Structure optimisation of biopigment prodigiosin from Serratia marcescens ATCC 27117 and antimicrobial and anticancer properties of novel halogenated derivativesJelena Lazić
, 2022, doctoral dissertation
Abstract: Prodigiosins (PGs) are a class of bacterial secondary metabolites with remarkable biological activities and colour. In this study, optimised fermentative production of prodigiosin (PG) using waste processed meat as a substrate has been achieved to levels of 83.1 ± 3.0 mg/L from a commercially available Serratia marcescens ATCC 27117 strain within 12 h. Methods were established for the reliable PG extraction from both the bacterial cell pellet and the culture supernatant, while gravitation column chromatography was used to obtain pure bacterial PG.
The structure of the isolated PG was optimised by environmentally acceptable oxidative bromination reactions, obtaining mono- and dibrominated derivatives (PG-Br and PG-Br2). Chemical structures were confirmed by structural characterisation using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), showing that PG-Br is a mixture of two monobrominated isomers in approximately equal ratios, while PG-Br2 was afforded as a pure derivative.
PG and its brominated derivatives (Br-derivatives) showed anticancer potential with half-maximal inhibitory concentration (IC50) values ranging from 0.62 to 17.00 μg/mL on four tested cancer cell lines (A549 lung, A375 skin, MDA-MB-231 breast, HCT116 colon) and an induction of early apoptosis, but low selectivity against healthy cell lines (MRC-5 lung fibroblasts and HaCaT skin keratinocytes). All three PG, PG-Br and PG-Br2 compounds did not affect roundworms (Caenorhabditis elegans) at concentrations up to 50 μg/mL. However, an improved toxicity profile of Br-derivatives in comparison to the parent PG was observed in vivo using zebrafish (Danio rerio) model system, when 10 μg/mL applied at 6 h post fertilisation caused death rate of 100, 30 and 0% by PG, PG-Br and PG-Br2, respectively, which is a significant finding for further structural optimisations of bacterial PGs.
Keywords: prodigiosin, Serratia marcescens, meat waste, halogenation, novel derivatives, anticancer activity, apoptosis, zebrafish embryotoxicity
Published in RUNG: 21.10.2022; Views: 881; Downloads: 27
Full text (3,39 MB)
Plastic Waste Precursor-Derived Fluorescent Carbon and Construction of Ternary FCs@CuO@TiO2 Hybrid Photocatalyst for Hydrogen Production and Sensing ApplicationAkansha Metha
, Rayees Ahmad Rather
, Blaž Belec
, Sandra Gardonio
, Ming Fang
, Matjaž Valant
, 2022, original scientific article
Abstract: A sustainable nexus between renewable energy production and plastic abatement is imperative for overall sustainable development. In this regard, this study aims to develop a cheaper and environmentally friendly nexus between plastic waste management, wastewater treatment, and renewable hydrogen production. Fluorescent carbon (FCs) were synthesized from commonly used LDPE (low-density polyethylene) by a facile hydrothermal approach. Optical absorption study revealed an absorption edge around 300 nm and two emission bands at 430 and 470 nm. The morphological analysis showed two different patterns of FCs, a thin sheet with 2D morphology and elongated particles. The sheet-shaped particles are 0.5 μm in size, while as for elongated structures, the size varies from 0.5 to 1 μm. The as-synthesized FCs were used for the detection of metal ions (reference as Cu2+ ions) in water. The fluorescence intensity of FCs versus Cu2+ ions depicts its upright analytical ability with a limit of detection (LOD) reaching 86.5 nM, which is considerably lesser than earlier reported fluorescence probes derived from waste. After the sensing of Cu2+, the as-obtained FCs@Cu2+ was mixed with TiO2 to form a ternary FCs@CuO@TiO2 composite. This ternary composite was utilized for photocatalytic hydrogen production from water under 1.5 AM solar light irradiation. The H2 evolution rate was found to be ~1800 μmolg−1, which is many folds compared to the bare FCs. Moreover, the optimized FCs@CuO@TiO2 ternary composite showed a photocurrent density of ~2.40 mA/cm2 at 1 V vs. Ag/AgCl, in 1 M Na2SO4 solution under the illumination of simulated solar light. The achieved photocurrent density corresponds to the solar-to-hydrogen (STH) efficiency of ~0.95%. The efficiency is due to the fluorescence nature of FCs and the synergistic effect of CuO embedded in TiO2, which enhances the optical absorption of the composite by reaching the bandgap of 2.44 eV, apparently reducing the recombination rate, which was confirmed by optoelectronic, structural, and spectroscopic characterizations.
