385 results on '"Strelec, Ivica"'
Search Results
2. Transformation of eggshell waste to egg white protein solution, calcium chloride dihydrate, and eggshell membrane powder
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Strelec Ivica, Ostojčić Marta, Brekalo Mirna, Hajra Sugato, Kim Hoe-Joon, Stanojev Jovana, Maravić Nikola, and Budžaki Sandra
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eggshell waste utilization ,adherent egg white proteins ,eggshell membranes ,calcium chloride ,lysozyme ,Chemistry ,QD1-999 - Abstract
The present study investigated the possibility of complete utilization of eggshell waste (ESW) transforming it to adherent egg white protein solution, calcium chloride dihydrate, and eggshell membranes (ESM). Adherent egg white protein solution was obtained by washing ESW three times with distilled water at 25°C, followed by filtration, and analyzed for the protein content and lysozyme activity. ESM and calcium chloride were obtained simultaneously by the exposure of washed eggshells to 5% hydrochloric acid treatment at 25°C for 3 h, followed by separation by filtration. The separated ESM were washed, dried, and milled to powder and analyzed for protein and lipid content. The calcium chloride solution was exposed to the neutralization of excess hydrochloric acid by calcium hydroxide, followed by evaporation to one-tenth of volume. Calcium chloride crystals were precipitated from the concentrated solution with acetone, separated by filtration, dried at 110°C, and analyzed for chemical composition and purity. The obtained results revealed that 100 g of ESW can be transformed to 1.61 ± 0.34 g of adherent white proteins containing 485,821 U of lysozyme activity, 2.84 ± 0.16 g of ESM powder, and 108.74 ± 3.62 g of calcium chloride dihydrate of high purity. more...
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- 2023
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3. Biochemical and Quality Parameter Changes of Wheat Grains during One-Year Storage under Different Storage Conditions
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Strelec, Ivica, primary, Mrša, Vladimir, additional, Simović, Dragana Šoronja, additional, Petrović, Jovana, additional, Zahorec, Jana, additional, and Budžaki, Sandra, additional
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- 2024
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4. Multistep Extraction Transformation of Spent Coffee Grounds to the Cellulose-Based Enzyme Immobilization Carrier
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Brekalo, Mirna, primary, Rajs, Blanka Bilić, additional, Aladić, Krunoslav, additional, Jakobek, Lidija, additional, Šereš, Zita, additional, Krstović, Saša, additional, Jokić, Stela, additional, Budžaki, Sandra, additional, and Strelec, Ivica, additional more...
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- 2023
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5. Impact of fullerol C60(OH)24 nanoparticles on the production of emerging toxins by Aspergillus flavus
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Kovač, Tihomir, Borišev, Ivana, Kovač, Marija, Lončarić, Ante, Čačić Kenjerić, Frane, Djordjevic, Aleksandar, Strelec, Ivica, Ezekiel, Chibundu N., Sulyok, Michael, Krska, Rudolf, and Šarkanj, Bojan
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- 2020
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6. Croatian produced unifloral honey characterized according to the protein and proline content and enzyme activities
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Flanjak Ivana, Strelec Ivica, Kenjerić Daniela, and Primorac Ljiljana
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croatia ,enzyme activity ,honey ,proline content ,protein content ,Zoology ,QL1-991 - Abstract
In honey, the content of proteins, including the enzymes, is relatively low and has a minor nutritive significance. On the other hand, the proteins, including the enzymes, are usually used as honey quality evaluation parameters. This is because protein content and enzyme activities vary regarding the botanical origin of the honey. Since the results of protein content, glucose-oxidase, and acid phosphatase, for honeys produced in Croatia, are not available, four of the most abundant honey types produced in Croatia (black locust, sage, chestnut, and honeydew honey) are characterised according to the protein and proline content and enzyme activities. The characterisation was done to determine specificities and contribute to the characterisation of unifloral honeys. Dark honey types (honeydew and chestnut honey) had a higher proline content, and diastase, invertase, and glucose-oxidase activity than lighter sage and black locust honey. Black locust honey has a naturally low enzyme activity and showed the highest acid phosphatase activity among the analysed honey types, while honeydew honey, otherwise known to possess high proline content and enzyme activity, had a low protein content comparable to black locust honey. Statistically significant correlations were obtained between all analysed parameters, with the exception of acid phosphatase activity. more...
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- 2016
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7. Characterization of Croatian Honeys by Right-Angle Fluorescence Spectroscopy and Chemometrics
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Strelec, Ivica, Brodar, Lidija, Flanjak, Ivana, Čačić Kenjerić, Frane, Kovač, Tihomir, Čačić Kenjerić, Daniela, and Primorac, Ljiljana
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- 2017
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8. Effect of process parameters on biodiesel production from edible and waste oils by Burkholderia cepacia lipase
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Ostojčić, Marta, Bilić Rajs, Blanka, Tišma, Marina, Budžaki, Sandra, and Strelec, Ivica
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biodiesel ,Burkolderia cepacia lipase ,waste oils ,iodine value - Abstract
Although biodiesel has been on the market for many years as an alternative to fossil fuels and its production is carried out through the already known routes of chemical transesterification, the need for development of more environmentally friendly production using lipase is still in the focus. To gain insight into the effects of several process parameters on the biocatalytic biodiesel production, we have characterised Burkolderia cepacia lipase and used it in the production of biodiesel from edible and waste cooking oils and fats at previously optimised pH and T. In addition, characterization of the feedstock including fatty acid profile, percentage of free fatty acids, peroxide and iodine value was performed. The results showed that at optimized process conditions after one hour of reaction time, 250 U of the lipase per 1 g of reaction mixture was sufficient to achieve fatty acid methyl ester content of 99% when fresh edible oil was used as feedstock, while 97% of FAME was reached when waste cooking oil/fat was used as feedstock. Iodine value, as one of the indicators of oil/fat quality, showed statistically significant correlation with fatty acid methyl esters content, what indicates that it can be used as one of the indicators for selecting feedstock for enzymatic production of biodiesel. more...
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- 2023
9. Fullerol C60(OH)24 nanoparticles modulate aflatoxin B1 biosynthesis in Aspergillus flavus
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Kovač, Tihomir, Borišev, Ivana, Crevar, Biljana, Čačić Kenjerić, Frane, Kovač, Marija, Strelec, Ivica, Ezekiel, Chibundu N., Sulyok, Michael, Krska, Rudolf, and Šarkanj, Bojan
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- 2018
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10. Simulated Gastric and Intestinal Fluid Electrolyte Solutions as an Environment for the Adsorption of Apple Polyphenols onto β-Glucan
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Jakobek, Lidija, primary, Strelec, Ivica, additional, Kenjerić, Daniela, additional, Šoher, Lidija, additional, Tomac, Ivana, additional, and Matić, Petra, additional
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- 2022
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11. Eggshell-Waste-Derived Calcium Acetate, Calcium Hydrogen Phosphate and Corresponding Eggshell Membranes.
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Strelec, Ivica, Tomičić, Klara, Zajec, Marko, Ostojčić, Marta, and Budžaki, Sandra
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CALCIUM phosphate ,EGGSHELLS ,ACETATES ,CALCIUM ,CHEMICAL yield ,FORMIC acid - Abstract
Featured Application: Calcium acetate monohydrate and calcium hydrogen phosphate anhydrous of food-grade additive purity, as well as corresponding eggshell membranes as a valuable by-product, has been produced from eggshell waste by commonly used industrial processes which might be easily transferable on the industrial scale level. The development of innovative transformation techniques for various wastes generated by the agri-food industry is one of the goals of sustainable waste management oriented toward "zero-waste" approach. This includes the production of bulk and fine chemicals, bioactive compounds, enzymes and functional materials from various waste. The present research shows the possibility of the production of value-added products from eggshell waste using chemical transformation by acetic and o-phosphoric acid at a laboratory scale level. Eggshell-derived calcium acetate monohydrate and calcium hydrogen phosphate, both of high purity, as well as corresponding eggshell membranes as valuable by-products, were produced. Chemical transformation of 100 g of eggshell waste with 10% (w/v) acetic acid resulted in 111.41 ± 2.13 g of calcium acetate monohydrate and 2.90 ± 0.14 g of eggshell membranes, with a chemical yield in calcium acetate monohydrate of 79.16 ± 1.98%. On the other hand, the transformation of 100 g of eggshell waste in 15% (w/v) o-phosphoric acid yielded 77.06 ± 6.21 g of calcium hydrogen phosphate and 2.94 ± 0.08 g of eggshell membranes, with a chemical yield in calcium hydrogen phosphate of 71.36 ± 5.58%. Eggshell-derived calcium hydrogen phosphate met all prescribed criteria for food-grade additive, as determined by physicochemical analysis. On the other hand, calcium acetate monohydrate met the majority, except water insoluble and formic acid and oxidizable impurities content. Based on the obtained results, it can be concluded that the proposed eggshell waste transformation process by two different acids might be useful for the production of calcium acetate and calcium hydrogen phosphate as food-grade additives, as well as eggshell membranes as valuable by-products. [ABSTRACT FROM AUTHOR] more...
