdening the environment through the efficient utilization of industrial waste heat.
Keywords: waste heat recovery, aluminium production, organic rankine cycle, environmental impact, life cycle assessment, sustainable energy solutions
Published in DKUM: 13.06.2025; Views: 0; Downloads: 5
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3. Water flow decrease of track-etched polyethylene terephthalate membranesAna Ambrož, Zhen Yao, Christopher Rojas, Polina Angelova, Armin Gölzhäuser, Irena Petrinić, 2025, original scientific article Abstract: Track-etched polyethylene terephthalate (TE-PET) membranes, characterized by their well-defined cylindrical pores and narrow pore size distribution, offer advantages in filtration applications but demonstrate a gradual decrease of water flux over time. In this work, we evaluate the performance of track-etched polyethylene terephthalate (TE-PET) membranes as microfilters in low-pressure cross-flow and dead-end filtration systems. Membranes with pore sizes between 0.2 and 2.5 μm and porosities of 0.2–20% were tested at different low pressures (0.02–10 bar). Monitoring water flux over time exhibited a significant reduction. This behaviour is attributed to polymer swelling within the pore walls due to the formation of a sol-gel film. Notably, this swelling is enhanced under dynamic flow conditions, with larger pores exhibiting more rapid and pronounced flux decline. When filtering organic solvents, the flux drop is less pronounced and depends on their viscosity and polarity. Surface characterization by atomic force microscopy further confirmed morphological changes in TE-PET support after water filtration. Additional contributing factors, such as fouling and compaction, are also discussed.
Keywords: track-etched support, polyethylene terephthalate, water filtration, swelling, sol-gel film, carbon nanomembrane
Published in DKUM: 13.06.2025; Views: 0; Downloads: 1
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4. Globoko evtektična topila za učinkovito in trajnostno ekstrakcijo bioaktivnih učinkovin iz olupkov izbranih slovenskih sort jabolk : magistrsko deloNika Marija Murenc, 2025, master's thesis Abstract: Bioaktivne učinkovine so sekundarni metaboliti, ki jih najdemo v različnih rastlinskih vrstah, tudi v sadju. Zaradi svojih bioloških lastnosti imajo lahko različne zdravilne učinke za človeka, zato se priporoča njihovo uživanje. Vir teh učinkovin niso le užitni deli sadja, temveč tudi stranski proizvodi, ki nastanejo kot zavržki pri njegovi predelavi. Med najbolj pogosto gojeno sadje na svetu spada jabolko, ki ima zaradi svoje predelave v različne izdelke tudi veliko različnih stranskih proizvodov oz. odpadkov. V magistrskem delu smo določali sestavo olupkov različnih slovenskih sort jabolk, pri čemer smo za ekstrakcijo bioaktivnih učinkovin iz njih, uporabili različna ekstrakcijska topila. V želji, da se najpogosteje uporabljena konvencionalna organska topila nadomesti z zelenimi alternativami, smo kot ekstrakcijska topila uporabili pet različnih globoko evtektičnih topil, njihove ekstrakte pa smo primerjali z ekstrakti, pridobljenimi s 56 % etanolom. V globoko evtektičnih topilih smo kot akceptorja vodikovih vezi uporabili holin klorid ali mentol, kot donorje vodikovih vezi pa 1,2-propandiol, ocetno kislino, mlečno kislino in levulinsko kislino. V posameznih ekstraktih smo kvantificirali izbrane spojine in določali uspešnost posameznih topil, poleg tega pa smo določali tudi antioksidativno učinkovitost posameznih ekstraktov jabolčnih olupkov z različnimi antioksidativnimi testi (ABTS, FRAP, DPPH, TPC). Rezultati magistrskega dela so pokazali, da so globoko evtektična topila učinkovita in okolju prijazna alternativa etanolu pri ekstrakciji fenolnih spojin iz jabolčnih olupkov. Antioksidativni testi so potrdili, da ekstrakti, pridobljeni s takimi topili, pogosto dosegajo enako ali boljšo aktivnost kot etanolni ekstrakti.
