1. Optimization of the supercritical extraction and decarboxylation process of industrial hempTaja Žitek Makoter, Petra Kotnik, Teo Makoter, Željko Knez, Maša Knez Marevci, 2025, izvirni znanstveni članek Opis: Cannabinoids are the main active ingredients of Cannabis sativa L., obtained by a suitable extraction method and decarboxylation, in which the acid forms of the cannabinoids are converted into active forms. Supercritical CO2 extraction method and decarboxylation process were optimized for 7 cannabinoids (CBD, CBDA, THC, THCA, CBGA, CBN and CBC). The optimal extraction conditions for all cannabinoids were determined at a temperature of 60 °C and a pressure of 300 bar to 550 bar. At higher temperatures and reaction times, a significant depletion of neutral cannabinoids was observed. The optimal conditions of the decarboxylation process varied depending on the component. For the CBD component, which could be measured in the highest concentrations (560 mg/g), the optimal conditions were 140 °C and 10 min. The study can be an important model for predicting the behavior of cannabinoids under certain parameters. Ključne besede: supercritical fluids, extraction, cannabinoids, decarboxilation, Cannabis sativa I Objavljeno v DKUM: 08.01.2025; Ogledov: 0; Prenosov: 2
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2. Mango peels as an industrial by-product: a sustainable source of compounds with antioxidant, enzymatic, and antimicrobial activityNika Kučuk, Mateja Primožič, Petra Kotnik, Željko Knez, Maja Leitgeb, 2024, izvirni znanstveni članek Opis: Plant waste materials are important sources of bioactive compounds with remarkable health-promoting benefits. In particular, industrial by-products such as mango peels are sustainable sources of bioactive substances, with antioxidant, enzymatic, and antimicrobial activity. Appropriate processing is essential to obtain highly bioactive compounds for further use in generating value-added products for the food industry. The objective of the study was to investigate and compare the biological activity of compounds from fresh and dried mango peels obtained by different conventional methods and unconventional extraction methods using supercritical fluids (SFE). The highest total phenolic content (25.0 mg GAE/g DW) and the total content of eight phenolic compounds (829.92 µg/g DW) determined by LC-MS/MS were detected in dried mango peel extract obtained by the Soxhlet process (SE). SFE gave the highest content of proanthocyanidins (0.4 mg PAC/g DW). The ethanolic ultrasonic process (UAE) provided the highest antioxidant activity of the product (82.4%) using DPPH radical scavenging activity and total protein content (2.95 mg protein/g DW). Overall, the dried mango peels were richer in bioactive compounds (caffeic acid, chlorogenic acid, gallic acid, catechin, and hesperidin/neohesperidin), indicating successful preservation during air drying. Furthermore, outstanding polyphenol oxidase, superoxide dismutase (SOD), and lipase activities were detected in mango peel extracts. This is the first study in which remarkable antibacterial activities against the growth of Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) were evaluated by determining the microbial growth inhibition rate after 12 and 24 h incubation periods for mango peel extracts obtained by different methods. Ethanolic SE and UAE extracts from dried mango peels resulted in the lowest minimum inhibitory concentrations (MIC90) for all bacterial species tested. Mango peels are remarkable waste products that could contribute to the sustainable development of exceptional products with high-added value for various applications, especially as dietary supplements. Ključne besede: mangifera indica, peels, bioactive substances, LC-MS/MS, proteins, enzymes, antibacterial activity Objavljeno v DKUM: 12.08.2024; Ogledov: 104; Prenosov: 8
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3. Degradation of waste tetra pak packaging with hydrothermal treatment in sub-/supercritical waterMihael Irgolič, Maja Čolnik, Petra Kotnik, Mojca Škerget, 2024, izvirni znanstveni članek Ključne besede: hydrothermal degradation, waste packing, tetra pak, subcritical water, subcritical waste, chemical recycling, one-stage process, two-stage process, product analysis Objavljeno v DKUM: 16.07.2024; Ogledov: 88; Prenosov: 20
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4. Extraction of active compounds from mixtures of hemp (Cannabis sativa) with Pants of the Zingiberaceae familyVesna Postružnik, Taja Žitek Makoter, Darko Goričanec, Petra Kotnik, Željko Knez, Maša Knez Marevci, 2023, izvirni znanstveni članek Ključne besede: supercritical fluid extraction, ultrasound-assisted extraction, hemp, ginger, turmeric, cardamom Objavljeno v DKUM: 08.05.2024; Ogledov: 234; Prenosov: 13