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- 2023
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12. Spectrofluorimetric, spectrophotometric and chemometric analysis of wheat grains infested by Sitophilus granarius
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Strelec, Ivica, Kučko, Lucija, Roknić, Dragica, Mrša, Vladimir, and Ugarčić-Hardi, Žaneta
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- 2012
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13. Green Synthesis of Thiazolidine-2,4-dione Derivatives and Their Lipoxygenase Inhibition Activity With QSAR and Molecular Docking Studies
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Lončarić, Melita, primary, Strelec, Ivica, additional, Pavić, Valentina, additional, Rastija, Vesna, additional, Karnaš, Maja, additional, and Molnar, Maja, additional
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- 2022
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14. Immobilization of lipases on functionalised carriers produced from selected agro-food industrial waste
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Budžaki, Sandra, Šereš, Zita, Strelec, Ivica, and Pajin, Biljana
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agro-food industry waste ,lipase immobilization ,eggshells ,spent coffee grounds ,brown onion skin - Abstract
One of the main challenges of the agro-food industry sustainable waste management by “zero- waste” model is the application of the circular management strategy, including development of innovative waste transformation techniques. Agro- food waste transformation into carriers for enzyme immobilization clearly represent one of such techniques, while replacement of chemical catalysts with immobilized enzymes might solve the issues of energy efficiency and environmental acceptability. On the other hand, process economic cost-effectiveness is highly dependent on the immobilized enzyme price. Whether the agro-food waste transformation could result with cost effective enzyme carriers for lipase immobilization, and subsequent development of immobilized lipases of desirable operational properties for use in the biocatalytic production, is the question this project aiming to answer. In this respect, carriers of desirable operational properties and high immobilization capacity will be prepared from selected waste: eggshells, spent coffee grounds and brown onion skin followed by subsequent immobilization of Pseudomonas fluorescens and Burkholderia cepacia lipases using various immobilization techniques. Biochemical and operational properties of free and immobilized lipases will be used for the selection of developed immobilized lipases of the greatest efficiency, which will be tested for operational functionality in the selected reactions of acidolysis, hydrolysis and transesterification. The final proof will be confirmed by industrial scale techno-economic analysis simulation, as well as life cycle analysis. more...
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- 2022
15. Rhodanine derivatives as potent mushroom tyrosinase inhibitors
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Lončarić, Melita, Strelec, Ivica, Molnar, Maja, Dulić, M., Sinčić, N., and Madunić, I.V.
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mushroom tyrosinase ,inhibition ,rhodanine derivatives - Abstract
Tyrosinases are enzymes belonging to the type-3 copper protein family which contains two copper ions in the active site. These oxidoreductases perform two sequential enzymatic reactions: hydroxylation of monophenols followed by oxidation of diphenols forming quinones which polymerize spontaneously to melanin. Tyrosinases are found in different prokaryotes as well as in plants, fungi, arthropods, and mammals. Besides its positive role in various organisms, like wound healing, sclerotization and pigmentation of insect cuticles, defence against herbivores and pathogens in plants, tyrosinases also can have negative impacts on humans (senile lentigo, melisma, freckles and pigmented ace scars) and plants (browning in fruit and vegetables following cell damage). Therefore, development of new potent tyrosinase inhibitors in medicine and cosmetic industry, as well in the food industry, is of interest. In this research 30 differently substituted rhodanine derivatives as possible mushroom tyrosinase inhibitors were tested with both, L-tyrosine and L-DOPA as substrates. Rhodanine derivatives were synthesized with green method in deep eutectic solvents without usage of organic solvents or harmful catalysts. Synthesised rhodanines inhibited tyrosinase in the range 4.2 - 100.0 % and 1.1 - 100.0 % with L-DOPA and L- tyrosine as substrates, respectively. Compound 3- allyl-5-(3-hydroxy-4-methoxybenzylidene)-2- thioxothiazolidin-4-one showed 100.0 % of tyrosinase inhibition when using both substrates. Tyrosinase inhibition of 100.0 % was also achieved with compounds 3-allyl-5-(4-(benzyloxy)-2- hydroxybenzylidene)-2-thioxothiazolidin-4-one and 3-amino-5-(3-hydroxy-4-methoxybenzylidene)-2- thioxothiazolidin-4-one but with L-tyrosine as substrate. The lowest IC50 values of 0.30 µM in case of L-DOPA and 0.23 µM in case of L-tyrosine were determined for compounds 3-allyl-5-((E)-3- phenylallylidene)-2-thioxothiazolidin-4-one and 3- amino-5-(3-hydroxy-4-methoxybenzylidene)-2- thioxothiazolidin-4-one, respectively. more...
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- 2022
16. Transformation of spent coffee grounds to high-value added products
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Brekalo, Mirna, Aladić, Krunoslav, Jakobek Barron, Lidija, Bilić-Rajs, Blanka, Stanojev, Jovana, Maravić, Nikola, Budžaki, Sandra, Strelec, Ivica, and Babić, Jurislav
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spent coffee grounds ,transformation ,coffee oil ,caffeine ,enzyme immobilization carriers - Abstract
Development of innovative transformation techniques of waste generated by agri-food industry into high-value added products, is one of pillars of circular economy oriented toward “zero- waste” approach. In this respect, we have examined the possibility of complete utilization of spent coffee grounds using sequential extraction by several solvents, followed by alkaline liquefaction of solid residue. Soxhlet extraction of spent coffee grounds with n-hexane has been used for the production of coffee oil, while continuous sequential subcritical extraction of defatted residue by 96% and 50% ethanol, and water for the production of targeted bioactive compounds. The solid residue remained after sequential subcritical extraction was subjected to alkaline liquefaction in order to produce possible carrier for enzyme immobilization. The complete utilization of 100 g of spent coffee ground containing 95 % of dry matter resulted with the production of 10.5 g of coffee oil rich in linoleic and palmitic acid, 330 mg of caffeine and 120 mg of chlorogenic acid, and with 20 g of chemically inert cellulose carrier for the enzyme immobilization. Based on the current evidence, it can be safely concluded that spent coffee grounds represent the valuable raw-material for the production of high value-added products, instead being discarded on landfills. more...
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- 2022
17. Transformacijski potencijal otpadne biomase luka
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Brekalo, Mirna, Stjepanović, Marija, Strelec, Ivica, Budžaki, Sandra, Šubarić, Drago, Jokić, Stela, and Lončarić, Ante
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otpadna biomasa luka ,kvercetin ,prehrambena vlaka ,oporaba - Abstract
Luk je jedna od često korištenih namirnica, čija otpadna biomasa nakon proizvodnje i industrijske prerade završava na otpadu, što predstavlja značajno ekološko i ekonomsko opterećenje kako za industriju tako i po okoliš. Sukladno tome, inovativne tehnike obrade i iscrpljivanja otpadne biomase luka dobivaju sve više na važnosti. Otpadna biomasa luka se ističe kao visokovrijedna sirovina za daljnje iskorištenje zbog osebujnog kemijskog sastava koji uključuje visok udio prehrambenih vlakana, minerala, antioksidanasa, organo-sumpornih spojeva i dominantnog flavonola kvercetina. Sukladno tome, posjeduje veliki potencijal za proizvodnju i uporabu funkcionalnih sastojaka u poboljšanju postojećih i/ili razvoju novih prozvoda prehrambene industrije. Uz navedeno, biomasa luka je potencijalna sirovina za proizvodnju biomaterijala, biogoriva i bioenergije. more...