Keywords: globoko evtektično topilo, ekstrakcija, bioaktivne učinkovine, antioksidanti, jabolčni olupki
Published in DKUM: 02.06.2025; Views: 0; Downloads: 9
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5. 3D-printed cellulose aerogels minimally cross-linked with polyurea : a robust strategy for tissue engineeringAna Iglesias-Mejuto, Grigorios Raptopoulos, Nanthilde Malandain, Mariana Neves Amaral, Inés Ardao Palacios, Matjaž Finšgar, Anna Laromaine, Anna Roig, Catarina Pinto Reis, Carlos A. García-González, Patrina Paraskevopoulou, 2025, original scientific article Abstract: Cellulose and its derivatives are increasingly explored in biomedical applications due to their biocompatibility,biodegradability, and mechanical performance. In regenerative medicine, aerogel scaffolds with tunable morphology and compositionare highly valued for their ability to support tissue regeneration. Three-dimensional (3D) printing offers an effective method tofabricate aerogels with hierarchical pore structures, comprising interconnected macropores and mesopores, that are crucial for tissueengineering. For clinical use, 3D printing should ensure the structural integrity of printed structures and achieve a printing resolutionthat allows for customization. In this work, the X-aerogel technology, implemented via polyurea cross-linking, was applied to 3D-printed cellulose structures, thereby expanding the potential applications of both technologies. Specifically, 3D-printedmethylcellulose (MC) and MC doped with bacterial cellulose nanofiber (MCBCf) gels were cross-linked with an aliphaticpolyurea, yielding, after supercritical drying, the corresponding (X-MC and X-MCBCf) aerogels. Elaborate characterization withATR-FTIR, XPS, ToF-SIMS, N2 porosimetry, He pycnometry, and SEM confirmed the formation of polyurea on the biopolymerframework, reinforcing the structure and improving the mechanical properties without altering the morphology or texturalcharacteristics of the materials. A significant outcome of cross-linking with polyurea is the long-term stability of X-MC and X-MCBCf aerogels in water, in contrast to their native counterparts, and their capacity to absorb water up to 1800% w/w within only 2h. Preliminary biological evaluation of the materials, including in vitro (cell compatibility, hemolytic activity), in ovo (HET-CAM),and in vivo (A. salina model) tests, showed good cell viability, blood compatibility, and safety for living organisms. From afundamental materials perspective, the most important finding of this work is the disproportionally high stability of X-MC and X-MCBCf in physiological environments, achieved with only a minimal (almost undetectable) amount of cross-linking polyurea. Froman application standpoint, the findings of this study, collectively, position these aerogels as sustainable and promising candidates fortissue engineering scaffolds.
Keywords: 3D printing, aerogels, cellulose, methylcellulose, polyurea, tissue engineering, X-aerogels
Published in DKUM: 30.05.2025; Views: 0; Downloads: 3
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6. Spatiotemporal analysis and physicochemical profiling of ▫$PM_10$▫ and ▫$PM_2.5$ ▫ in SloveniaMaja Ivanovski, Ivan Anžel, Darko Goričanec, Danijela Urbancl, 2025, original scientific article Abstract: Particulate matter (PM10 and PM2.5) is a key contributor to urban air pollution and poses significant health risks, particularly in densely populated areas. While conventional air quality monitoring focuses on particle size and concentration, this study emphasizes the importance of understanding chemical composition and emission sources for effective air pollution management. PM samples were collected between 2019 and 2022 at two locations in the Republic of Slovenia: a traffic-dominated urban site and an industrial area. Annual average PM10 concentrations ranged from 14 to 34 μg/m3, and those of PM2.5 ranged from 9 to 22 μg/m3. In addition to decreasing annual concentrations, a notable reduction in exceedance days was observed between 2019 and 2022, indicating the effectiveness of recent air quality improvement measures. Meteorological data and statistical models were used to assess environmental influences on PM variability. Advanced SEM-EDS analysis revealed substantial seasonal and spatial differences in particle composition, with key elements such as silicon (4.3–28.4%), carbon (13.1–61.7%), and trace amounts of lead and zinc varying across sites and particle types. Mineral dust (Si, Al, Ca, Fe, Mg), originating from soil resuspension, construction, and Saharan dust, was dominant. Combustion-related particles containing C, Pb, Zn, and Fe oxides were associated with vehicle emissions, industrial processes, and biomass burning. Secondary aerosols, such as sulphates and nitrates, showed seasonal trends, with higher concentrations in summer and winter, respectively. The results confirm that PM levels are driven by complex interactions between local emissions, weather conditions, and seasonal dynamics. The study supports targeted policy measures, particularly regarding residential heating and traffic emissions, to improve air quality.