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5. Comparative study of hydrothermal decomposition of virgin and recycled polypropyleneMihael Irgolič, Maja Čolnik, Petra Kotnik, Lidija Čuček, Mojca Škerget, 2023, izvirni znanstveni članek Opis: Plastics are widely used due to their versatile properties and numerous applications. However, the proper management of plastic waste is a major challenge, even though it is recyclable. The process of repeated recycling can cause the quality of the material to decrease as unwanted contaminants and pollutants increase. This can affect the chemical recycling of plastics at the end of their life and the recovery of secondary products that can be used in other applications. In this study, the chemical degradation of virgin polypropylene (vPP) and recycled polypropylene (rPP) was investigated in supercritical water at a temperature of 450 °C and a reaction time of 15 to 240 min. The oil phase was the primary decomposition product and was obtained in high yield, which reached a maximum after 30 min of reaction time and was 96.9 % for vPP and 94.5 % for rPP. The results of our study show that there are some differences in the product composition depending on which material (vPP or rPP) is chemically recycled. Ključne besede: virgin polypropylene, plastics, chemical degradation, chemical recycled Objavljeno v DKUM: 18.04.2024; Ogledov: 235; Prenosov: 5
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6. The extraction process, separation, and identification of curcuminoids from turmeric curcuma longaGal Slaček, Petra Kotnik, Azra Osmić, Vesna Postružnik, Željko Knez, Matjaž Finšgar, Maša Knez Marevci, 2023, izvirni znanstveni članek Opis: Turmeric Curcuma longa is a well-known spice with various health benefits, attributed primarily to curcumin. Soxhlet extraction, cold maceration, ultrasound-assisted extraction (UAE), and supercritical fluid extraction were performed, and the content of total phenols, proanthocyanidins, and antioxidants was analysed by UV/VIS spectrophotometry. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was employed to identify and quantify the curcumin content. Supercritical extracts had the highest total phenolic content (538.95 mg GA/100 g material), while the Soxhlet extracts had the highest content of proanthocyanidins (4.77 mg PAC/100 g of material). Extracts obtained by UAE and supercritical extraction have the highest antioxidant potential. Antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH center dot) was 64.27% and 1750.32 mg Trolox per g dry weight by 2,2-azinobis(3-ethylbenzothiazoline 6 sulphonic acid) (ABTS(+center dot)) for the extract obtained by supercritical extraction. The UAE resulted in the highest amount of curcumin (1.91 mg curcumin/g material). A kinetic study showed that extraction yield in supercritical extracts decreased with increasing temperature and that the content of isolated curcumin was inversely proportional to solvent-to-feed ratio (S/F). The present study has confirmed that turmeric is an excellent source of antioxidants, such as curcumin, that play an important role in reducing cellular stress by neutralising free radicals. Ključne besede: turmeric, curcumin, total phenols, proanthocyanidins, antioxidants Objavljeno v DKUM: 09.02.2024; Ogledov: 361; Prenosov: 44
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7. Degradation of polyvinyl chloride (PVC) waste with supercritical waterMaja Čolnik, Petra Kotnik, Željko Knez, Mojca Škerget, 2022, izvirni znanstveni članek Opis: The chemical degradation of PVC waste in SCW between 400 and 425 °C and reaction times from 30 to 60 min was studied. The PVC waste in SCW decomposed into the gas, oil, water soluble, and solid phases. The highest yield of the gas and oil phases was achieved at the temperature of 425 °C after 60 min. By increasing the reaction time at 400 °C, the yield of chloride ions in the aqueous phase increased and reached the maximum at 60 min. The gas and oil phases contained many valuable compounds similar to crude oil. Alkanes and chloroalkanes; alkenes, alicyclic, and aromatic hydrocarbons; as well as alcohols were the main groups of hydrocarbons in the oil phase, while the gas phase contained only light hydrocarbons (C1–C6), CO2, and small amounts of H2. This confirmed that the largest chlorine content remains in the aqueous phase and does not pass into the gas phase. It can be concluded that SCW presents effective decomposition media for plastic waste. Ključne besede: polyvinyl chloride, supercritical water, chemical recycling, plastic waste Objavljeno v DKUM: 18.09.2023; Ogledov: 513; Prenosov: 42
