Dorota Kręgiel

Nanostructured multilayer polyelectrolyte films with silver nanoparticles as antibacterial coatings

Ultrathin polyelectrolyte films containing silver nanoparticles appear to be a promising material for antimicrobial coatings used in the medical area. The present work is focused on the formation of multilayer polyelectrolyte films using: polyethyleneimine (PEI) as polycation, Poly(sodium 4-styrenesulfonate) (PSS) as polyanions and negatively charged silver nanoparticles (AgNPs), which led to the polyelectrolyte-silver nanocomposite coatings. The film thickness and mass were measured by ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) and the structure and morphology of films were visualized using scanning electron microscopy (SEM). Systematic increase of the UV-Vis absorption confirmed formation of the consecutive layers of the film. The analysis of bacteria cell adhesion to films surface was done by the luminometry measurement. Three gram-negative bacterial strains with strong adhesive properties were used in this study: Escherichia coli, Aeromonas hydrophila, and Asaia lannenesis. It was found that nanocomposite films have antimicrobial properties, which makes them very interesting for a number of practical applications, e.g. for the prevention of microbial colonization on treated surfaces.

Growth and metabolic activity of conventional and non-conventional yeasts immobilized in foamed alginate.

The aim of this research was to study how the cell immobilization technique of forming foamed alginate gels influences the growth, vitality and metabolic activity of different yeasts. Two distinct strains were used, namely conventional yeast (exemplified by Saccharomyces cerevisiae) and a non-conventional strain (exemplified by Debaryomyces occidentalis). The encapsulation of the yeast cells was performed by the traditional process of droplet formation, but from a foamed alginate solution. The activities of two key enzymes, succinate dehydrogenase and pyruvate decarboxylase, together with the ATP content were measured in both the free and immobilized cells. This novel method of yeast cell entrapment had some notable effects. The number of living immobilized cells reached the level of 10(6)-10(7) per single bead, and was stable during the fermentation process. Reductions in both enzyme activity and ATP content were observed in all immobilized yeasts. However, S. cerevisiae showed higher levels of ATP and enzymatic activity than D. occidentalis. Fermentation trials with immobilized repitching cells showed that the tested yeasts adapted to the specific conditions. Nevertheless, the mechanical endurance of the carriers and the internal structure of the gel need to be improved to enable broad applications of alginate gels in industrial fermentation processes, especially with conventional yeasts. This is one of the few papers and patents that describe the technique of cell immobilization in foamed alginate and shows the fermentative capacities and activities of key enzymes in immobilized yeast cells.

Health Safety of Soft Drinks: Contents, Containers, and Microorganisms

Soft drinks consumption is still a controversial issue for public health and public policy. Over the years, numerous studies have been conducted into the possible links between soft drink intake and medical problems, the results of which, however, remain highly contested. Nevertheless, as a result, increasing emphasis is being placed on the health properties of soft drinks, by both the industry and the consumers, for example, in the expanding area of functional drinks. Extensive legislation has been put in place to ensure that soft drinks manufacturers conform to established national and international standards. Consumers trust that the soft drinks they buy are safe and their quality is guaranteed. They also expect to be provided with information that can help them to make informed decisions about the purchase of products and that the information on product labels is not false or misleading. This paper provides a broad overview of available scientific knowledge and cites numerous studies on various aspects of soft drinks and their implications for health safety. Particular attention is given to ingredients, including artificial flavorings, colorings, and preservatives and to the lesser known risks of microbiological and chemical contamination during processing and storage.