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- 2022
18. How biotechnology met circular economy at the Faculty of Food Technology Osijek
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Velić, Natalija, Tišma, Marina, Krstanović, Vinko, Strelec, Ivica, Marček, Tihana, Kovač, Tihomir, and Komes, Draženka
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biotechnology ,circular economy ,Faculty of Food Technology Osijek - Abstract
Since food is inseparable from biotechnology, it is not surprising that food biotechnology has been included in the curriculum of the Faculty of Food Technology Osijek, University of Osijek (PTFOS) since its foundation some 50 years ago. The choice of research topics of a small core of researchers in the field of biotechnology at PTFOS, which has grown over the years, was also mainly related to food biotechnology and included the study of abiotic and biotic stress factors of crops, enzyme activities related to grain storage, the study of mycotoxigenic fungi related to food and feed safety, enzyme (bio)catalysis and the general improvement of biotechnological methods for the production of fermented foods (especially beverages, beer and fruit wine). However, the emerging need for the food industry to move to more sustainable primary production and processing systems has led to a rethinking of how resources are used within traditional food processing systems, e.g. the production residues from the agri-food industry have been recognised as a valuable resource for the production of high-value products and biofuels. This is where biotechnology and the circular economy met at PTFOS. The European Commission defines the circular economy as a model in which the generation of waste is minimised and the value of products, materials and resources is retained for as long as possible, so that what was once considered waste becomes a resource. Production residues, i.e., by-products and waste materials, from the food industry, including the same fermentation technologies that were the subject of research at PTFOS, are now being reused for the isolation of biologically active compounds, the production of enzymes, biofuels, and other valuable products, or as enzyme carriers and biosorbents. An overview will be given of the previous research topics and projects in the field of biotechnology, as well as the topics and projects related to biotechnology and the circular economy that are currently being carried out at PTFOS. more...
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- 2022
19. Preparation of Amino Acid-Functionalized Carbon Quantum Dots Using Clementine Peel – Potential Application in Biomedical Analysis and as Fluorescent Probe for Fe3+ Detection
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Šafranko, Silvija, Strelec, Ivica, Dutour- Sikirić, Maja, Weber, Igor, Herak Bosnar, Maja, Grbčić, Petra, Kraljević Pavelić, Sandra, Széchenyi, Aleksandar, Janđel, Kristina, Kovačević, Monika, Jokić, Stela, Dulić, Morana, Sinčić, Nino, and Vrhovac Madunić, Ivana more...
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carbon quantum dots ,sensing ,pharmaceutical analysis - Abstract
Luminiscent carbon quantum dots (CQDs) are widely known as zero-dimensional nanomaterials which have attracted extensive attention, especially in green chemistry and biomedicine. Due to their excellent biocompatibility and low toxicity, water solubility, stability in high ionic media and great optical properties, CQDs have been widely used as functional optical materials in fluorescence sensing. In this study, preparation and modification of CQDs using clementine peel as carbon precursor and amino acids with different chemical complexity (glycine and arginine - nitrogen dopants) has been presented. It has been demonstrated that increasing nitrogen content in CQDs samples has increased the quantum yield percentage of prepared CQDs. Some differences in sample properties were observed regarding structural and chemical diversity, biological and antioxidant activity. The antiproliferative effect of CQD@Gly against pancreatic cancer cell lines (CFPAC-1) was demonstrated. Based on the DPPH assay results, the CQD@Arg demonstrated the highest antiradical activity 81.39 ± 0.39%, and EC50 was determined to be EC50 = 53.78 ± 0.97 µg/mL (R2 = 0.9357). Furthermore, due to the highest determined quantum yield, CQD@Arg sample was further used for the ion sensing and cellular imaging of cancer cells. The CQD@Arg was applied as a fluorescent nanoprobe for Fe3+ detection, with a good linear correlation in the concentration range from 7.0 µmol dm−3 to 50.0 µmol dm−3 with R2 = 0.9931 and limit of detection (LOD) of 4.57 ± 0.27 µmol dm−3. In order to investigate the applicability of prepared CQDs in cell imaging, MCF-7 cells were incubated with CQD@Arg and imaged by confocal microscopy. This study implies the potential application of the prepared CQDs in bioimaging and ion sensing, and also as a fluorescent probe with diverse biological and pharmacological activities in general. more...
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- 2022
20. A step toward complete utilization of eggshell waste
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Strelec, Ivica, Aladić, Krunoslav, Ostojčić, Marta, Harja, Sugato, Kim, Hoe-Joon, Maravić, Nikola, Stanojev, Jovana, Budžaki, Sandra, and Šereš, Zita
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eggshell waste utilization ,adherent egg white protein ,eggshell membranes ,calcium salts - Abstract
One of the five major challenges of sustainable waste management in the agri-food industry by using the "zero-waste" model of the circular economy is the development of innovative waste transformation techniques for the production of chemicals, fine chemicals, bioactive compounds, enzymes and functional materials. These products have at least twice added value of products obtained from currently dominant outdated waste management strategies which are not in accordance with sustainable development. Eggshell waste is one on the wastes produced by agri-food industry whose majority instead being re-used, ends in landfill sites, additionally burdening the environment. Situation is quite concerning if one considers that at least 7, 894, 962 t of eggshell waste was generated annually worldwide of which 777, 000 t in the European Union in 2018. Keeping in mind current state of eggshell waste utilization/landfilling and the need for the development of innovative waste transformation techniques, we have designed “3 from 1” process of complete utilization of eggshell waste oriented toward “zero-waste” model. The process included eggshell waste washing, acid solvation and few additional steps for preparation of powdered calcium salts and eggshell membranes. After complete utilization of eggshell waste: clarified adherent egg white protein solution, three different types of eggshell membranes and three different calcium salts: calcium chloride, calcium acetate and calcium hydrogen phosphate of high purity was produced. In addition, spry-drying for the production of anhydrous calcium chloride was implemented. Based on results obtained, it can be concluded that designed “3 from 1” process has great potential to be used not only for the complete utilization of eggshell waste, but also for the production of high-value added products from it. more...
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- 2022
21. Preparation and Characterization of N-Doped/Hybrid Carbon Quantum Dots and Their Application in Metal Ion Detection
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Šafranko, Silvija, Strelec, Ivica, Jokić, Stela, Antunović, Zvonko, and Mihajlović, Anea
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carbon quantum dots ,nanoparticle functionalization ,metal ion detection ,bioactivity - Abstract
Carbon quantum dots (CQDs) represent a new class of efficient carbon photoluminescent nanomaterials that have attracted the attention of many scientists over the past decade, especially due to their excellent chemical and optical properties. In general, carbon dots are defined as zero- dimensional carbon-based nanoparticles with a diameter less than 20 nm, while the specific applicability mostly depend on the nanoparticle size, shape, composition, and surface features. Their high chemical and photo-stability, biocompatibility/low toxicity, tunable emission, water solubility and optical efficiency represent a huge potential for a wide range of applications in biomedical research and nanotechnology. This work presents a comparative study of the CQDs preparation from Citrus clementina peel and citric acid. In order to obtain best performing hybrid nanoparticles (CQD@hybrid), pre-optimization regarding synthetic conditions, type and quantity of added amino acids has been performed. The main aim of this study was to enhance quantum yield (QY) of prepared samples, also to improve their bioactivity, and to achieve selective response toward Fe3+ ions. The highest quantum yield was determined with CQD@hybrid obtained with the addition of amino acid leucine (Leu), treated at temperature of 200°C for 12 hours, and this sample was further investigated for the Fe3+ ion sensing. The developed model was described by an exponential function with a suitable coefficient of determination of R2 = 0.9851, while the linear range was determined in the concentration range from 0.5 μmol dm-3 to 15 μmol dm-3 with a determined limit of detection of LOD = 2.72 ± 0.39 μmol dm-3 and limit of quantification of LOQ = 9.06 ± 1.29 μmol dm-3. The developed model has been tested for the Fe3+ ions detection in real sample systems of well water samples. These presented results are indicative of a good preparative approach toward obtaining highly fluorescent CQDs, showing also good stability in aqueous media with significant differences in optical properties, while showing great potential for the studies in biological systems and water monitoring. more...
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- 2022
22. Transformation of Eggshells, Spent Coffee Grounds, and Brown Onion Skins into Value-Added Products
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Budžaki, Sandra, Strelec, Ivica, and Velić, Natalija
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eggshells ,spent coffee grounds ,brown onion skins ,value-added products ,“zero-waste” model ,eggshells, spent coffee grounds, brown onion skins, value-added products, “zero-waste” model - Abstract
Unlike other wastes from the agri-food industry (straw, corn, cob, stalks, seeds, husks) widely used in biorefineries as feedstock for the production of high-value products (chemicals, biofuels and bioenergy), eggshells, spent coffee grounds, and brown onion skins have not yet found a suitable place in sustainable production, but are mainly landfilled burdening the environment. This paper aims to point out the great potential of eggshells, spent coffee grounds, and brown onion skins as secondary raw materials in sustainable development, with minimal production of waste streams. more...
