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Covalent polymer thin films for biosensor applications
Tina Skorjanc, Andraž Mavrič, Mads Nybo Sorensen, Gregor Mali, Changzhu Wu, Matjaz Valant, 2022, published scientific conference contribution abstract

Keywords: bacteria, sensing, electrochemical impedance spectroscopy, electrophoresis, electrode preparation, Menshutkin reaction
Published in RUNG: 26.09.2022; Views: 651; Downloads: 0
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Novel analytical approaches in quality and safety control in production of fermented beverages : dissertation
Jelena Topić, 2022, doctoral dissertation

Abstract: The exploitation of microorganisms for fermentation goes back centuries. Two types of fermentation are usually used in the winemaking process – alcoholic fermentation and malolactic fermentation. Nowadays, inoculated fermentations with the use of starter cultures are commonly used in order to produce wine with more consistent quality. However, wines can lack in flavour complexity, so scientists and the industry are constantly looking for new and improved starters that can be adapted to different types of wine. In this work we focused on the development and implementation of novel analytical methods for wine quality control. In the course of method development native yeasts and lactic acid bacteria isolates were characterized for wine starter properties. We focused on the determination of biologically active compounds that determine wine quality and safety. Yeasts can influence wine colour through their adsorption capacity and synthesis of stable colour pigments pyranoanthocyanins and lactic acid bacteria can produce biogenic amines which can have adverse detrimental health effects on sensitive consumers when they are present in wines.
Keywords: Saccharomyces yeasts, non-Saccharomyces yeasts, pyranoanthocyanins, thermal-lens spectrometry, lactic acid bacteria, biogenic amines, thin layer chromatography, dissertations
Published in RUNG: 18.02.2022; Views: 1803; Downloads: 98
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Determination of biogenic amines formation by autochthonous lactic acid bacteria from ‘Refošk’ grapes using different analytical methods
Jelena Topić, Lorena Butinar, Martina Bergant Marušič, Dorota Korte, Branka Mozetič Vodopivec, 2022, original scientific article

Abstract: Different analytical methods were tested and optimized for the determination of four biogenic amines (BA) histamine, putrescine, cadaverine and tyramine produced by grape-associated lactic acid bacteria (LAB). Autochthonous LAB were isolated from ‘Refošk’ grapes belonging to Slovenian-Italian Karst region as they represent a potential pool of beneficial LAB starter bacteria for improving the typicality and quality of wine. Six isolated strains were screened by multiplex PCR, of which four strains were positive for BA-forming genes (MKBT-49, MKBT-282, MKBT-568, MKBT-570). The production of BA was evaluated by thin-layer chromatography (TLC), high-performance liquid chromatography coupled to diode array detection (HPLC-DAD) and enzymatic method. The HPLC-DAD results showed that strain MKBT-49 (tyrdc+) had high tyramine production (386.6 ± 0.14 mg/L), which was confirmed by TLC. The ability to produce putrescine was confirmed in strain MKBT-282 by PCR, HPLC-DAD (16.4 ± 1.72 mg/L), and TLC. Histamine-producing ability was detected in strain MKBT-570, with a concentration below the limit of detection of the HPLC-DAD (<0.2 mg/L), while the other two methods were not sensitive enough for confirmation. This study shows that the production of BA can detected in native LAB and that relatively simple method such as TLC can be used effectively for the initial screening.
Keywords: grapes, wine-like matrices, biogenic amines, autochthonous lactic acid bacteria, analytical methods
Published in RUNG: 03.01.2022; Views: 1156; Downloads: 6
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Diversity of bacteria and bacterial products as antibiofilm and antiquorum sensing drugs against pathogenic bacteria
Fazlurrahman Khan, Sandra Oloketuyi, Young-Mog Kim, 2019, review article

Abstract: The increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites. Similarly, non-pathogenic bacteria also take advantages of the QS signaling molecule as a sole carbon source for their growth through catabolism with enzymes. Several enzymes are produced by bacteria which disrupt the biofilm architecture by degrading the composition of extracellular polymeric substances (EPS) such as exopolysaccharide, extracellular- DNA and protein. Thus, the interference of QS system by bacterial metabolic products and enzymatic catalysis, modification of the QS signaling molecules as well as enzymatic disruption of biofilm architecture have been considered as the alternative therapeutic approaches. This review article elaborates on the diversity of different bacterial species with respect to their metabolic products as well as enzymes and their molecular modes of action. The bacterial enzymes and metabolic products will open new and promising perspectives for the development of strategies against the pathogenic bacterial infections.
Keywords: Bacteria, biofilm, quorum sensing, inhibition, metabolites, pathogen, virulence.
Published in RUNG: 18.01.2021; Views: 1858; Downloads: 0
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Treatment strategies targeting persister cell formation in bacterial pathogens
Fazlurrahman Khan, Dung Pham, Nazia Tabassum, Sandra Oloketuyi, Young-Mog Kim, 2020, review article

