>Magister Scientiae - MSc / The high rate of rediscovery of known compounds has led to a decline in the discovery of novel natural products. The high biodiversity of organisms growing in extreme conditions such as oceans has led to the increased interest by researchers for their use as a source of novel natural products. Marine bacteria are known for their extensive biosynthetic capacity to produce diverse natural products, which are suitable for various biotechnology applications such as in agriculture, for treatment of fungal plant pathogens, and as antibiotics, for treatment of bacterial infections. This study aimed at discovering novel secondary metabolites from marine bacteria previously associated with novel marine invertebrate species endemic to the South African coast. The methodologies used in this study included a bioassay guided fractionation coupled to genome sequencing and mining. For the bioassay guided fractionation approach, the study first focused on screening marine bacteria for antimicrobial activity when cultured on 4 different media, against fungal strains previously shown to be virulent olive trunk pathogens. In parallel, the bacterial isolates with the most inhibitory activity against the fungal pathogens were also screened for antimicrobial activity against 4 indicator strains including Gram-negative Escherichia coli 1699 (E. coli), Pseudomonas putida, and Gram-positive Staphylococcus epidermidis ATCC14990, and Bacillus cereus ATCC10702. One of the marine bacterial isolates, PE6-126, showed diverse antimicrobial activity including antibacterial and antifungal activity against the tested strains. The genome sequencing data revealed that this isolate was B. cereus based on the average nucleotide identity (ANI) (>99%) to reference strains. antiSMASH analysis of the genome revealed nine predicted secondary metabolite clusters including bacteriocins (2), non-ribosomal peptide synthetase (NRPS) (2), siderophore (1), sactipeptide (1), betalactone (1), linear azol(in)e-containing peptides (LAP) - bacteriocin (1) and a terpene (1). Some of these pathways had low to no sequence similarity to known pathways, indicating the potential of these pathways to produce novel compounds. One of the pathways showed very high sequence similarity to the thuricin CD pathway in Bacillus thuringiensis. Considering that thuricin CD has been reported to have antimicrobial activity against B. cereus (ATCC1072), it was hypothesised that it could also be produced by PE6-126. However, the antimicrobial extract from PE6-126 was tested for sensitivity to proteinase K and heat treatment, which thuricin CD is known to be sensitive to. The results revealed that the antimicrobial activity was not lost after treatment, implying that a different metabolite could be responsible for the anti-B. cereus activity. In addition, PE6-126 initially displayed antimicrobial activity against a multi-drug resistant E. coli 1699, suggesting some of the antimicrobial compound/(s) produced by this strain could potentially be novel. The bioassay-guided fractionation approach coupled to Liquid Chromatography Mass Spectrometry (LC-MS) did not lead to identification of the antimicrobial compound/(s), therefore it remains a question whether the secondary metabolite pathways predicted by antiSMASH lead to the production of the active compound/(s). The results from this study showed that even well studied species have the potential to synthesize as yet undescribed compounds, based on the novelty of some of the pathways. This study highlights the importance of employing a genome-guided approach in drug discovery, as there may be many novel compounds to discover from biosynthetic pathways that have not yet been characterised. Further research is needed to identify the antimicrobial compound/(s) produced by PE6-126.

The master´s thesis is focused on the study of biologically active compounds of fennel. The theoretical part describes basic characteristics of fennel and its chemical composition, further specifies plant´s biological active substances and antioxidants, also describes extraction techniques for obtaining these bioactive compounds, methods of their determination and verification of antimicrobial effect. In the experimental part were spectrophotometrically determined contents of polyphenols and flavonoids in the prepared extracts of fennel tea, whole and crush spice. On the basis of extraction curves, antioxidant activity and potential antimicrobial activity against the selected microorganisms Bacillus subtilis, Bacillus cereus, Serratia marcescens a Micrococcus luteus was determined in the samples with the highest values of the given bioactive substances. Among the all monitored extracts, the inhibitory effect was showed only by an aqueous extract of the fennel tea against the bacterial strain of Micrococcus luteus.