Simultaneous Saccharification and Fermentation of Sugar Beet Pulp for Efficient Bioethanol Production

Sugar beet pulp, a byproduct of sugar beet processing, can be used as a feedstock in second-generation ethanol production. The objective of this study was to investigate the effects of pretreatment, of the dosage of cellulase and hemicellulase enzyme preparations used, and of aeration on the release of fermentable sugars and ethanol yield during simultaneous saccharification and fermentation (SSF) of sugar beet pulp-based worts. Pressure-thermal pretreatment was applied to sugar beet pulp suspended in 2% w/w sulphuric acid solution at a ratio providing 12% dry matter. Enzymatic hydrolysis was conducted using Viscozyme and Ultraflo Max (Novozymes) enzyme preparations (0.015–0.02 mL/g dry matter). Two yeast strains were used for fermentation: Ethanol Red (S. cerevisiae) (1 g/L) and Pichia stipitis (0.5 g/L), applied sequentially. The results show that efficient simultaneous saccharification and fermentation of sugar beet pulp was achieved. A 6 h interval for enzymatic activation between the application of enzyme preparations and inoculation with Ethanol Red further improved the fermentation performance, with the highest ethanol concentration reaching 26.9 ± 1.2 g/L and 86.5 ± 2.1% fermentation efficiency relative to the theoretical yield.

Enhancing adhesion of yeast brewery strains to chamotte carriers through aminosilane surface modification

The adhesion of cells to solid supports is described as surface-dependent, being largely determined by the properties of the surface. In this study, ceramic surfaces modified using different organosilanes were tested for proadhesive properties using industrial brewery yeast strains in different physiological states. Eight brewing strains were tested: bottom-fermenting Saccharomyces pastorianus and top-fermenting Saccharomyces cerevisiae. To determine adhesion efficiency light microscopy, scanning electron microscopy and the fluorymetric method were used. Modification of chamotte carriers by 3-(3-anino-2-hydroxy-1-propoxy) propyldimethoxysilane and 3-(N, N-dimethyl-N-2-hydroxyethyl) ammonium propyldimethoxysilane groups increased their biomass load significantly.

Phenolic Compounds Contained in Little-known Wild Fruits as Antiadhesive Agents Against the Beverage-Spoiling Bacteria Asaia spp.

The aim of the study was to evaluate antioxidant activity and total phenolic content of juice from three different types of fruits: elderberry (Sambucus nigra), lingonberry (Vaccinium vitis-idaea) and cornelian cherry (Cornus mas), and their action against adhesion of bacterial strains of Asaia lannensis and Asaia bogorensis isolated from spoiled soft drinks. The antioxidant profiles were determined by total antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl, DPPH), and ferric-reducing antioxidant power (FRAP). Additionally, total polyphenol content (TPC) was investigated. Chemical compositions of juices were tested using the chromatographic techniques: high-performance liquid chromatography (HPLC) and liquid chromatography–mass spectrometry (LC-MS). Adhesion properties of Asaia spp. cells to various abiotic materials were evaluated by luminometry, plate count and fluorescence microscopy. Antioxidant activity of fruit juices expressed as inhibitory concentration (IC50) ranged from 0.042 ± 0.001 (cornelian cherry) to 0.021 ± 0.001 g/mL (elderberry). TPC ranged from 8.02 ± 0.027 (elderberry) to 2.33 ± 0.013 mg/mL (cornelian cherry). Cyanidin-3-sambubioside-5-glucoside, cyanidin-3-glucoside, and cyanidin-3-sambubioside were detected as the major anthocyanins and caffeic, cinnamic, gallic, protocatechuic, and p-coumaric acids as the major phenolic acids. A significant linear correlation was noted between TPC and antioxidant capacity. In the presence of fruit juices a significant decrease of bacterial adhesion from 74% (elderberry) to 67% (lingonberry) was observed. The high phenolic content indicated that these compounds may contribute to the reduction of Asaia spp. adhesion.

