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Browsing by Subject "bioreporter"

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  • Degradation of bisphenol A (BPA) by fungal laccase-mediator systems 
    Le, Thanh Ngoc Uyen (2017)
    The aims of this study were to use the heterologously expressed laccase in Pichia pastoris as oxidative biocatalysts for the degradation of BPA and to find out natural mediators that could assist this laccase to degrade BPA efficiently and environmental friendly. In addition, removal of the estrogenic activity of BPA by the white rot fungus Physisporinus rivulosus cultures and the role of its laccase 2 in the BPA disapperance was also focused. Firstly, the removal of BPA’s estrogenic activity by the white rot fungus Physisporinus rivulosus was confirmed in cultures both with and without the fungal mycelium. Next, the recombinant laccase 2 (rLac2) played a role in the BPA disapperance. At the similar laccase activity level, removal of BPA’s estrogenic activity was done more efficiently in the fungal cultures than in the cell-free enzymatic treatments. Metabolites present in the fungal cultures could possibly act as natural mediators that enhance the removal of BPA. In addition, combination of nine laccases present in the fungal cultures could possibibly enhance the degradation of BPA. Finally, none of the ten mediatiors used was found to act as an efficient rLac2 enhancer in degrading BPA. Degradation of BPA was followed using a bioreporter system. The yeast Saccharomyces cerevisiae has been genetically modified in order to express the estrogen receptor alpha and produce a bioluminescent signal upon contact with estrogenic substances such as BPA. This bioreporter system has been further developed to specifically detect the estrogenic activity of bisphenol A and to be used in a high-throughput manner.
  • Optimization of bioluminescent bioreporters for macrolides 
    Troupp, Minna (2022)
    The increasing use of antimicrobials causes a heavy pollution load on the environment and can enhance antimicrobial resistance of pathogenic bacteria, thus having a negative impact on human and animal health. Antibiotic concentrations in the environment are constantly monitored, however traditional chemical analyses fail to provide data on the bioavailability of antimicrobials. Whole-cell bacterial bioreporters have been developed to detect a wide variety of environmental pollutants including antimicrobials. These living, genetically engineered organisms can also be used for the measurement of the bioavailable fraction in a sample and thus bioreporters could give insights on the role of antimicrobial pollution in the dissemination of antimicrobial resistance. The aim of this study was to design and construct an improved bioluminescent bioreporter for detection of macrolide antibiotics. The mrx gene and the mph(A)R repressor gene were coupled with the mph(A) promotor of the macrolide resistance operon mph(A) and the reporter genes of the luciferase operon luxCDABE. The main objective was to determine whether Mrx, the hydrophobic and putative transmembrane transport protein of the macrolide resistance operon mph(A), would improve the sensitivity and reduce the induction time. Another aim was to optimize the use of three existing bioreporters with other macrolides than erythromycin, which was used earlier in testing their performance. The mrx-mph(A)R fragment was cloned into the pmph(A)luxCDABE vector, and the bioreporter plasmid was introduced to Escherichia coli strain DH10B. After verification of the construct pmph(A)luxCDABE-mrx-mph(A)R, the usability of the new whole-cell biosensor was compared against the three existing macrolide bioreporters with three different macrolide and lincosamide antibiotics, erythromycin, tylosin and clindamycin. The cloning of the new bioluminescent bioreporter for macrolides was performed successfully. However, the addition of erythromycin, tylosin or clindamycin to a suspension of E. coli DH10B(pmph(A)luxCDABE-mrx-mph(A)R) did not stimulate the expression of the lux genes. High concentrations of all three antibiotics triggered a light response with the existing bioreporters although the response was slow. The results indicated that further studies on the mrx gene and its encoded Mrx protein are still needed. The response of the mph(A) operon to other macrolide and lincosamide antibiotics than erythromycin was a positive and encouraging finding, since this enables detection of other synthetic macrolides than erythromycin as well as lincosamides with the existing bioreporters after optimization.

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