The presented doctoral thesis is focused on preparation of nanoparticles and nanofibers with natural active ingredient and testing their biological effects. Modern types of application forms were prepared from biomaterials based on one or more natural polymers. Chitosan particles were prepared from cross-linked polymer using ultrasonication. A mixture of soy lecithin and cholesterol was used for preparation of liposomes. Poly-3-hydroxybutyrate was used for preparation of combined liposomes, too. All liposome particles were prepared by ultrasonication. Nanofibers were obtained from polyhydroxybutyrate using electrospinning. Mixtures of low-molecular antioxidants obtained by extraction from natural sources were used as active ingredients. Different types of teas, barks, herbs, spices, fruits and vegetables were selected as sources of natural antioxidants. Total phenolic and flavonoid content and total antioxidant activity of extracts were determined using spectrophotometrical methods. Obtained natural extracts were subsequently used for encapsulation. Prepared application forms were characterized in terms of their physicochemical properties. Particle size was monitored by dynamic light scattering. Colloidal stability of particles in suspension was determined using zeta potential. Spectrophotometry was used to evaluate the efficiency of encapsulation of active compounds into particles. The morphology of the new type of combined PHB liposomes was monitored by electron microscopy. Chromatography was used for quantification of individual components of particles. Morphology of nanofibers and incorporation of active agent into their structure were monitored using FTIR-ATR spectroscopy and electron microscopy. Afterwards, antimicrobial, cytotoxic and genotoxic effects of preparations were evaluated. It was found that the most suitable types of extracts for liposome preparation are aqueous and lipid extracts of natural antioxidants. Prepared particles showed excellent stability and good encapsulation efficiency. The study confirmed that incorporation of polydroxybutyrate into liposome structure does not reduce neither the colloidal stability of the particle, nor the efficiency of encapsulation process. Antimicrobial and antimycotic effect of preparations against model microorganisms Micrococcus lutues, Serratia marcescens and Candida glabrata was detected. It was found that process of encapsulation increases the inhibitory effect of natural extracts of antioxidants. The safety of preparations was assessed using two human cell cultures: epidermal keratinocytes and HaCaT cell line. Assays of cell viability and plasma membrane integrity were used to determine cytotoxicity of preparations. Low toxicity of liposome particles was confirmed by a series of cytotoxic tests. Obtained data showed that association of phospholipid with PHB polymer does not cause a significant increase in cytotoxicity in human skin cells. Genotoxicity testing on model procaryotic organism confirmed zero genotoxic potential of preparations. The new type of combined particles and polymeric fibers cant thus be used as a carrier for active ingredients, complex natural extracts, antimicrobial agents and many others.

This doctoral thesis studies the properties and behaviour of phase-separated hydrogels. These can be prepared by interaction of polyelectrolytes with oppositely charged surfactants. Negatively charged polysaccharide hyaluronan and cationic surfactant carbethopendecinium bromide (Septonex), whose properties, behaviour and utilization are described in the first two chapters of theoretical part, were selected for this role. Hyaluronan is naturally-occuring in living organisms and is known for his specific targeting to the tumour cells. Septonex is used as antiseptic and disinfectant. Experimental part of this work is focused on examination of the structure and behaviour of these types of hydrogels especially from rheological point of view. The crucial part of this study was to establish mechanical properties and their dependence on environment. This led to design further studies. Structural analysis was held using the methods of ATR-FTIR, ionic chromatography and ICP-OES helping to measure the inner content of entry materials in the gels and supernatants respectively. The last chapter deals with antimicrobial activity. The results of this study indicate a potential usage of these substances in the field of medical applications.

Purpose of this thesis was research the content of biologically active substances in herbal rosehip extracts and also determination of antimicrobial and antioxidant activity of these extracts. Teoretical part describes informations about Rosa canina L., detailed specification of biologically active substances, specification of antioxidation and overview of methods determine antioxidant compound and antimicrobial activity. In the practical part was by combination of different solvents, procedures and herbal materials, made 21 extracts of Rosa canina L.. From measuring of these extracts, was made extraction curves and also was determined antimicrobial efficiency against bacterial strains Serratia marcescesns, Bacillus subtilis, Bacillus cereus and Micrococcus luteus. Results shows, that also all extracts has some antimicrobial activity, but only against microorganisms Micrococcus luteus and Bacillus cereus. Also was found that bud extracts contains more bioactive compounds soluble in ethanol, meanwhile rose hip extracts contains more bioactive compounds soluble in water.