Cell lysis induced by membrane-damaging detergent saponins from Quillaja saponaria

This paper presents the results of a study to determine the effect of Quillaja saponaria saponins on the lysis of industrial yeast strains. Cell lysis induced by saponin from Q. saponaria combined with the plasmolysing effect of 5% NaCl for Saccharomyces cerevisiae, Kluyveromyces marxianus yeasts biomass was conducted at 50 °C for 24-48 h. Membrane permeability and integrity of the yeast cells were monitored using fluorescent techniques and concentrations of proteins, free amino nitrogen (FAN) and free amino acids in resulting lysates were analyzed. Protein release was significantly higher in the case of yeast cell lysis promoted with 0.008% Q. saponaria and 5% NaCl in comparison to plasmolysis triggered by NaCl only.

Growth and by-product profiles of Kluyveromyces marxianus cells immobilized in foamed alginate.

The aim of this research was to study how the yeast cell immobilization technique influences the growth and fermentation profiles of Kluyveromyces marxianus cultivated on apple/chokeberry and apple/cranberry pomaces. Encapsulation of the cells was performed by droplet formation from a foamed alginate solution. The growth and metabolic profiles were evaluated for both free and immobilized cells. Culture media with fruit waste produced good growth of free as well as immobilized yeast cells. The fermentation profiles of K. marxianus were different with each waste material. The most varied aroma profiles were noted for immobilized yeast cultivated on apple/chokeberry pomace. Copyright

Effect of Plasma Processing and Organosilane Modifications of Polyethylene on Aeromonas hydrophila Biofilm Formation

The aim of our research was to study how the modifications of polyethylene—a material commonly used in medicine and water industry—influence bacterial cell attachment and biofilm formation. The native surface was activated and modified using two-step process consisting in the activation of native surface with a H2O vapor plasma followed by its treatment with various organosilanes, namely, [3(tertbutylamine-2hydroxy) propyloxypropyl] diethoxymethylsilane, 1H,1H,2H,2H-perfluorooctylmethyldimethoxysilane, dimethoxydimethylsilane, and isobutylmethyldimethoxysilane. The effect of polyethylene modification after chemical treatment was analyzed using surface tension measurement. The adhesive properties of Aeromonas hydrophila LOCK0968 were studied in water with a low concentration of organic compounds, using luminometric and microscopic methods, and the viability of the adhered bacterial cells was evaluated using the colony forming units method. After two-week incubation the chemically modified materials exhibited better antiadhesive and antibacterial characteristics in comparison to the native surface. Among the examined modifying agents, dimethoxydimethylsilane showed the best desired properties.

Black Currant (Ribes nigrum L.) and Bilberry (Vaccinium myrtillus L.) Fruit Juices Inhibit Adhesion of Asaia spp.

The aim of the study was to evaluate the activity of high-polyphenolic black currant (Ribes nigrum L.) and bilberry (Vaccinium myrtillus L.) juices against bacterial strains Asaia lannensis and Asaia bogorensis isolated as spoilage of commercial soft drinks. The composition of fruit juices was evaluated using chromatographic techniques HPLC and LC-MS. The adhesion to glass, polystyrene, and polyethylene terephthalate in two different culture media was evaluated by luminometry and the plate count method. The major anthocyanins in the V. myrtillus were petunidin-3-glucoside, malvidin-3-glucoside, cyanidin-3-glucoside, and delphinidin-3-glucoside, while in R. nigrum delphinidin-3-rutinoside and cyanidin-3-rutinoside were detected. The LC-MS analysis showed presence of anthocyanins (delphinidin, cyanidin, petunidin, and malvidin derivatives), phenolic acids (chlorogenic and neochlorogenic acids), flavonols (quercetin-3-glucoside, quercetin-3-rutinoside), and flavanols (procyanidin B2 and procyanidin type A2). Additionally, in the bilberry juice A type procyanidin trimer was detected. The adhesion of Asaia spp. cells depended on the type of medium, carbon sources, and the type of abiotic surfaces. We noted that the adhesion was significantly stronger in minimal medium containing sucrose. The addition of bilberry and black currant juices notably reduced bacterial growth as well as cell adhesion to polyethylene terephthalate surfaces.