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1.
Properties of Mint as a Food Preservative
Rok Penko, 2011, undergraduate thesis

Abstract: This study was designed to evaluate antimicrobial and antioxidant activities of the mint extracts from Mentha piperita L. and Mentha aquatica L. In vitro antibacterial activity against two foodborne bacteria (Listeria monocytogenes, Staphylococcus aureus) was evaluated by the well diffusion method. The activity was assessed by the diameter of the inhibition zone. Four of the five extracts from Mentha piperita were active against S. aureus, but none of the extracts was active against L. monocytogenes. Extracts obtained from Mentha aquatica showed no activity against both foodborne bacteria. The horseradish peroxidase/guaiacol assay was used to investigate in vitro antioxidant activity of two mint extracts (Mentha piperita and Mentha aquatica). The ascorbic acid was tested as a reference compound with known antioxidant activity to validate our approach. Extracts from Mentha aquatica showed strong antioxidant activity, but on the other hand, extracts from Mentha piperita showed no antioxidant activity.
Keywords: preservatives, Listeria monocytogenes, Staphylococcus aureus, antimicrobial activity, antioxidant activity, mint extracts
Published: 21.04.2011; Views: 1933; Downloads: 86
.pdf Full text (1,10 MB)

2.
Enzymatic synthesis of sugar fatty acid esters in organic solvent and in supercritical carbon dioxide and their antimicrobial activity
Maja Leitgeb, Saša Šabeder, Željko Knez, 2008, original scientific article

Abstract: Lipase-catalyzed synthesis of different sugar fatty acid esters was performed in high yields in 2-methyl-2-butanol at atmospheric pressure and in supercritical carbon dioxide (SC CO2) at 10 MPa. Influence of molecular sievesconcentration on conversion in SC CO2 was studied. Growth inhibitory effect of commercial sucrose fatty acid esters and enzymatically synthesized sucrose and fructose fatty acid esters on Gram-positive and Gram-negative micro-organisms, as well as on yeast was tested. Sucrose laurate inhibited the growth of Bacillus cereus food poisoning bacteria at a concentration of 9.375 mg/ml.
Keywords: biocatalysis, lipase, sugar fatty acid ester, organic solvent, cupercritical CO2, antimicrobial activity
Published: 31.05.2012; Views: 1307; Downloads: 68
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3.
Adsorption and antibacterial activity of soluble and precipitated chitosan on cellulose viscose fibers
Lidija Fras Zemljič, Tijana Ristić, Tina Tkavc, 2012, original scientific article

Abstract: The aim and novelty of this work was to compare the adsorption of totally-soluble chitosan (acidic solution) against the adsorption of precipitated chitosan, onto cellulose fibers. The influences of both these chitosan-adsorption procedures on a final amino groupćs content in functionalized cellulose fibers were studied, using potentiometric titration and the conventional spectrophotometric C.I. Acid Orange 7 method. Surface modification and adsorption of chitosan were, in addition, monitored by determining XPS spectra. The antimicrobial activities of both chitosan- functionalised cellulose fibers were examined, in regard to pathogen bacteria and fungus.
Keywords: functionalized viscose, chitosan solution, precipitates, potentiometric titration, spectrophotometry, antimicrobial activity
Published: 01.06.2012; Views: 1364; Downloads: 226
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4.
Antimicrobial medical textiles based on chitosan nanoparticles for gynaecological treatment
Tijana Ristić, 2014, doctoral dissertation

Abstract: The aim of this dissertation was to develop a novel medical tampon for alternative gynaecological treatment using chitosan nanoparticles as an antimicrobial agent or as a drug delivery system. For this purpose viscose tampon band was used and functionalized with chitosan and trimethyl chitosan nanoparticles. A comprehensive of interactions between chitosan and cellulose as well as characterization of prepared materials were done. At the beginning, chitosan (CS) and trimethyl chitosan (TMC) solutions, as well as nanoparticles synthesised by ionic gelation were studied. Their characterization was focused on determining the charge and antimicrobial properties against common pathogenic microorganism. The influence of cationic charge on the inhibition of microbial growth was confirmed. Since CS and TMC solutions and nanoparticles dispersions exhibited antibacterial activity against Lactobacillus, a detailed investigation in chitosan’s antimicrobial mode of action was performed using a novel diffusion nuclear magnetic resonance (D-NMR). D-NMR allowed the monitoring of intra- and extracellular water exchange from the cells indicating the membrane alteration and leakage of intracellular constituencies. Further, in order to study the adsorption phenomena and molecular interactions between CS/TMC (solution or nanoparticles) and cellulose material, model cellulose surfaces were used, and adsorption was studied by quartz crystal microbalance with dissipation. CS and TMC were favourably deposited onto cellulose model surface at higher ionic strength, higher pH values, i.e. factors causing lower solubility, where the presence of electrostatic interactions was negligible and non-electrostatic interactions were dominant. The knowledge gained from the model surfaces was extremely helpful in characterization of real systems, i.e. functionalized cellulose fibres and for understanding the obtained results. Immobilization of CS and TMC (in the form of solution and/or nanoparticles) onto cellulose viscose fibres was confirmed with several analytical methods. The attachment of chitosan onto fibres was reversible, as endorsed with desorption studies mimicking the conditions of vaginal usage. Evaluation of antimicrobial properties was performed using two different techniques, both revealing a high inhibition of the tested microorganism. In addition, Lactobacillus susceptibility testing has shown that chitosan-coated fibres do not have any negative influence on the resident microbiota. Assessment of in-vitro cytotoxicity demonstrated that samples do not cause a cytotoxic effect in direct contact. Additionally, model drug was incorporated into chitosan nanoparticles and subsequently attached onto fibres in order to create modern, vaginal drug delivery systems. Antimicrobial medical textiles investigated in the scope of this dissertation show the potential for their exploitation in gynaecological field as preventive or curative treatment without triggering any adverse effects for the user.
Keywords: chitosan, N, N, N-trimethyl chitosan, nanoparticles, antimicrobial activity, cellulose model films, regenerated cellulose fibres, diffusion nuclear magnetic resonance, quartz crystal microbalance, vaginal infections, drug delivery systems, cytotoxicity
Published: 13.02.2014; Views: 1981; Downloads: 77
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Antioxidant and antimicrobial activity of PGSStm micronized curcuma powder
Željko Knez, Tina Perko, Mojca Škerget, 2012, published scientific conference contribution