>Magister Scientiae - MSc / Combating antimicrobial resistant infections caused by nosocomial pathogens poses a major public health problem globally. The widespread use of broad-spectrum antibiotics for the treatment of wound infections has led to the appearance of multidrug-resistant (MDR) microbes which further exacerbates the growth of microbes amongst patients. It may result in prolonged debility of the patient and an increase in healthcare costs due to prolonged hospital stays and expensive treatment regimens to avoid patient-patient transmission. Therefore, it is imperative that alternative sources of treatment to antimicrobial use in wound infections needs to be developed in order to inhibit or kill resistant microbes and to provide point of care medical treatment to the less fortunate at an affordable cost. / 2021-08-30

The oviduct plays an important role in the complex process of fertilization and in the early phase of embryo development. Isolation and characterization of some components of bovine oviduct participating in the formation of oviductal sperm reservoir was a subject of the present study. Two affinity sorbents containing immobilized components of bull seminal plasma (non-separated proteins of bull seminal plasma and their phosphorylcholine binding fraction) were prepared and used for the study of interaction of immobilized ligands with components of oviductal epithelium. Two types of preparation of oviductal membrane proteins of the isthmus region were isolated: complete membrane proteins and the apical fraction of membrane proteins. These preparations were separated using prepared affinity matrices. in both cases only an insignificant amount of proteins was found in the adsorbed fractions. Further attention has been paid to the identification of four protein zones detected after electrophoretic separation in the presence of SDS (rel. mol. wt. 15 500 - 18 500) in the fraction of apical membrane proteins. These proteins were identified after the electrophoretic separation and tryptic digestion using MS analysis as bovine histones H4, H2A typ 2-C, H2B typ 1-K a H3.3. Proteins identified as bovine...

Streptomycetes, primary soil saprophytic microorganisms are at the center of interest in many research groups, mainly because of their ability to produce a wide range of biologically active substances useful in medicine, biotechnology and agriculture. The marginal, and little explored areas are the interactions that streptomycetes create with humans. Recent metagenomic studies have shown that streptomycetes colonize the skin, the respiratory and possibly the urogenital tract of humans. In addition to apparent pathogens such as S. somaliensis and S. sudanensis, the clinical impact of these streptomycetes on human health is unknown. For this reason, a unique collection of non-pathogenic streptomycetes isolated from human clinical specimens was developed. The isolates were collected by the National Reference Laboratory for Pathogenic Actinomycetes in Trutnov, Czech Republic. On the basis of pilot studies, an isolate labeled TR42 was selected from the Trutnov collection, showing a very broad spectrum of biological activities. This strain was isolated from sputum from a patient with unknown respiratory diagnosis. The TR42 strain exhibits considerable biotechnological potential and after following a thorough study, it could be a source of new biologically active substances with pharmaceutically...