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- 2022
23. Preparation of Amino Acid Functionalized Carbon Quantum Dots from Citric Acid Efficient Fluorescent Nanoprobe for Selective Detection of Fe3+ Ions in Model Systems and in Well Water Samples
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Šafranko, Silvija, Janđel, Kristina, Kovačević, Monika, Dutour Sikirić, Maja, Mandić, Šimun, Széchenyi, Aleksandar, Strelec, Ivica, and Jokić, Stela
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carbon quantum dots ,sensing ,water analysis - Abstract
Carbon quantum dots (CQDs) represent a new and efficient form of carbon photoluminescent nanomaterials that have attracted enormous attention among the scientific community in the last few decades due to their excellent chemical and optical properties. Their chemical stability, biocompatibility/low toxicity, water solubility and optical efficiency represent a huge potential for a wide range of applications, especially in biomedical research and nanotechnology. CQDs are defined as zero-dimensional carbon nanomaterials, with typical sizes less than 10 nm, however, some literature report the preparation of spherical CQDs particles with a size diameter of approximately 50 nm. It is known that CQDs consist of a carbon core with a high content of sp3- hybridized carbon atoms, and a slightly lower content of sp2-hybridized carbon atoms. One of the many advantages of CQDs is the ability to tune the photoluminescent characteristics by variations in the size of the synthesized particles, the incorporation of different heteroatoms into the structure, or by the addition of functional groups to the particle surface, all to facilitate interactions with biological materials and to increase quantum yield (QY). Due to these characteristics, CQDs find various applications in theranostics, but also in sensing of different chemical species, including metal ions and biomolecules. CQDs can be synthesized by two different synthetic methods ; top-down and bottom- up approaches. The main advantage of the “bottom– up” approach, regarding the selection of chemical precursors and applying optimal operating conditions, makes “bottom–up” method more favorable technique for obtaining different CQDs. The most commonly reported synthetic routes for CQDs preparation are thermal/combustion techniques due to their simplicity, better variability of using different carbon sources, surface functionalization, environmental friendliness, and lower costs of synthesis. Therefore, this study is an example of amino acid-functionalized CQDs preparation from citric acid by facile hydrothermal synthesis. The prepared N-doped CQDs exhibited excellent optical, physical and chemical properties, and the differences were observed among the five different amino acids used as nitrogen dopants (Leu, Trp, Arg, Ala, His). Compared to the blank sample (without the addition of amino acids), N-doped CQDs have shown significantly higher quantum yield, demonstrating also the potential in cellular imaging. The highest quantum yield of 35.75% with a peak excitation/emission of 340/401 nm was achieved using citric acid and amino acid Leu (CQD@Leu), treated at temperature of 180°C during 9 hours. The prepared samples were investigated toward metal ion selectivity (Ca2+, Cu2+, Fe3+, K+, Hg2+, Mg2+, Al3+, Mn2+, and Na+), and the CQD@Leu showed selective and sensitive response (decrease in the fluorescence intensity) upon the addition of Fe3+ ions. Therefore, CQD@Leu was selected for further investigation in Fe3+ detection in model system and in real well water samples. The developed model was described by an exponential function with a suitable coefficient of determination of R2 = 0.9982, while the linear range was determined in the concentration range from 0.3 mol dm-3 to 30 mol dm-3 with a determined limit of detection of LOD = 1.77±0.01 mol dm-3 and limit of quantification of LOQ = 5.89±0.04 mol dm- 3. These findings could demonstrate the potential application of the prepared N-doped CQDs as a fluorescent nanoprobe in ion sensing, elucidating also the influence of the different amino acids on fluorescence efficiency. The presented study may represent a novel and useful approach for developing low-cost and sensitive nanoprobe for practical applications, including those in analytical chemistry, biomedicine and environmental monitoring. more...
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- 2022
24. A Facile Synthetic Approach toward Obtaining N-Doped Carbon Quantum Dots from Citric Acid and Amino Acids, and Their Application in Selective Detection of Fe(III) Ions.
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Šafranko, Silvija, Janđel, Kristina, Kovačević, Monika, Stanković, Anamarija, Dutour Sikirić, Maja, Mandić, Šimun, Széchenyi, Aleksandar, Glavaš Obrovac, Ljubica, Leventić, Marijana, Strelec, Ivica, Aladić, Krunoslav, and Jokić, Stela more...
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CITRIC acid ,AMINO acids ,QUANTUM dots ,DOPING agents (Chemistry) ,CALCIUM ions ,CHEMICAL properties ,IONS - Abstract
This work reports the preparation of amino acid-functionalized CQDs from citric acid by facile hydrothermal synthesis. The prepared N-doped CQDs exhibited excellent optical, physical, and chemical properties, and the differences were observed among the six different amino acids used as nitrogen dopants (Leu, Trp, Lys, Arg, Ala, His). Compared to the blank sample (without the addition of amino acids), N-doped CQDs have shown significantly higher quantum yield, also demonstrating the potential in metal ion sensing. The highest quantum yield of 36.45%, with a peak excitation/emission of 340/406 nm, was achieved using citric acid and amino acid Leu (CQD@Leu), treated at temperature of 180 °C during 9 h. The prepared samples were investigated toward metal ion selectivity (Ca
2+ , Cu2+ , Fe3+ , K+ , Hg2+ , Mg2+ , Al3+ , Mn2+ , and Na+ ), and the CQD@Leu showed a selective and sensitive response upon the addition of Fe3+ ions. Therefore, CQD@Leu was selected for further investigation in Fe3+ detection in the model system and real well water samples. A developed model was described by a logistic function with a good coefficient of determination of R2 = 0.9982, while the linear range was determined in the concentration range from 0.3 mol dm−3 to 30 mol dm−3 , with a determined limit of detection of LOD = 1.77 ± 0.01 mol dm−3 and limit of quantification of LOQ = 5.89 ± 0.04 mol dm−3 . Furthermore, the results of the in vitro cytotoxicity test (MTT) with normal and tumor cell lines (MRC-5, HeLa, NCI-H358, and CaCo-2) clearly demonstrate the excellent biocompatibility of CQD@Leu. [ABSTRACT FROM AUTHOR] more...- Published
- 2023
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25. Waste Management in the Agri-Food Industry: The Conversion of Eggshells, Spent Coffee Grounds, and Brown Onion Skins into Carriers for Lipase Immobilization
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Budžaki, Sandra, primary, Velić, Natalija, additional, Ostojčić, Marta, additional, Stjepanović, Marija, additional, Rajs, Blanka Bilić, additional, Šereš, Zita, additional, Maravić, Nikola, additional, Stanojev, Jovana, additional, Hessel, Volker, additional, and Strelec, Ivica, additional more...
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- 2022
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26. EFFECT OF PROCESSING AND STORAGE ON SAGE (SALVIA OFFICINALIS L.) HONEY QUALITY
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Flanjak, Ivana, primary, Kenjerić, Daniela, additional, Strelec, Ivica, additional, Bilić Rajs, Blanka, additional, and Primorac, Ljiljana, additional
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- 2022
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27. Synthesis of thiazolidinedione derivatives and their lipoxygenase inhibition
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Lončarić, Melita, Strelec, Ivica, Pavić, Valentina, and Molnar, Maja
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thiazolidinedione ,synthesis ,deep eutectic solvents ,lipoxygenase - Abstract
Thiazolidinediones are heterocyclic compounds, also known as glitazones, which possess thiazolidine core. This class of compounds is used in the production of drugs for the treatment of diabetes mellitus type 2. Depending on the substituents, the thiazolidinedione derivatives may possess different biological activities such as anti-diabetic, anti-cancer, anti-arthritic, anti-inflammatory, anti-microbial and anti- melanoma. Various studies have been performed showing different biological activities of thiazolidinediones associated with enzymes like aldose reductase (ALR2), histone deacetylase (HDAC), phosphoinositide 3-kinases (PI3Ks), pim kinase, mitogen activated protein kinase (MEK), protein tyrosine phosphatase 1B (PTP1B), tyrosinases, cyclooxygenase-2 (COX-2), UDP-N- acetylmuramoylalanine D-glutamate ligase (MurD ligase). Due to different biological activities, numerous methods for the synthesis of thiazolidinedione derivatives have been developed. Many methods for the synthesis of these compounds are conventional and are not environmentally acceptable due to utilization of various catalysts and organic solvents. In order to reduce the formation of harmful substances during the synthesis, deep eutectic solvents can be used. Deep eutectic solvents are considered green solvents according to their properties like low toxicity, low inflammability, high recyclability and low volatility. The aim of this work was to synthesize thiazolidinedione derivatives by an environmentally acceptable method. Thiazolidinediones were obtained via Knoevenagel condensation in deep eutectic solvent (choline chloride:N-methylurea) at 80 °C in reactions between substituted benzaldehydes and thiazolidine-2, 4-dione. Synthesized thiazolidinediones are obtained in yields from 21.49 % to 90.90 % and compounds showed lipoxygenase inhibition in the range from 7.7 % to 76.3 %. more...