Abstract: Persister cells are transiently antibiotic-tolerant and dormant subpopulations that are produced to escape the effects of antibiotics within biofilms or planktonic cell populations. Persister cells are of high clinical importance due to their tolerance to antimicrobial agents and subsequent failure in antibiotic treatments. Understanding persister cell formation mechanisms is therefore highly important for developing effective therapeutic strategies against pathogenic bacterial persisters. Several anti-persister compounds have been previously identified via isolation from natural resources or chemical synthesis. Furthermore, a combination of these compounds with antibiotics or non-antibiotic drugs also allows action on multiple targets while reducing the administration frequency. Here, we present a comprehensive overview of the clinical importance and formation mechanisms of persister cells as well as the current treatment strategies against persister cell formations in chronic infections.
Keywords: Biofilm, anti-persister agents, persister cells, pathogenic bacteria, chronic infections
Published in RUNG: 14.01.2021; Views: 1989; Downloads: 0
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Chitosan and their derivatives: Antibiofilm drugs against pathogenic bacteria
Fazlurrahman Khan, Dong Pham, Sandra Oloketuyi, Panchanathan Manivasagan, Junghwan Oh, Young-Mog Kim, 2020, review article

Abstract: Biofilm formed by several pathogenic bacteria results in the development of resistance against antimicrobial compounds. The polymeric materials present in the biofilm architecture hinder the entry of antimicrobial compounds through the surface of bacterial cells which are embedded as well as enclosed beneath the biofilm matrix. Recent and past studies explored the alternative approaches to inhibit the formation of biofilm by different agents isolated from plants, animals, and microbes. Among these agents, chitosan and its derivatives have got more attention due to their properties such as biodegradability, biocompatibility, non-allergenic and non-toxicity. Recent researches have focused on employing chitosan and its derivatives as effective agents to inhibit biofilm formation and attenuate virulence properties by various pathogenic bacteria. Such antibiofilm activity of chitosan and its derivatives can be further enhanced by conjugation with a wide range of bioactive compounds. The present review describes the antibiofilm properties of chitosan and its derivatives against the pathogenic bacteria. This review also summarizes the mechanisms of biofilm inhibition exhibited by these molecules. The knowledge of the antibiofilm activities of chitosan and its derivatives as well as their underlying mechanisms provides essential insights for widening their applications in the future.
Keywords: Antibiofilm, Biofilm inhibition, Chitosan, Chitosan derivatives, Pathogenic bacteria
Published in RUNG: 14.01.2021; Views: 1887; Downloads: 0
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Antibiotics and their different application strategies in controlling the biofilm forming pathogenic bacteria
Fazlurrahman Khan, Dung T N Pham, Sandra Oloketuyi, Young-Mog Kim, 2020, review article

Abstract: Background: The establishment of a biofilm by most pathogenic bacteria has been known as one of the resistance mechanisms against antibiotics. A biofilm is a structural component where the bacterial community adheres to the biotic or abiotic surfaces by the help of Extracellular Polymeric Substances (EPS) produced by bacterial cells. The biofilm matrix possesses the ability to resist several adverse environmental factors, including the effect of antibiotics. Therefore, the resistance of bacterial biofilm-forming cells could be increased up to 1000 times than the planktonic cells, hence requiring a significantly high concentration of antibiotics for treatment. Methods: Up to the present, several methodologies employing antibiotics as an anti-biofilm, antivirulence or quorum quenching agent have been developed for biofilm inhibition and eradication of a pre-formed mature biofilm. Results: Among the anti-biofilm strategies being tested, the sub-minimal inhibitory concentration of several antibiotics either alone or in combination has been shown to inhibit biofilm formation and down-regulate the production of virulence factors. The combinatorial strategies include (1) combination of multiple antibiotics, (2) combination of antibiotics with non-antibiotic agents and (3) loading of antibiotics onto a carrier. Conclusion: The present review paper describes the role of several antibiotics as biofilm inhibitors and also the alternative strategies adopted for applications in eradicating and inhibiting the formation of biofilm by pathogenic bacteria.
Keywords: Antibiotics, biofilm inhibition, multiple antibiotics, pathogenic bacteria, resistance mechanism, virulence factors
Published in RUNG: 14.01.2021; Views: 2040; Downloads: 0
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