M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Sciences), Vaal University of Technology. / The aim of the study is to synthesise, characterize and assess the antimicrobial activity of cobalt oxide, zinc oxide and cobalt-doped zinc oxide nanoparticles against selected waterborne pathogenic fungi (yeasts and moulds) and bacteria. Various types of oxide based nanomaterial are an attractive option for the disinfection of water due to its high chemical stability and non-toxicity towards human cells. Synthesis of Co -doped ZnO and Co3O4nanoparticles was done through mechanochemical synthesis and urea based synthesis and microwave heating was employed for the preparation of ZnO nanoparticles. The ZnO nanoparticles were produced in short reaction and it was white color. Cobalt oxide (Co3O4) nanoparticles appeared as a pink precipitate but was turned black after being calcined. The synthesis of Co- ZnO nanoparticles was successfully prepared and blue solid was obtained from pink cobalt ion solution. The nanoparticles were characterised by X- Ray Diffraction (XRD), Fourier Infrared Spectroscopy (FTIR), UV–visible spectroscopy, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) (Yang et al. 2003). In this research project, the antibacterial activities of NPs were carried out by well diffusion method and minimum inhibitory concentration (MIC). MIC is the lowest concentration of a chemical, usually a drug, which prevents visible growth of bacterium. Bacterial strains used in the study are: Salmonella enterica, Escherichia coli, Shigella sonnei and Staphylococcus aureus, yeast and mould is: Candida albicans and Aspergillus niger. The antimicrobial results obtained showed that ZnO nanoparticles are more effective than Co- ZnO and Co3O4 nanoprticles against all the microorganisms used. The toxicity studies were performed using DAPHTOXKIT F and the 24h EC50 and 48h EC50 were calculated according to the manufactures’ instructions. The results showed that Co- ZnO nanoparticles is less toxic to Daphnia magna compared to ZnO and Co3O4 NPs.

Tesis por compendio / [EN] In the present Doctoral Thesis, different strategies to improve functional properties of starch films for food packaging applications were analysed: study of the effect of amylose:amylopectin ratio, blend with other polymers poly(vinyl alcohol) (PVA), and incorporation of different fillers (rice bran and cellulose nanocrystals-CNCs) and antimicrobial agents (neem oil-N, oregano essential oil-O and silver nanoparticles-AgNPs). Likewise, a biodegradation study of the films as affected by antimicrobials was carried out. Among different starches with distinct amylose:amylopectin ratio, pea starch was selected with higher values of this ratio. The high content of amylose gave rise to stiffer and more resistant to fracture films, with lower oxygen permeability, which decreased during storage. Pea starch-PVA (S-PVA) blend films represented a good strategy to improve film properties without a notable increase in cost. The PVA addition led to films which were less water soluble and not as sensitive to water sorption, more extensible and resistant than neat starch films, while they maintained the high oxygen barrier and provided stability to the matrix during ageing. In this sense, S-PVA ratios near to 1:1 are recommendable. When rice bran with the smallest particle size was used as filler, it improved the elastic modulus of the films, but reduced the film stretchability and barrier properties, due to the enhancement of the water binding capacity and the introduction of discontinuities in the matrix. Incorporation of CNCs into S-PVA films, as a reinforcing material, enhanced phase separation of polymers, did not imply changes in water vapour barrier of the films but improved the film mechanical performance: they became stiffer and more stretchable, while crystallization of PVA was partially inhibited. Silver loaded S-PVA films exhibited antimicrobial activity against the fungi (Aspergillus niger and Penicillium expansum) and bacteria (Listeria innocua and Escherichia coli) genera, depending on the silver concentration. Silver nanoparticles provoked notable changes in the film colour and transparency but no relevant changes in the other physical properties. Silver was completely delivered to aqueous simulants within the firsts 60 minutes of contact, but the film release capacity drastically decreased in the non-polar simulant, where the overall migration limit for food contact packaging materials (60 mg/Kg simulant) was accomplished. So, the use of the developed films as food packaging materials should be restricted to fat-rich foodstuffs. The incorporation of oregano essential oil (O), as antimicrobial agents, into the S-PVA matrix gave rise to active films against bacteria and fungi, whereas films containing neem oil (N) were not effective. Higher O concentration in the films was required to observe antifungal effect with respect to the antibacterial activity. Oils did not notably affect water sensitivity and water barrier properties of the films, but at high ratio, oils implied weaker film networks, affecting their mechanical performance. Blend of starch with PVA significantly improved PVA biodegradation and disintegration behaviour. Incorporation of silver species to S-PVA films slowed down their biodegradation kinetics while increased their degradation ratio. However, no significant effect of O was observed on the biodegradability indices despite the antimicrobial activity detected for this oil. N even promoted biodegradation of S-PVA films. Finally, a food application of biopolymer coatings was studied, using chitosan and essential oils (oregano or rosemary) to prevent weight loss and fungal development of semi-hard goat's milk cheeses. Coating were highly effective at reducing fungal growth and cheese weight loss while slightly reduced lipolytic and proteolytic activities in the cheese. Sensory evaluation revealed that the cheeses double coated with chitosan-oregano oil were the best evaluated in terms of aroma and flavour. / [ES] En la Tesis Doctoral, se han analizado diferentes estrategias para mejorar las propiedades funcionales de películas de almidón para aplicaciones de envasado de alimentos: el estudio del ratio amilosa:amilopectina, mezclas con otros polímeros (alcohol de polivinilo-PVA), y la incorporación de diferentes refuerzos (salvado de arroz y nanocristales de celulose-CNCs) y agentes antimicrobianos (aceite de neem-N, aceite esencial de orégano-O y nanopartículas de plata-AgNPs). También se realizó un estudio de biodegradación de las películas observando el efecto de los antimicrobianos. Entre los diferentes almidones con distinto ratio amilosa:amilopectina, se seleccionó el almidón de guisante con altos valores de amilosa. El alto contenido en amilosa dio lugar a películas más rígidas y resistentes a la fractura, con baja permeabilidad al oxígeno, la cual disminuyó durante el almacenamiento. Las películas de mezcla de almidón-PVA (S-PVA) representaron una buena estrategia para mejorar las propiedades de las películas sin incrementar notablemente el precio. La adición de PVA dio lugar a películas menos solubles en agua, menos sensibles a su absorción y más extensible y resistentes que las de almidón puro, mientras mantuvieron alta barrera al oxígeno y dieron estabilidad a la matriz durante el envejecimiento. Son recomendables los ratios de S-PVA cercanos a 1:1. El salvado de arroz con menor tamaño de partícula, mejoró el modulo elástico de las películas, pero su extensibilidad y propiedades barrera empeoraron debido a la mejor capacidad de retención de agua y a las discontinuidades introducidas. La incorporación de CNCs en las películas de S-PVA incrementó la separación de fases de los polímeros, sin cambios en la permeabilidad al vapor de agua, y mejoró las prestaciones mecánicas: películas más rígidas y extensibles, mientras que inhibió parcialmente la cristalización del PVA. Las películas de S-PVA con partículas de plata exhibieron actividad antimicrobiana contra dos hongos y dos bacterias, dependiendo de la concentración de plata. Las AgNPs provocaron cambios en el color de las películas así como en su transparencia. La plata fue completamente liberada en los primeros 60 minutos en contacto con simulantes acuosos, sin embargo la liberación disminuyó en simulantes no polares, donde se cumple el límite de migración global. Por lo tanto, el uso de las películas desarrolladas para envasado de alimentos debe ser restringido a productos alimenticios ricos en grasas. La incorporación de O en la matriz de S-PVA dio lugar a películas activas contra bacterias y hongos, mientras que las películas con N no fueron efectivas. Se necesitaron concentraciones más altas de O en las películas para observar un efecto antifúngico respecto a la actividad bactericida. Los aceites no afectaron notablemente la sensibilidad ni las propiedades barreras al agua de las películas, aunque la mayor proporción de aceite dio lugar a películas con una red más débil, afectando sus prestaciones mecánicas. La mezcla de S con PVA mejoró significativamente el comportamiento de biodegradación y desintegración de las películas. La incorporación de AgNPs a películas de S-PVA disminuyó su cinética de biodegradación mientras aumentó su ratio de degradación. La adición de O no presentó efecto significativo en el índice