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- 2021
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28. Characterization of lipases from Burkholderia cepacia and Pseudomonas fluorescens
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Ostojčić, Marta, Budžaki, Sandra, Strelec, Ivica, and Drenjančević, Ines
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lipase , pH optimum ,temperature optimum ,substrate specificity ,kinetics parameters - Abstract
Lipases (EC 3.1.1.3.), triacylglycerol acylhydrolases, are enzymes that, in addition to the triacylglycerol hydrolysis reaction, successfully catalyse the reactions of esterification, interesterification, transesterification, acidolysis and aminolysis, under appropriate reaction conditions. According to the literature, lipases are very active in a wide pH and temperature range, and hydrolyse differently toward different substrates, depending primarily on the microorganism from which they originate. The aim of this research was to characterize lipases from bacteria Burkholderia cepacia (BCL) and Pseudomonas fluorescens (PFL). Using a titrimetric test for lipase activity, with olive oil as a substrate, the linearity of the test reaction, kinetics parameters, and the pH and temperature optimum for each lipase were determined. In addition, the substrate specificity of lipases according to selected commercially available, cold-pressed and waste oils was examined. The results showed that the steady state of the enzymatic hydrolysis of triacylglycerol for both lipases lasted up to 30 min. Lipases optimally hydrolysed olive oil as substrate at pH 8 and temperature of 50 °C. Analysis of experimental data in GraphPad Prism 8 revealed that both enzymes do not follow Michaelis-Menten kinetics, but obey allostery. Allosteric kinetic parameters for BCL were Vmax=16.45 U mL-1, K0.5=32.29 mmol L-1 and h=1.653, and for PFL Vmax=11.97 U mL-1, K0.5=22.92 mmol L-1 and h=1.262. It was found that both lipases have the highest specificity for commercially available oils. All the obtained data will be used for further characterization of lipases as well as for setting initial conditions of their immobilization on appropriate carriers. more...
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- 2021
29. Proximate Analysis of Selected Agro-Food Industrial Wastes: Eggshells, Spent Coffee Grounds and Brown Onion Skins
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Kovačević, Andreja, Ostojčić, Marta, Šereš, Zita, Maravić, Nikola, Strelec, Ivica, Budžaki, Sandra, Babić, Jurislav, Šubarić, Drago, and Jašić, Midhat
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eggshells ,spent coffee grounds ,brown onion skins ,chemical composition ,value added products - Abstract
The agro-food industry generates a vast amount of residues (wastes) every year due to its own constant growth as a number of population is in increasing. Food loss and industry food waste has become an issue of great public concern. Among many types of food wastes eggshells, spent coffee grounds and brown onion skins stand out by their low reusability. Most of these wastes end up in the environment, which is a devastating fact since, according to literature-available data on chemical composition represent high-value material that can be used as secondary feedstock. The eggshells is rich in calcium, while spent coffee grounds and brown onion skins have high content of cellulose, hemicellulose, and valuable bioactive components. The aim of this work was to evaluate the chemical composition of these agro-industrial wastes and point out their possible utilization in vary industries for production of different value added products and eventually as a potential candidates for biorafinery concept. more...
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- 2021
30. Inhibition of α-glucosidase by polyphenols present in traditional apples varieties
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Ištuk, Jozo, Jakobek, Lidija, Strelec Ivica, Jukić, Ante, Ocelić Bulatović, Vesna, Kučić Grgić, Dajana, Ocelić, Bulatović, Vesna, and Kučić, Grgić, Dajana
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α-glucosidase ,inhibition ,polyphenols ,apple ,food and beverages - Abstract
This work aimed to evaluate polyphenols from two traditional apple varieties as a-glucosidase inhibitors. Polyphenols were extracted from the flesh and skin of two traditional apple varieties ('Božićnica' and 'Batulenka') by using ultrasonic- assisted extraction. Total polyphenols in extracts were determined by the spectrophotometric Folin- Ciocalteu method, expressed as gallic acid equivalents (GAE). The α- glucosidase activity was evaluated based on the spectrophotometric determination of p- nitrophenol (pNP) released from p-nitrophenylα-D- glucopyranoside (p-NPG) substrate by the action of the enzyme. To inhibit enzyme activity, various polyphenol concentrations were added to the reaction mixture. IC50 value was calculated (concentration of polyphenols that gives 50 % inhibition). 'Božićnica' and 'Batulenka' contained 337.24 and 202.17 mg GAE/kg in the flesh and 2132.91 and 824.43 mg GAE/kg in the peel, respectively. Polyphenols inhibited a- glucosidase activity and inhibition reached a steady state. IC50 values, expressed as µg of gallic acid equivalents (GAE) per mL of reaction solution, of the flesh of 'Batulenka' and 'Božićnica' were 1.69 and 1.47, respectively. Peel showed similar IC50 values (1.07, and 0.33 μg GAE/mL, for the peel of 'Batulenka' and 'Božićnica', respectively). These results suggest that polyphenols from the flesh and skin of traditional apple varieties are potent inhibitors of α-glucosidase activity more...
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- 2021
31. Inhibition of α-amylase by polyphenols present in the peel of traditional, indigenous apple varieties
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Ištuk, Jozo, Matić, Petra, Tomac, Ivana, Strelec, Ivica, Jakobek, Lidija, Rozman, Vlatka, and Antunović, Zvonko
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apple varieties ,traditional ,inhibition ,α-amylase - Abstract
The aim of this work was to evaluate polyphenols from the peel of two traditional apple varieties as α-amylase inhibitors. The extraction of polyphenols from the peel of two traditional apple varieties (Citronka and Kolačara) was conducted using 80% methanol as a solvent with the help of an ultrasonic bath. The main polyphenol subgroups (dihydrochalcones, flavanols, flavonols, and phenolic acids) found in extracts were separated using gel chromatography. Three fractions were collected for each apple variety and analyzed using reversed-phase high-performance liquid chromatography (RP-HPLC). The α-amylase activity was evaluated based on the spectrophotometric determination of maltose released from starch by the action of the enzyme. To inhibit enzyme activity, various concentrations of fractions were added to the reaction mixture. IC50 values were calculated (concentration of polyphenols that gives 50 % inhibition). Fraction 1 was mainly composed of flavanols (94 % and 100 %), fraction 2 was rich in dihydrochalcones and phenols acids (69 % and 54 %) while fraction 3 was predominantly made of flavonols (92 % and 64 %) for Citronka and Kolačara, respectively. All the fractions showed inhibition capacity with IC50 values ranging from 0.54 μg/mL (fraction 1 of Citronka) to 40.01 μg/mL (fraction 3 of Citronka). The results suggest that polyphenols from the peel of traditional, indigenous apple varieties are potent inhibitors of α-amylase activity. more...