Keywords: air pollution, air quality, PM particles, SEM-EDS, Slovenia
Published in DKUM: 30.05.2025; Views: 0; Downloads: 1
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7. Surface and subsurface mass spectrometric analysis of dexamethasone in solid pharmaceutical dosage formsMatjaž Finšgar, 2025, original scientific article Abstract: This study presents an in-depth mass spectrometric investigation of dexamethasone (DEX) distribution within pharmaceutical tablets using time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with gas cluster ion beam (GCIB) sputtering. Fragmentation mechanism of DEX was identified, which enabled the determination of three-dimensional chemical imaging of the active ingredient in both surface and subsurface regions. The data reveal that a 4-mg DEX formulation exhibits a continuous and extended distribution of the drug into the tablet matrix, while a 0.5-mg formulation shows DEX localized in distinct, isolated domains. Topographical features and the overall composition of the surface were confirmed by complementary analyses employing atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). These results demonstrate how molecule distribution patterns can be linked to formulation heterogeneity using advanced mass spectrometric techniques, opening new possibilities for pharmaceutical manufacturing quality control and optimization.
Keywords: mass spectrometry, dexamethasone, pharmaceutical tablets, DEX, ToF-SIMS
Published in DKUM: 30.05.2025; Views: 0; Downloads: 0
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8. Macroscale superlubricity with a high load-carrying capacity enabled by nitrogen-doped graphene quantum dots in lubricated silicon-doped amorphous carbon filmsIrfan Nadeem, Matjaž Finšgar, Goran Dražić, Bojan Ambrožič, Matjaž Malok, Albano Cavaleiro, Mitjan Kalin, 2025, original scientific article Abstract: Achieving macroscale superlubricity with engineering materials is highly desirable for energy conservation, environmental benefits, and longevity of mechanical components. However, attaining superlubricity in aqueous-lubricated systems with enhanced load-bearing capacity remains challenging in metallic materials. Herein, nitrogen-doped graphene quantum dots (NGQDs) as a nano-additive in aqueous glycerol facilitate macroscale superlubricity between friction pairs of steel and silicon-doped hydrogenated amorphous carbon (a-C:H:Si). Superlubricity is observed in boundary-lubrication regime with a friction coefficient of 0.0055–0.0097 under various sliding conditions. Notably, the wear of the steel counterface (k = 8.51 × 10−9 mm3/Nm) decreased by 47.8%, resulting in a final contact pressure of 206.7 MPa, which exceeds values reported for aqueous-lubricated systems during superlubricity. The lubrication mechanism reveals that NGQDs' adsorption on the steel-worn surface, coupled with the tribocatalytic generation of FeNxCy moieties on a-C:H:Si surface, is crucial for reducing friction. These FeNxCy moieties, with a multitude of active sites, facilitate the subsequent anionic adsorption of pyrrolic-rich NGQDs. Simultaneously, the formation of amorphous graphitic film, driven by continuous shearing and exfoliation of graphene sheets within the adsorbed NGQDs, contributes to the stability of superlubricity. These findings provide insights into the functional characteristics of NGQDs for achieving superlubricity in aqueous-lubricated systems, paving the way for future energy-saving applications.