de biodegradación a pesar de la actividad antimicrobiana detectada. El N incluso mejoró la biodegradación de las películas. Finalmente, se realizó una aplicación de recubrimientos basados en biopolímeros, usando quitosano-CH y aceite esencial de orégano o romero para evitar la pérdida de peso y el desarrollo de hongos en quesos de cabra semicurados. Los recubrimientos fueron efectivos en la reducción del crecimiento fúngico y la pérdida de peso de los quesos, mientras que la actividad lipolítica y proteolítica ligeramente disminuyó. El análisis sensorial reveló q / [CA] S'han analitzat diferents estratègies per a millorar les propietats funcionals de pel·lícules de midó per a aplicacions d'envasat d'aliments: l'estudi de la ràtio amilosa:amilopectina, mescles amb altres polímers (alcohol polivinílic-PVA), i la incorporació de diferents reforços (segó d'arròs i nanocristalls de celulosa-CNCs) i agents antimicrobians (oli de neem-N, oli essencial d'orenga-O i nanopartícules de plata). També es va fer un estudi de biodegradació de les pel·lícules per observar l'efecte dels antimicrobians. Entre els diferents midons amb distint ràtio amilosa:amilopectina, es va seleccionar el midó de pèsol amb alts valors d'amilosa. L'alt contingut en amilosa va donar lloc a pel·lícules més rígides i resistents a la fractura, amb baixa permeabilitat a l'oxigen, la qual va disminuir durant l'emmagatzemament. Les pel·lícules de mescla de S-PVA van representar una bona estratègia per a millorar les propietats de les pel·lícules sense incrementar notablement el preu. L'addició de PVA va donar lloc a pel·lícules menys solubles en aigua, menys sensibles a la seua absorció i més extensible i resistents que les de midó pur. A més van mantenir l'alta barrera a l'oxigen i van donar estabilitat a la matriu durant l'envelliment. Son recomanables les ràtios de S- PVA pròxims a 1:1. El segó d'arròs amb menor tamany de partícula, va millorar el mòdul elàstic de les pel·lícules, però la seua extensibilitat i propietats barrera van empitjorar. La incorporació de CNCs en les pel·lícules de S-PVA, va incrementar la separació de fases dels polímers, sense implicar canvis en la permeabilitat al vapor d'aigua, però millorant les prestacions mecàniques: pel·lícules més rígides i extensibles, al mateix temps que es va inhibir parcialment la cristal·lització del PVA. Les pel·lícules de S-PVA amb partícules de plata van exhibir activitat antimicrobiana front a dos de fongs i dos bacteris, depenent de la concentració de plata. Les AgNPs van provocar canvis en el color de les pel·lícules així com en la seua transparència. La plata va ser completament alliberada en els primers 60 minuts en contacte amb simulants aquosos. La capacitat d'alliberament va disminuir en simulants no polars, on es complix el límit de migració global. Per tant, l'ús de les pel·lícules desenvolupades per a l'envasat d'aliments ha de ser restringit a productes alimentaris rics en greixos. La incorporació d'O en la matriu de S-PVA va donar lloc a pel·lícules actives front a bacteris i fongs. Pel contrari les pel·lícules amb N no van ser efectives. Van ser necessàries concentracions més elevades d'O en les pel·lícules per a observar un efecte antifúngic respecte a l'activitat bactericida. Els olis no van afectar la sensibilitat a l'aigua ni les propietats barrera a l'aigua de les pel·lícules, però la major proporció d'oli va donar lloc a pel·lícules amb una xarxa més dèbil, afectant les seues prestacions mecàniques. La mescla de S amb PVA va millorar significativament el comportament de biodegradació i desintegració. La incorporació de partícules de plata a pel·lícules de S-PVA va disminuir la seua cinètica de biodegradació mentre que va augmentar la seua ràtio de degradació. No obstant això, l'addició d'O no va presentar un efecte significatiu en els índexs de biodegradació a pesar de l'activitat antimicrobiana detectada. L'N fins i tot va millorar la biodegradació de les pel·lícules de S-PVA. Finalment, es va realitzar una aplicació de recobriments basats en biopolímers, fent ús de quistosà-CH i olis essencials de orenga i romer per evitar la pèrdua de pes i el desenvolupament de fongs en formatges de cabra semi-curats. Els recobriments van ser altament efectius en la reducció del creixement fúngic i la pèrdua de pes dels formatges. L'activitat lipolítica i proteolítica en els formatges va disminuir suaument. L'anàlisi sensorial va revelar que els form / Cano Embuena, AI. (2015). Different strategies to improve the functionality of biodegradable films based on starch and other polymers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/55383 / Premios Extraordinarios de tesis doctorales / Compendio