Keywords: plastic waste, fluorescent carbo, sensing of metal ions, photocatalytic hydrogen production
Published in RUNG: 25.02.2022; Views: 1094; Downloads: 37
Full text (5,98 MB)
Anaerobic treatment of excess yeast and waste ethanol from alcohol free beer production for increase of renewable energy use in brewing industryGregor Drago Zupančič
, Mario Panjicko
, Goran Lukić
, 2020, published scientific conference contribution
Abstract: In the presented paper we have investigated how large quantities of excess yeast and periodical releases of waste ethanol influence the operation of the anaerobic treatment process in a UASB reactor. The process was tested in a pilot-scale reactor with a design organic load of 16.0 kg/m3/day of COD. Through various stages of the experiment, several possible scenarios were tested, excess yeast was added continuously with concentrations up to 3 vol. %, whereas waste ethanol was added in batches of up to 0.8 % of daily volume load several days a week. The intent was to test real conditions in the treatment process. The whole experiment lasted for 77 days, where the maximum organic load of 24.72 kg/m3/day was successfully achieved with no adverse effects on the efficiency of the reactor performance although it significantly surpassed the design load. The COD efficiency at maximum OLR was 83.1 %, whereas the average was 88.0 %. The average biogas production rate increased from 2,044 m3/m3/day to 4.927 m3/m3/day. The microbial community structure analysis showed significant shifts only in the archaeal community (25 – 30 %) as a good adaptation to the addition of substrates. Monitoring the model brewery in applying the addition of yeast and ethanol to the wastewater treatment showed a 110 % increase in biomethane production. The consequence of the increased biomethane production is that the natural gas substitute ratio could be increased from the current average of 10.7 % to potentially 20.1 %, which is a substantial step towards the goal of renewable energy use.
Keywords: anaerobic digestion, biogas, brewery yeast, renewable energy, waste ethanol
Published in RUNG: 10.06.2021; Views: 1973; Downloads: 10
Link to full text
This document has many files! More...
Factors influencing collected quantities of municipal solid wasteSlavica Schuster
, 2019, doctoral dissertation
Abstract: The first part of the survey, using the survey (enclosed with the annexes), tried in various ways to identify samples and facts by which we could predict the amount of waste collected according to some social and economic indicators of all municipalities of the Republic of Slovenia. Data were collected through surveys to determine the way we work and think about the collection of waste and landfills. For my research I have selected the Republic of Slovenia and its 212 municipalities. It is precisely Slovenia that in many respects represents a bright spot in waste management and management.
In the second part of the research we used statistical methods to find the factors that influence the increase of waste. From the results we have proved our hypotheses and one of the most important is how the average age of people influences the increase of waste. We did the research over a period of 6 years (2012-2017). Where, by comparison, we find that they do not change significantly in structure by age, but of course socio-economic indicators such as average age change.
In the last section, we compared the growth of waste collected with GDP growth. We show that with the growth of GDP, the amount of waste collected also increases. The research is also based on the Republic of Slovenia and beyond. In the second part of the last survey we also included data for EU Member States (28 of them).
Keywords: waste, waste management, amount of waste, socio-economic impacts, Slovenia, wild-landfills, GDP
Published in RUNG: 02.10.2019; Views: 3495; Downloads: 223
Full text (3,88 MB)