Keywords: macroscale superlubricity, metallic materials, streel
Published in DKUM: 29.05.2025; Views: 0; Downloads: 1
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9. Zwitterionic, ion-in-conjugation porous polymer networks : synthesis and photooxidation of bisphenol A in waterAleksander Saša Markovič, Tomaž Kotnik, Sebastijan Kovačič, 2025, original scientific article Abstract: In this work, we have developed an easy approach for vinylene-linked ion-in-conjugation porous polymer networks (IIC-PPN) using Knoevenagel polycondensation of predesigned zwitterionic N-(3-sulfopropyl)-2,6-(dimethyl)pyridinium salt and 1,3,5-triformylbenzene as monomers. The resulting IIC-PPNs exhibit a porous morphology with high specific surface areas up to 263 m2·g-1. Although the IIC-PPN network contains arylene-vinylene nodes that make it apolar, the incorporation of zwitterionic pyridinium building blocks enable a significant ionic dipole, which is reflected in the water uptake of 14.5 g·g-1, which is higher than that of similar poly(arylene-cyano-vinylene)s with 7.0, 8.5 and 5.3 g·g-1 for PAV–CN, PAV–OMe, and PAV–CHO, respectively. The IIC-PPNs exhibit significant semiconducting properties with optical absorption band edges of 512 nm and an electrochemical band gap of 2.55 eV. The intriguing properties of IIC-PPN prompted us to use them as heterogeneous photocatalysts to photooxidize the endocrine disrupting compound bisphenol A (BPA) dissolved in water under visible light.
Keywords: conjugated polymers, zwitterion, Ion-in-conjugation, IIC, heterogeneous photocatalysis, bisphenol A, BPA
Published in DKUM: 29.05.2025; Views: 0; Downloads: 0
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10. New approach for adsorptive removal of the antibiotic ciprofloxacin: carboxymethyl-dextran-functionalised magnetic iron oxide nanomaterialsErik Mihelič, Lidija Fras Zemljič, Marjana Simonič, Sašo Gyergyek, Alenka Vesel, Silvo Hribernik, Matej Bračič, Ivan Anžel, Olivija Plohl, 2025, original scientific article Abstract: Antibiotic residues in environmental media pose a significant health, social and economic problem and require effective removal strategies. This study presents a novel approach for the removal of the antibiotic ciprofloxacin from water sources using magnetic iron oxide nanoparticles (MNPs) synthesised by co-precipitation, and subsequently functionalised with the polysaccharide carboxymethyl-dextran (CMD). The prepared nanoadsorbent was characterised extensively by various physicochemical analyses, to evaluate its morphology, crystal structure, surface chemistry, electrokinetic properties, thermogravimetric properties and magnetic features. These analyses confirmed the successful functionalisation of the MNPs with CMD highlighting its potential for effective adsorption applications. The stability of CMD coating on MNPs was evaluated in terms of total carbon content, an important, yet often overlooked factor. The adsorption performance of MNPs@CMD for ciprofloxacin was investigated systematically by studying the effects of adsorbent dosage, pH, initial ciprofloxacin concentration, ionic strength, adsorption time and kinetics, temperature, and reusability. Under optimal conditions, nanoadsorbent exhibited a satisfactory maximum adsorption capacity of 14.71 mg/g, and maintained a removal eff iciency of 79 % after four cycles, with minimal desorption of CMD layer on the MNPs. These findings demonstrate the potential of this magnetic polysaccharide nanoadsorbent for effective removal of ciprofloxacin from aqueous environments, enabling magnetic recovery and reuse.
Keywords: Carboxymethyl-dextran-MNPs, ciprofloxacin, adsorption
Published in DKUM: 26.05.2025; Views: 0; Downloads: 6
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