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- 2021
32. Imobilizacija lipaza na funkcionalizirane nosače na bazi odabranih otpada iz poljoprivredno- prehrambene industrije
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Budžaki, Sandra, Strelec, Ivica, Ostojčić, Marta, Velić, Natalija, Stjepanović, Marija, Bilić Rajs, Blanka, Šereš, Zita, Maravić, Nikola, Stanojev, Jovana, Hessel, Volker, and Miličević, Borislav
- Subjects
lipaze ,imobilizacija ,otpad poljoprivredno-prehrambene industrije - Abstract
Lipaze, triacilglicerol-acilhidrolaze, su zbog svoje svestranosti djelovanja našle primjenu u prehrambenoj industriji, industriji kože i tekstila, ulja i masti, papira te u kozmetičkoj i farmaceutskoj industriji. Iako je primjena lipaza u odnosu na kemijske katalizatore poželjnija, zbog visoke specifičnosti obzirom na supstrat i tip reakcije, ekološku prihvatljivost i energetsku nezahtjevnost, visoka cijena lipaza kao i vrlo česta nemogućnost ponovne uporabe slobodnih lipaza predstavlja ključnu prepreku za širu primjenu u industrijskoj proizvodnji. Navedeno se može nadići primjenom imobiliziranih lipaza, koje se po završenom proizvodnom procesu mogu lako izdvojiti iz reakcijske smjese te ponovo uporabiti u sljedećem proizvodnom procesu ili u kontinuiranim procesima proizvodnje. Za imobilizaciju enzima danas se koriste različite tehnike koje se mogu svrstati u tri osnovne skupine: i) imobilizaciju adsorpcijom, ii) imobilizaciju direktnim ili indirektnim kovalentnim vezanjem, te iii) imobilizaciju zarobljavanjem enzima. Obzirom da većina komercijalno dostupnih nosača ima relativno visoku cijenu, postoji potreba za pronalaskom jeftinijih. Među brojnim otpadom poljoprivredno- prehrambene industrije kao potencijalni kandidati za proizvodnju nosača izdvajaju se ljuska jaja, talog kave i ljuska crvenog luka koji još nisu pronašli odgovarajuće mjesto u održivoj proizvodnji, nego se uglavnom odlažu na polja i odlagališta te na takav način dodatno opterećuju okoliš. Primjenom inovativnih tehnika transformacije otpada mogli bi se proizvesti nosači na bazi celuloze i/ili hemiceluloze (talog kave i ljuska crvenog luka) ili nosači na bazi kolagenske mreže (membrana ljuske jaja). Za očekivati je da će se u sljedećih nekoliko desetljeća morati pronaći nove i/ili poboljšati postojeće tehnologije koje će slijediti trend održive proizvodnje obzirom na porast interesa za proizvodima koji su dobiveni na zdrav i održiv način. more...
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- 2021
33. Preparation of Multifunctional N-Doped Carbon Quantum Dots from Citrus clementina Peel: Investigating Targeted Pharmacological Activities and the Potential Application for Fe3+ Sensing
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Šafranko, Silvija, primary, Stanković, Anamarija, additional, Hajra, Sugato, additional, Kim, Hoe-Joon, additional, Strelec, Ivica, additional, Dutour-Sikirić, Maja, additional, Weber, Igor, additional, Bosnar, Maja Herak, additional, Grbčić, Petra, additional, Pavelić, Sandra Kraljević, additional, Széchenyi, Aleksandar, additional, Mishra, Yogendra Kumar, additional, Jerković, Igor, additional, and Jokić, Stela, additional more...
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- 2021
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34. Correction to: Characterization of Croatian Honeys by Right-Angle Fluorescence Spectroscopy and Chemometrics
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Strelec, Ivica, Brodar, Lidija, Flanjak, Ivana, Čačić Kenjerić, Frane, Kovač, Tihomir, Čačić Kenjerić, Daniela, and Primorac, Ljiljana
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- 2017
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35. Lipoxygenase Inhibition by Plant Extracts
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Lončarić, Melita, primary, Strelec, Ivica, additional, Moslavac, Tihomir, additional, Šubarić, Drago, additional, Pavić, Valentina, additional, and Molnar, Maja, additional
- Published
- 2021
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36. Comparison of colorimetric and spectrophotometric methods for colour determination in pasta
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Ugarčić-Hardi, Ž., Perić, Ljiljana, Strelec, Ivica, and Koceva, Daliborka
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- 1999
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37. Production of biodiesel byBurkholderia cepacialipase as a function of process parameters
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Ostojčić, Marta, primary, Budžaki, Sandra, additional, Flanjak, Ivana, additional, Bilić Rajs, Blanka, additional, Barišić, Iva, additional, Tran, Nghiep Nam, additional, Hessel, Volker, additional, and Strelec, Ivica, additional more...
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- 2020
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38. Lipoxygenase Inhibition Activity of Coumarin Derivatives—QSAR and Molecular Docking Study
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Lončarić, Melita, primary, Strelec, Ivica, additional, Pavić, Valentina, additional, Šubarić, Domagoj, additional, Rastija, Vesna, additional, and Molnar, Maja, additional
- Published
- 2020
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39. Wheat dough rheology and bread quality effected by Lactobacillus brevis preferment, dry sourdough and lactic acid addition
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Komlenić, Daliborka Koceva, Ugarčić-Hardi, Žaneta, Jukić, Marko, Planinić, Mirela, Bucić-Kojić, Ana, and Strelec, Ivica
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- 2010
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40. Antibacterial activity of chestnut honey (Castanea sativa Mill.) against Helicobacter pylori and correlation to its antioxidant capacity
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Cviljević, Sabina, Bilić Rajs, Blanka, Primorac, Ljiljana, Strelec, Ivica, Gal, Katarina, Cvijetić Stokanović, Milica, Penava, Ariana, Mindum, Anita, and Flanjak, Ivana
- Subjects
chestnut honey ,Helicobacter pylori ,antibacterial activity ,antioxidant capacity ,digestive, oral, and skin physiology ,food and beverages - Abstract
One of the proven therapeutic properties of honey is its antimicrobial activity. The aim of this study was to examine the antimicrobial activity of chestnut honey against Helicobacter pylori and to evaluate a relationship between the content of phenols, antioxidant capacity and antimicrobial activity. The antimicrobial activity of honey was determined by the agar well diffusion method, and the inhibitory effect of different honey concentrations (20%, 50% and 75%) was evaluated. The phenolic content was determined by the Folin- Ciocalteu method while the total antioxidant capacity was determined by the FRAP assay. Water activity and hydrogen peroxide content were also determined. The results showed that the zones of inhibition of H. pylori ranged from eight to 21 mm depending on the sample and the concentration of honey, where the concentration of honey of 20% did not have inhibitory effect. The phenolic content ranged from 204.94 to 233.82 mg of GA/kg while FRAP values were between 392.71 and 441.53 μM Fe (II). The honey sample that showed the highest antimicrobial activity against H. pylori also had the highest total antioxidant capacity. However, the same correlation was not observed in the other analysed samples. Further research is needed to determine the contribution of individual components of honey to its antimicrobial activity. more...
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- 2020
41. Proizvodni ostaci poljoprivredno-prehrambene industrije kao baza za održivu proizvodnju biodizela
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Budžaki, Sandra, Ostojčić, Marta, Strelec, Ivica, and Ačkar, Đurđica
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proizvodni ostaci poljoprivredno-prehrambene industrije ,otpadna ulja i masti ,lipaze ,heterogeni biokatalizatori ,biodizel - Abstract
Zbog svoje biorazgradivosti i netoksičnosti biodizel se smatra zelenim gorivom. Međutim, obzirom na trenutačnu tehnologiju na razini industrijske proizvodnje koja se temelji na homogenoj kemijskoj katalizi, biodizel nije tako zelen kako se čini. S jedne strane, korištenjem biodizela, smanjuje se emisija štetnih plinova u atmosferu, prvenstveno CO2, dok se s druge strane troše velike količine energije za proizvodnju takvog biogoriva. Nadalje, generiraju se velike količine otpadne vode koju je potrebno dalje zbrinuti što uvelike poskupljuje proizvodnju biodizela i njegovu konačnu cijenu te smanjuje konkurentnost na tržištu. Trenutačna proizvodnja biodizela može se učiniti održivom pa time i zelenijom i ekološki prihvatljivijom ne samo uvođenjem biokatalizatora u postojeću ili novu tehnologiju proizvodnje, već i uvođenjem alternativnih sirovina, poput proizvodnih ostataka poljoprivredno-prehrambene industrije u pojedine faze tehnološkog procesa proizvodnje. Već su značajni rezultati zabilježeni korištenjem nejestivih i otpadnih ulja i masti te uljnih frakcija kao jeftinijih sirovina čime je skinuta etička sumnja s biodizela koja se temelji na pretvorbi hrane (jestivih ulja) u (bio)gorivo. Najveći nedostaci proizvodnje biodizela enzimskom katalizom (homogenim ili heterogenim biokatalizatorima) su visoka cijena komercijalno dostupnih lipaza i nosača za imobilizaciju te razlog što još uvijek nije prenesena u industrijsko mjerilo. Proizvodnja biodizela iz proizvodnih ostataka poljoprivredno-prehrambene industrije koji je komplesknog sastava, široko dostupan i jeftin te uvelike opterećuje okoliš, trenutačno predstavlja veliki izazov. Iskorištavanjem energije zaostale u biološkom materijalu koji je već prošao ciklus prerade i klasificiran kao otpad/nusproizvod, potencijalno se snižava cijena gotovih proizvoda dobivenih na zdrav i siguran način putem biokatalitičkih procesa. Biokatalitički procesi najčešće ostavljaju jedva primjetan ekološki otisak u odnosu na kemijski katalizirane procese, a ekološki su prihvatljiviji te više u skladu s načelima održivog razvoja. Povrh navedenog stvara se dodana vrijednost porizvodnim ostacima poljoprivredno-prehrambene industrije što je jedan od temelja kružnog gospodarenja. Lipaze imobilizirane na otpad poljoprivredno-prehrambene industrije predstavljaju tehnološko i ekonomsko poboljšanje biokatalitičke proizvodnje koje jasno upućuje na mogućnost ostvarivanja održive proizvodnje na temelju kružnog gospodarenja i približavanja „zero-waste“ modelu. more...