Keywords: antioxidant, antimicrobial activity, curcumin extract
Published: 10.07.2015; Views: 464; Downloads: 12
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7.
Viscose functionalisation with a combination of chitosan/BTCA using microwaves
Olivera Šauperl, Julija Volmajer Valh, 2013, original scientific article

Abstract: Improved hygiene and health care standards have a great impact on the development of hygiene and health care products. For this purpose, viscose is a very popular substrate. One of the most promising anti-microbial compounds of modern times is chitosan. The anti-microbial action of this polysaccharide depends on the amino group amount, which is crucial for ensuring the effectiveness of anti-microbial treated material. In textile finishing, 1,2,3,4-buthanetetracarboxylic acid (BTCA) is usually used as a non-formaldehyde crease-resistant reagent. But, on the other hand, the negatively charged carboxyl groups of BTCA can be explored as additional binding sites for positively-charged protonated amino groups of chitosan. When using microwaves, polar materials (e.g. chitosan) orient and reorient themselves according to the direction of the electro-magnetic field, which means that chitosan chain-bending may have taken place during the drying with microwaves. This could result in a higher specific surface of the chitosan and, consequently, in a higher proportion of available amino groups. It is concluded that the combination chitosan/BTCA supported by microwaves drying represents an ideal combination to increase the proportion of available amino groups.
Keywords: viskoza, protimikrobna zaščita, viscose, chitosan/BTCA, microwawes, Acid Orange VII, methylene blue, antimicrobial activity
Published: 10.07.2015; Views: 663; Downloads: 15
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8.
Effect of peptides' binding on the antimicrobial activity and biocompatibility of ‎protein-based substrates ‎
Maja Kaisersberger Vincek, 2017, doctoral dissertation

Abstract: This work reveals the effect of coupling approach (chemical by using carbodiimide chemistry ‎and grafting-to vs. grafting-from synthesis routes, and enzymatic by using transglutaminase) ‎of a hydrophilic ε-poly-L-lysine (εPL) and an amphiphilic oligo-acyl-lysyl (OAK) derivative (K-7α12-OH) to wool fibers and gelatine (GEL) macromolecules, respectively, and substrates ‎antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus bacteria ‎after 1–24 h of exposure, as well as their cytotoxicity. Different spectroscopic (ultraviolet-‎visible, infrared, fluorescence and electron paramagnetic resonance) and separation ‎techniques (size-exclusion chromatography and capillary zone electrophoresis) as well as ‎zeta potential and potentiometric titration analysis, were performed to confirm the covalent ‎coupling of εPL/OAK, and to determine the amount and orientation of its immobilisation.‎ The highest and kinetically the fastest level of bacterial reduction was achieved with ‎wool/GEL functionalised with εPL/OAK by chemical grafting-to approach. This effect ‎correlated with both the highest grafting yield and conformationally the highly-flexible ‎(brush-like) orientation linkage of εPL/OAK, implicating on the highest amount of accessible ‎amino groups interacting with bacterial membrane. However, OAK`s amphipathic structure, ‎the cationic charge and the hydrophobic moieties, resulted to relatively high reduction of S. ‎aureus for grafting-from and the enzymatic coupling approaches using OAK-functionalised ‎GEL. ‎ The εPL/OAK-functionalised GEL did not induce toxicity in human osteoblast cells, even at ‎‎~25-fold higher concentration than bacterial minimum inhibitory (MIC) concentration of ‎εPL/OAK, supporting their potential usage in biomedical applications.‎ It was also shown that non-ionic surfactant adsorbs strongly onto the wool surface during ‎the process of washing, thereby blocking the functional sites of immobilized εPL and ‎decreases its antibacterial efficiency. ‎ ‎
Keywords: wool, gelatine, antimicrobial peptides, ε-poly-L-lysine, oligo-acyl-lysyl, grafting chemistry, ‎grafting approach, peptide orientation, antibacterial activity, cytotoxicity‎
Published: 17.08.2017; Views: 672; Downloads: 59
.pdf Full text (3,98 MB)

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