Ústav chemie potravin a biotechnologií

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Evaluating stress resilience of cyanobacteria through flow cytometry and fluorescent viability assessment
(Sringer, 2024-11-06) Kroupová, Zuzana; Slaninová, Eva; Mrázová, Kateřina; Krzyžánek, Vladislav; Hrubanová, Kamila; Fritz, Ines; Obruča, Stanislav
Cyanobacteria are prokaryotic organisms characterised by their complex structures and a wide range of pigments. With their ability to fix CO2, cyanobacteria are interesting for white biotechnology as cell factories to produce various high-value metabolites such as polyhydroxyalkanoates, pigments, or proteins. White biotechnology is the industrial production and processing of chemicals, materials, and energy using microorganisms. It is known that exposing cyanobacteria to low levels of stressors can induce the production of secondary metabolites. Understanding of this phenomenon, known as hormesis, can involve the strategic application of controlled stressors to enhance the production of specific metabolites. Consequently, precise measurement of cyanobacterial viability becomes crucial for process control. However, there is no established reliable and quick viability assay protocol for cyanobacteria since the task is challenging due to strong interferences of autofluorescence signals of intercellular pigments and fluorescent viability probes when flow cytometry is used. We performed the screening of selected fluorescent viability probes used frequently in bacteria viability assays. The results of our investigation demonstrated the efficacy and reliability of three widely utilised types of viability probes for the assessment of the viability of Synechocystis strains. The developed technique can be possibly utilised for the evaluation of the importance of polyhydroxyalkanoates for cyanobacterial cultures with respect to selected stressor-repeated freezing and thawing. The results indicated that the presence of polyhydroxyalkanoate granules in cyanobacterial cells could hypothetically contribute to the survival of repeated freezing and thawing.
Utilization of wheat bran protein isolate as a fortifier for production of high protein yoghurts
(CROATIAN DAIRY UNION, 2024-10-02) Slavíková, Zuzana; Smatana, Igor; Diviš, Pavel; Smilek, Jiří; Slaninová, Eva; Pořízka, Jaromír
Yoghurts with increased protein content are becoming very popular and beneficial across all age groups. The economic growth of the high-protein yoghurt market contributes to the production and research of various alternatives for these products. In this study, plain yoghurt was fortified with 2 % and 5 % wheat bran protein isolate (WBPI) before fermentation. The influence of the addition of WBPI on nutritional and rheological characteristics, bacteria growth, and sensory properties of yoghurt samples was evaluated. Apart from the nutritional benefits of wheat bran proteins, which have a favourable amino acid profile, fortification also resulted in changes in the rheological properties of the yoghurts. The increase in dry matter led to an increase in water holding capacity and, consequently, the viscosity of the yoghurt samples. The presence of WBPI did not affect bacterial growth or the fermentation process. However, the natural bitter taste of WBPI persisted even after the fermentation process, negatively influencing the sensory acceptability of WBPI-fortified yoghurt samples.
Application of biochar prepared from wheat bran as the binding phase in diffusive gradient in thin films technique for determination of mercury in natural waters
(SPRINGER INT PUBL AG, 2024-09-11) Křikala, Jakub; Diviš, Pavel; Pořízka, Jaromír; Duborská, Eva; Gajdušek, Martin
A novel binding gel for the DGT technique, containing biochar produced through the pyrolysis of wheat bran, was developed. The results of this study indicate that wheat bran biochar (WBBC) is a porous material with a surface area of 25 m2/g. The primary functional group on the surface of WBBC was identified as a carbonyl group, although some hydroxyl and imino groups were also detected. Furthermore, the findings demonstrate that the accumulation of Hg on WBBC was significantly influenced by an increase in ionic strength, particularly in NaCl solution, owing to Hg's high affinity for chloride ions. The performance of the DGT with WBBC binding gel was also affected by solution pH, with the optimal pH for WBBC application falling within the range of 3-7. The diffusion coefficient of Hg, depending on the matrix environment, varied between 5.44 and 6.99 x 10-6 cm2/s. When applying the newly designed DGT technique to spiked samples of river water, an R value of 0.68 was achieved. The results of this work proved that modified DGT technique allows for a cost-effective analysis of Hg in natural waters with lower salinity, while retaining the fundamental properties of the binding gel incorporating a particulate adsorbent with anchored functional groups.
The Effect of Biochar Particle Size on the Leaching of Organic Molecules and Macro- and Microelements
(MDPI, 2024-10-11) Bačovská, Šárka; Mravcová, Ludmila; Pořízka, Jaromír; Kubíková, Leona; Kalina, Michal
Biochar is a carbon-rich material that has recently received attention due to its increasing agronomical potential. The agricultural utilization of biochar relates to its potential to act in the soil as a soil conditioner; nevertheless, complex information on the direct dependence of biochar’s physical properties (texture, particle size) and corresponding leaching and availability of organic molecules (e.g., the polycyclic and heterocyclic organic compounds) and inorganic mineral salts (based on micro- and macroelements) is still inconsistent. Multi-elemental analysis by using inductively coupled plasma atomic emission spectroscopy (ICP-OES) was used to assess the information on the contents and availability of macro- and microelements in studied commercial biochar samples. The results showed a statistically significant indirect relation between an increase in the size fraction of biochar and the content of aqueous-extractable K and Na and the direct relation with the aqueous-extractable Ca, Mg, and P. Compared to the macroelements, the detected contents of aqueous-extractable microelements were almost three orders lower, and the dependence on fraction size was not consistent or statistically significant. In addition, gas chromatography (GC) coupled with mass spectroscopy (MS) was further used to reveal the concentrations of available polycyclic aromatic and heterocyclic compounds in biochar samples. The detected concentrations of these types of organic compounds were far below the certified limits, and a statistically significant indirect correlation with particle size was also observed for all the studied biochar samples. The proposed methodological concept could provide the necessary insights into the description of biochar mineral content and its connection to biochar texture, the physicochemical properties, and the potential of biochar to release nutrients into the soil. These findings could help in the further assessment of biochar as a soil conditioner in modern agriculture.
EXPLORING THE IMPACT OF DIFFERENT PACKAGING TYPES AND REPEATED PACKAGE OPENING ON VOLATILE COMPOUND CHANGES IN GROUND ROASTED COFFEE
(SLOVAK UNIV AGRICULTURE NITRA, 2024-08-02) Trenzová, Kristina; Gross, Michal; Vítová, Eva; Pořízka, Jaromír; Diviš, Pavel
In this study, the dynamics of volatile compound alterations during the storage of ground roasted coffee in various packaging were investigated using solid -phase microextraction-gas chromatography -mass spectrometry. Each type of packaging underwent repeated opening and closing, simulating the gradual consumption behavior of the consumer who consumes ground coffee in smaller doses over time. The experimental results revealed that after 30 days of storage, 35 to 45% of the volatile substances originally present in the coffee were lost regardless of the type of packaging used. Notably, storing coffee in a paper sachet proved to be the least effective method, resulting in a loss of over 80% of all volatile coffee substances during this storage period.

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