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- 2020
42. Extraction and separation of polyphenol classes in chokeberry and elderberry fruit
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Ištuk, Jozo, Jakobek, Lidija, Strelec, Ivica, and Jukić, Ante
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food and beverages ,berries ,polyphenols ,extraction ,separation - Abstract
Chokeberry (Aronia melanocarpa) and elderberry (Sambucus nigra L.) fruits are one of the richest dietary sources of polyphenols, a natural bioactive compounds. Anthocyanins are the most prevalent polyphenols in these fruits although other classes such as phenolic acids, flavonols, and flavanols are present as well. Those phenolic subgroups can show different bioactivities. That is why it can often be apropriate to examine bioactivities of these subgroups separately. The aim of this study was to to extract and determine polyphenols from chokeberry and elderberry and to separate polyphenol subgroups present in the extracts. The extraction was conducted using 80 % methanol as a solvent with the help of ultrasonic bath, and repeating the extraction step four times. Polyphenol subgroups found in extracts were separated using gel chromatography fractionation with Sephadex LH-20 as a stationary phase and different percentages of methanol in water as a mobile phase. Polyphenols in extracts and fractions were analysed using reversed-phase high performance liquid chromatography (RP- HPLC). The amount of polyphenols extracted from chokeberries and elderberries was 15557 and 10009 mg kg-1 of fresh fruit weight, respectively. Four fractions were separated for each fruit. Flavanols were eluted in fraction 1 (100 % and 100 %) and phenolic acids in fraction 2 (100 % and 100 %), anthocyanins were dominant in fraction 3 (91 % and 55 %), while flavonols were prevalent in fraction 4 (53 % and 100 %) for chokeberry and elderberry, respectively. Using gel-chromatography fractionation, four fractions containg different polyphenol subgroups were seeparated which could be useful in further research. more...
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- 2020
43. Potencijal ljuske jaja za proizvodnju visokovrijednih proizvoda
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Strelec, Ivica, Ostojčić, Marta, Budžaki, Sandra, and Ačkar, Đurđica
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ljuska jaja ,kalcijeve soli ,membrana jaja ,proteini ,lizozim - Abstract
Jedan od pet glavnih izazova održivog gospodarenja otpadom poljoprivredno-prehrambene industrije je primjena strategije kružnog gospodarenja po modelu „zero-waste“ uz razvoj inovativnih tehnika transformacije otpada u svrhu proizvodnje visokovrijednih proizvoda poput kemikalija, dodataka prehrani, farmaceutika, nutraceutika i/ili funkcionalnih materijala. Među brojnim otpadom ističe se i ljuska jaja koja bi mogla poslužiti kao sirovina za proizvodnju najmanje tri različite klase visokovrijednih proizvoda: antimikrobnih proteina, kalcijevih soli, te nosača za imobilizaciju enzima. Može li se ljuska jaja kao otpad iskoristiti za istovremenu proizvodnju istih je pitanje na koje se ovim istraživanjem htio dobiti odgovor. U tu svrhu, ljuska jaja je podvrgnuta dvostupanjskoj obradi. U prvom stupnju obrade, ispiranjem ljuske jaja vodom, u otopini su dobiveni visokovrijedni proteini bjelanjka, a među inima i antimikrobni enzim lizozim, pri čemu je na 10 g vlažne mase ljuske jaja dobiveno 142 ± 2, 81 mg proteina, dok je lizozim pokazao prosječnu aktivnost od 300 ± 10 U/mL, odnosno ekvivalent od 30680 U po 10 g ljuske jaja. U drugom stupnju obrade ljuske jaja vodenim otopinama octene, kloridne ili o-fosforne kiseline provedeno je potpuno otapanje kalcijeva karbonata ljuske jaja te su istovremeno dobivene otopine odgovarajućih kalcijevih soli (kalcijev klorid, kalcijev acetat, kalcijev hidrogenfosfat) i membrane jaja kao potencijalni nosači za imobilizaciju enzima. Prosječni prinos membrana jaja iznosio je 0, 25 ± 0, 1 g na 10 g vlažne mase ljuske jaja, a primjenom postupaka uparavanja i taloženja etanolom, kalcijeve soli su izdvojene iz otopina u obliku kristala i/ili praha uz visoki stupanj prinosa (< 90%). Mogu li se dobivene kalcijeve soli uporabiti kao aditivi u prehrambenoj industriji i/ili kao dodatci prehrani pokazat će daljnje analize. more...
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- 2020
44. Inhibition of alfa-glucosidase by polyphenols present in traditional, indigenous apple varieties
- Author
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Ištuk, Jozo, Jakobek, Lidija, Strelec, Ivica, and Jukić, Ante
- Subjects
α-glucosidase ,inbition ,polyphenols ,apple ,food and beverages - Abstract
This work aimed to evaluate polyphenols from two traditional apple varieties as - glucosidase inhibitors. Polyphenols were extracted from the flesh and skin of two traditional apple varieties (Božićnica and Batulenka) by using ultrasonic- assisted extraction. Total polyphenols in extracts were determined by the spectrophotometric Folin- Ciocalteu method, expressed as gallic acid equivalents (GAE). The α-glucosidase activity was evaluated based on the spectrophotometric determination of p-nitrophenol (pNP) released from pnitrophenyl-α-D-glucopyranoside (p-NPG) substrate by the action of the enzyme. To inhibit enzyme activity, various polyphenol concentrations were added into the reaction mixture. IC50 value was calculated (concentration of polyphenols that gives 50% inhibition). Božićnica and Batulenka contained 337.24 and 202.17 mg GAE kg-1 in the flesh and 2132.91 and 824.43 mg GAE kg-1 in the peel, respectively. Polyphenols inhibited - glucosidase activity and inhibition reached a steady state. IC50 values, expressed as μg of gallic acid equivalents (GAE) per mL of reaction solution, of the flesh of Batulenka and Božićnica were 1.69 and 1.47, respectively. Peel showed similar IC50 values (1.07, and 0.33 μg GAE cm-3, for the peel of Batulenka and Božićnica, respectively). These results suggest that polyphenols from the flesh and skin of traditional apple varieties are potent inhibitors of α- glucosidase activity. more...
- Published
- 2020
45. Application of lipase in food industry
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Budžaki, Sandra, Ostojčić, Marta, Kovačević, Andreja, Strelec, Ivica, Babić, Jurislav, Šubarić, Drago, Jašić, Midhat, and Jozinović, Antun
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digestive, oral, and skin physiology ,food and beverages ,lipase ,food industry ,food supplements - Abstract
Lipases are versatile biocatalysts that besides hydrolysis of triacylglycerols, catalyse the reactions of esterification, interesterification, acidolysis and aminolysis under suitable reaction conditions. Due to their versatility, lipases have been widely used in the industry of leather and textile, oil and grease, paper and cosmetic, and also in pharmaceutical and food. Lipases are used in free form as an active supplement to food products such as bakery and pasta, cheeses and dairy products, which affect the quality and flavour enhancement of the final product, or in immobilized form they are used in production of substitutes for human milk and cocoa butter, for the production of specific flavours as food additives, or for the production of omega-3 and omega-6 fatty acids from fish and other oils. While the share of lipases in current industrial production is about 10% of all industrial enzymes, it is expected that their use will be increased due to their versatility. The aim of this paper is to give overview of the current knowledge of industrial use of lipases in the food industry, both as an integral part of the product, and as biocatalysts to obtain food products or alternatives for certain products that can be used as a food or food supplements. more...