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8. Chemical recycling of polyolefins waste materials using supercritical waterMaja Čolnik, Petra Kotnik, Željko Knez, Mojca Škerget, 2022, izvirni znanstveni članek Opis: In the following work, the hydrothermal degradation of polypropylene waste (PP) using supercritical water (SCW) has been studied. The procedure was carried out in a high-pressure, high-temperature batch reactor at 425 °C and 450 °C from 15 to 240 min. The results show a high yield of the oil (up to 95%) and gas (up to 20%) phases. The gained oil phase was composed of alkanes, alkenes, cycloalkanes, aromatic hydrocarbons, and alcohols. Alkanes and alcohols predominated at 425 °C and shorter reaction times, while the content of aromatic hydrocarbons sharply increased at higher temperatures and times. The higher heating values (HHVs) of oil phases were in the range of liquid fuel (diesel, gasoline, crude and fuel oil), and they were between 48 and 42 MJ/kg. The gas phase contained light hydrocarbons (C1–C6), where propane was the most represented component. The results for PP degradation obtained in the present work were compared to the results of SCW degradation of colored PE waste, and the potential degradation mechanism of polyolefins waste in SCW is proposed. The results allowed to conclude that SCW processing technology represents a promising and eco-friendly tool for the liquefaction of polyolefin (PE and PP) waste into oil with a high conversion rate. Ključne besede: polypropylene, polyolefins, supercritical water, plastics waste, chemical recycling Objavljeno v DKUM: 18.09.2023; Ogledov: 555; Prenosov: 32
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9. Primerjava nekaterih kemijskih lastnosti različnih vrst medu : diplomsko delo univerzitetnega študijskega programa I. stopnjeJure Martinuzzi, 2023, diplomsko delo Opis: Med se že stoletja uporablja kot naravno sladilo, v zadnjih letih tudi zaradi zdravilnih učinkov. V diplomski nalogi smo s pomočjo spektrofotometrične metode določevali celokupne ogljikove hidrate, vsebnost celokupnih fenolnih spojin ter antioksidativnost (DPPH). S pomočjo visoko zmogljive tankoplastne kromatografije (HPTLC) smo določevali vsebnosti posameznih ogljikovih hidratov (glukoza, fruktoza, saharoza in maltoza). Za določevanje smo pripravili raztopine vzorcev domačega akacijevega, cvetličnega, kostanjevega in ajdovega medu.
V posamezni vrsti medu smo uspešno določili posamezne ogljikove hidrate ter njihovo vrednost. Najvišjo vsebnost glukoze smo izmerili v akacijevem medu, nekoliko manj v cvetličnem, kostanjevem in ajdovem. Delež glukoze je bil najvišji v cvetličnem medu, najnižji v akacijevem medu. V vzorcu akacijevega in cvetličnega medu smo zaznali nizko vrednost saharoze, medtem ko v kostanjevem in ajdovem medu saharoze nismo zaznali. Fruktoza in glukoza imata pomembno vlogo pri kristalizaciji. Akacijev med, ki je bil analiziran, ima visoko vrednost razmerja fruktoza/glukoza (F/G), zato ne kristalizira, medtem ko ima cvetlični med nizko razmerje F/G in kristalizira precej hitro. Dokazali smo, da se vsebnost antioksidantov ter vsebnost celokupnih fenolnih spojin v medu spreminja na podlagi barve medu. Akacijev in cvetlični med sta svetlejša, imata nižje zaznane vsebnosti antioksidantov ter celokupnih fenolnih spojin kot kostanjev med in ajdov med, ki sta temnejša meda. Ključne besede: med, sladkorji, antioksidativnost, HPTLC, celokupne fenolne spojine Objavljeno v DKUM: 11.09.2023; Ogledov: 567; Prenosov: 0
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10. Izolacija eteričnih olj iz poprove mete ( mentha piperita) : diplomsko delo univerzitetnega študijskega programa I. stopnjeLiza Curk, 2023, diplomsko delo Opis: Pri diplomski nalogi smo iz poprove mete, lat. Mentha piperita, izolirali eterična olja z različnimi kovnencionalnimi in nekonvencionalnimi metodami. Pri vseh ekstrakcijskih metodah smo uporabili tri topila, metanol, etanol in petroleter, z izjemo Clevengerjeve destilacije, kjer je topilo voda. Nato smo ekstrakte analizirali na vsebnost lahkohlapnih komponent in kvalitativno in kvantitativno določili sestavo olj s pomočjo plinske kromatografije z masno spektrometrijo. Identificiranih je bilo 71 komponent, v najvišjih deležih pa se v eteričnem olju pojavljajo mentol (37,7 %), menton (31,2 %), neomentol (3,3 %), piperiton (2,6 %) in mentil acetat (2,6 %). Ugotovljeno je bilo, da so bili najvišji izkoristki ektrakcij doseženi z ekstrakcijo po Soxhletu, čeprav so bili v splošnem izkoriski zelo nizki. Preučevali smo tudi vpliv topila na izkoristek ekstrakcije in ugotovili, da je najprimernejše topilo metanol, pri analizi vsebnosti pa lahko vidimo, da so se pri vseh treh topilih izločale enake glavne komponente. Poleg tega so rezultati pokazali, da so bile kemične sestavine eteričnih olj pri vseh metodah podobne z manjšimi količinskimi razlikami. Ključne besede: izolacija, separacija, GC-MS, eterična olja, destilacija Objavljeno v DKUM: 06.09.2023; Ogledov: 922; Prenosov: 0
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