Iskanje po katalogu digitalne knjižnice

Opis: The environment hosts a diversity of microorganisms whose potential for biotechnological applications has not yet been exhausted. The quest of our study was to find isolates of Pichia kudriavzevii from the environment that could be used as new biotechnological agents. Moreover, we aimed to explore the resource efficiency for microbial cultivation, in particular the efficiency of spent coffee grounds (SCG), an easily accessible waste coffee product with a high unutilized organic content. In this study, Pichia kudriavzevii strain ZMUM_K002, a yeast strain isolated from a grape pomace compost, was investigated. Antifungal susceptibility, particularly fluconazole susceptibility, was assessed, and the strain’s biotechnological potential by comparing its ability to utilize low-cost carbon sources, including SCG, with a natural isolate of Saccharomyces cerevisiae (strain ZMUM_K003) was assessed. The P. kudriavzevii strain ZMUM_K002 exhibited higher fluconazole susceptibility and yielded more than 30% more biomass in optimized media formulations compared to S. cerevisiae ZMUM_K003. These findings demonstrate that P. kudriavzevii ZMUM_K002 has the potential for efficient biomass production in sustainable industrial biotechnology, particularly in processes requiring high biomass yields on alternative substrates.
Ključne besede: Pichia kudriavzevii, Candida krusei, environmental sampling, biomass production, sauerkraut, safety assessment, spent coffee grounds
Objavljeno v DKUM: 21.03.2025; Ogledov: 0; Prenosov: 6
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Opis: Lignocellulosic biomass has been widely recognized as a renewable feedstock that has enormous potential for the production of bio-based fuels and platform chemicals. Obtained from the dehydration of sugars, 5-hydroxymethylfurfural (HMF) in particular has received extensive consideration due to its diverse functionality and versatility. However, despite its potential, major technical and economic challenges still need to be addressed before HMF valorization technologies can be competitive with current processes that rely on fossil fuels. This doctoral study specifically focuses on the catalytic hydrogenation of HMF into various platform chemicals while utilizing nickel-based catalysts. The overall goal of this dissertation is to advance these technologies through innovative catalyst design and catalyst characterization techniques that allowed for a systematic investigation into the major catalyst surface properties that influence activity and product selectivity. Various characterization techniques were applied to acquire relevant catalyst surface and structural properties including temperature-programmed reduction, temperature-programmed desorption, X-ray powder diffraction, and transition electron microscopy, N2 physisorption, and diffuse reflectance infrared Fourier transform spectroscopy. A detailed kinetic model was also established that takes into account the number of metallic active sites that provides comparative kinetic parameters to better understand catalyst activity. The main discoveries obtained during this doctoral thesis include the determination of the critical influence that the support material has on catalyst activity and tuning the reaction network. Particularly, it was found that carbon as a relatively neutral support was effective for hydrodeoxygenation, however, an alumina support was necessary to activate the furan ring and facilitate ring saturation and ring opening reactions. The solvent system was also found to be impactful where incorporating water as a co-solvent completely eliminated all dehydration side reactions. Structural-activity correlations indicate that both acid and basic active sites could play a pivotal role in dictating between the two competing reactions of ring saturation and ring opening. The results presented in this doctoral dissertation provide crucial details for more optimal catalyst design and operating conditions for the effective conversion of 5-hydroxymethylfurfural via hydrogenation for the purpose of advancing sustainable bio-based chemical production.
Ključne besede: biomass, catalysis, kinetics, hydrogenation, 5-hydroxymethylfurfural
Objavljeno v DKUM: 19.09.2024; Ogledov: 0; Prenosov: 18
Celotno besedilo (12,16 MB)

Opis: In this work, the thermochemical properties of municipal solid waste (MSW) are studied using the torrefaction process as the main method for investigation. Torrefaction experiments were carried out using an electric laboratory furnace, at temperatures of 200, 250, and 300 °C. The residence time was set to 90 min. Proximate and ultimate analysis were performed on the torrefied MSW samples and compared with the properties of the raw MSW samples. In addition, the thermal properties of the obtained torrefied MSW samples were evaluated by thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The following could be stated: the obtained results showed that mass and energy yields (MY and EY, respectively) decrease with increasing when torrefaction temperature, while the heating values (HHV) increased under the same conditions (from 24.3 to 25.1 MJ/kg). Elemental analysis showed an increase in carbon content (C), from 45.7 ± 0.9 to 52.8 ± 1.05 wt.%, and decrease in oxygen content (O), from 45.6 ± 0.9 to 39.5 ± 0.8 wt.%, when torrefaction temperature is increased, which is consistent with the general definition of the torrefaction process. In addition, enhancement factors (EFs) and fuel ratios (FRs) were calculated, which ranged from 1.00 to 1.02 and 0.16 to 0.23, respectively. Some anomalies were observed during the thermal analysis, which are assumed to be related to the composition of the selected MSW. This study therefore shows that torrefaction pretreatment can improve the physicochemical properties of raw MSW to a level comparable to coal, and could contribute to a better understanding of the conversion of MSW into a valuable, solid biofuel.
Ključne besede: biomass, municipal solid waste, torrefication, energy yield, thermogravimetric analysis
Objavljeno v DKUM: 10.05.2024; Ogledov: 255; Prenosov: 24
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Opis: The main objective of this review is to present the latest research results regarding the importance of the torrefaction process for different biomass materials in the last 12-year period. Despite the fact that the potential of renewable energy sources has been analyzed, research regarding that of energy derived from waste biomass still remains in the infancy state. Torrefaction is known to be one of the most effective methods for enhancing the energy efficiency of biomass. Among different types of torrefactions, the focus in this study is mostly on dry torrefaction. The influential factors, like temperature and residence time, and physico-chemical properties of torrefied products, and the prospective of torrefaction due to its reduced impact on environment, are discussed in-depth. This review provides valuable insights into the torrefaction process, which is conducive to upgrading biomass for achieving net zero carbon emissions, as it has been stated in several works that torrefied biomass can be used instead of coal.
Ključne besede: torrefaction, lignocellulosic biomass, waste biomass, biomass properties
Objavljeno v DKUM: 22.03.2024; Ogledov: 470; Prenosov: 704
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Opis: In Slovenia, approximately one third of electricity is produced in thermal power plants. Electricity prices have risen sharply recently. There are several reasons for this. One of them is the large increase in the price of CO2 coupons that thermal power plants have to buy, since they emit large amounts of greenhouse gas into the environment during the production of electricity. Emissions of the greenhouse gas CO2 are the result of burning fossil fuels, in this case coal. We want to use renewable energy sources to replace fossil fuels and reduce greenhouse gas emissions. More than half of Slovenia is covered with forest, and as a result, wood biomass energy represents a great energy potential. One possibility is the use of wood biomass in a classic thermal power plant for the production of electricity. This contribution presents the energy potential of Slovenian forests, before evaluating the replacement of the energy source in the existing coal-based thermal power plant with wood biomass. It has been discovered that there is enough wood biomass in Slovenia, and that all the electricity that is currently produced from coal can be produced from wood biomass. The cost of wood biomass is higher than the cost of coal. By changing the energy source, we save on the purchase of CO2 coupons. Therefore, the use of wood biomass represents an economically justified energy source for the production of electricity.
Ključne besede: wood biomass, thermal power plant, electricity production
Objavljeno v DKUM: 30.10.2023; Ogledov: 443; Prenosov: 10
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