- Published
- 2019
46. Hydrogen peroxide content and glucose oxidase activity of honeys
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Strelec, Ivica, Flanjak, Ivana, Primorac, Ljiljana, Katalinić, Maja, Dulić, Morana, and Stuparević, Igor
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honey ,hydrogen peroxide ,glucose oxidase ,digestive, oral, and skin physiology ,food and beverages - Abstract
Hydrogen peroxide (H2O2) accumulation in honey occurs upon honey dilution due to the action of reactivated glucose oxidase (GOX) which oxidize glucose to gluconic acid, simultaneously liberating H2O2 as by-product. Although the presence of GOX in honey seems necessary for H2O2 evolution, there is no report on the correlation between GOX activity and H2O2 content in diluted honeys, so far. Besides numerous factors that may affect GOX activity and H2O2 content, one of the possible reason for the lack of correlation might be a difference in methods and conditions used for their determination. Namely, H2O2 content is measured in diluted honeys (realistic conditions) by various methods, while GOX activity of honey mostly in the model solution of 1.5 M glucose as substrate by standard o-dianisidine/HRP method (artificial conditions). In order to test whether the difference in determination methods might be a reason for the lack of correlation, we have determined GOX activity and H2O2 content in 15 different samples of honey at five different mass to volume ratios (1:1 ; 1:2 ; 1:4 ; 1:8 ; 1:16) using o-dianisidine/HRP method. For measurement of GOX activity, HRP and o-dianisidine were added to diluted honey prior to 30 minute incubation, while for H2O2 content at the end of incubation period. In addition, sugar profile of honeys, GOX activity in model solutions of glucose or mixture of glucose and fructose equal to their concentrations in diluted honeys, as well as water activity of diluted honeys and model solutions were determined. GOX activity curves followed the curves of H2O2 accumulation in diluted honeys, indicating applicability of o-dianisidine/HRP method for simultaneous determination of GOX activity and H2O2 content. Similarity of curves was confirmed by relatively high coefficients of correlation ranging from 0.853 for the lowest, up to 0.971 for highest dilution. However, GOX activities in model solutions of glucose or glucose and fructose at concentrations equal to those in diluted honeys were found quite higher. On the basis of water activity determination, it seems that both, GOX activity and H2O2 accumulation in honeys are affected by macromolecular crowding milieu of honey biomolecules. more...
- Published
- 2019
47. Weight Loss Biochemistry
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Strelec, Ivica, Sokolić, Darja, Babić, Jurislav, Šubarić, Drago, and Jašić, Midhat
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biochemistry ,diets ,obesity ,owerweight ,weight loss - Abstract
Through the evolution human body has been programed to store the excess of energy in two different pools, glycogen and triacylglicerols. While the first one is less prone to the changes in the evolutionary programmed storage capability, the latter one has almost unlimited capability to be stored, not only to the evolutionary created safe storage “warehouse” (adipocytes), but also to other cells of the human body when fatty acid spillover occurs. While this evolutionary inheritance worked more or less well during the ages, where the excess of available foods has been stored in metabolic pools in periods of food abundance, and than used for energy input in times of food shortages, the development of modern human societies, characterized with the high level of industrialization and automatization led to the disruption of this equilibrium toward the former one. Nowadays, modern human societies has been challenged with the continuous excess of available foods and decreased physical activity, what subsequently leads to the increased level of overweight and obesity among population. Therefore, the need for social programming of human societies toward healthy lifestyle, including increase in physical activity and changes in dietary habits, is inevitable. In this respect, the present lecture will give overview of the current knowledge of the effect of physical activity, oftenly used reduction diets, and their combined effects on weight loss from the biochemical point of view. more...
- Published
- 2019
48. Biocatalytic biodiesel synthesis with Burkholderia cepacia and Pseudomonas fluorescens lipase
- Author
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Budžaki, Sandra, Ostojčić, Marta, Strelec, Ivica, Vidović, Senka, Jovicic, Mirjana, Popovic, Ljiljana, Sumic, Zdravko, Hadnadjev, Milica, Govedarica, Olga, Vucetic, Snezana, and Bera, Oskar
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lipase ,biodiesel ,Burkholderia cepacia ,Pseudomonas fluorescens ,food and beverages ,complex mixtures - Abstract
Biodiesel is a mixture of fatty acid methyl esters, usually produced by a transesterification reactions in the presence of sodium hydroxide as catalyst. However, this most often used industrial process for biodiesel synthesis has certain shortcomings. Thus, the use of new catalysts, and among them biocatalyst such as lipases are preferred. Lipases (EC 3.1.1.3.), triacylglycerol acylhydrolases, are enzymes of plant, animal or microbial origin, which are capable to perform efficient transesterification reactions in the presence of organic solvents. Although the use of lipases in biodiesel synthesis is well documented, there are few questions which still need to be resolved, and among it optimal conditions for biodiesel biocatalytic production. Namely, various temperatures and pH’s could be found reported for biodiesel production, which are in some instances different from optimal temperature and pH of lipases used in transesterification reaction. Moreover, determination of pH and temperature optimum for lipase activity has been performed by various substrates differing in their chemical structure and composition, which additionally complicates selection of optimal conditions. Therefore, the aim of this study was to determine pH and temperature optimum of Burkholderia cepacia and Pseudomonas fluorescens lipases using two chemically and structurally different substrates: olive oil and p-nitrophenyl palmitate, and to examine efficiency of biodiesel biocatalytic synthesis in batch reactor at determined optimal conditions for lipase activity. Results have shown that optimal conditions (pH and temperature) for lipase activity are differing regarding substrate used, and that those determined by olive oil are well in accordance with data obtained from manufacturer. Furthermore, during batch reactor biodiesel synthesis, greater amount of fatty acid methyl esters (FAME) were produced at optimal conditions determined with olive oil as lipase substrate, than with p-nitrophenyl palmitate. Data on the percentage of FAME in crude biodiesel has shown that Burkholderia cepacia lipase is more suitable for biodiesel synthesis, where more than 96.5% FAME were obtained after 24 hours of synthesis, in comparison to Pseudomonas fluorescens lipase with maximally 71.9% of FAME produced at optimal conditions. Obtained data indicates that greater amount of biodiesel can be produced if optimal conditions for lipase activity (pH and temperature optimum) are applied during batch reactor synthesis. However, optimal conditions for lipase activity should be determined with olive oil test as more reliable. more...
- Published
- 2019
49. Synthesis, Tyrosinase Inhibiting Activity and Molecular Docking of Fluorinated Pyrazole Aldehydes as Phosphodiesterase Inhibitors
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Rastija, Vesna, primary, Brahmbhatt, Harshad, additional, Molnar, Maja, additional, Lončarić, Melita, additional, Strelec, Ivica, additional, Komar, Mario, additional, and Pavić, Valentina, additional more...
- Published
- 2019
- Full Text
- View/download PDF
50. AFLATOXIGENIC EFFECT OF ILLUMINATED FULLERENE NANOPARTICLES
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Kovač, Tihomir, Šarkanj, Bojan, Klapec, Tomislav, Borišev, Ivana, Kovač, Marija, Nevistić, Ante, Strelec, Ivica, Jozinović, Antun, Budžaki, Sandra, and Strelec, Ivica
- Subjects
food and beverages ,fullerene C60 nanoparticles ,VIS illumination ,Aspergillus flavus NRRL 3251 ,aflatoxin B1 ,oxidative stress - Abstract
This study examined the effect of environmentally plausible fullerene C60 nanoparticle (nC60) concentrations on the aflatoxigenic fungi Aspergillus flavus NRRL 3251. Fungi were grown in YES medium for 168 h at 29 °C in the presence of 0, 10, 50 and 100 ng mL-1 of nC60 under VIS illumination (LED bulb, 50 W, 2250 Lux, Stella) in the 12 h light/12 h dark regime. Dry mycelial weight measurement was used for the antifungal activity estimation, while an effect of nC60 on aflatoxin production in YES media was assessed using a dilute and shoot LC-MS/MS method. Additionally, the main oxidative status markers of A. flavus cell (TBARS, GSH/GSSG ratio, Cu, Zn-SOD, Mn-SOD, and CAT) were determined by standard biochemical assays. Fullerene C60 nanoparticles caused a slight increase in the mycelial growth, but significantly boosted aflatoxin B1 production up to 8 times the control values at 10 ng mL-1 of nC60. Oxidative status markers indicated that aflatoxigenic effect of the illuminated C60 nanoparticles could be attributed to their strong prooxidant action on A. flavus. These results imply negative consequences of the increased release and environmental occurrence of fullerene C60. more...
- Published
- 2017
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