We demonstrated different kinetics of free oxygen radical production during laccase-catalyzed oxidation of lignoceluloze fibers (sisal, coconut) containing different chemical composition of lignin. EPR technique was used to directly detect kinetics of long - living fee radical formation; in addition the spin trapping method was used for detection of short-living radical kinetics. DMP was used for trapping and identification of radical spices and their quantities formed during laccase activity and other secondary radical reactions.
B.06 Other
COBISS.SI-ID: 14101526This paper, followed invited lecture of prof. J. Štrancar, presents a strategy for inspecting of laccase oxidation of phenol-type substrates, caffeic and gallic acids as monomers and commercial lignins as complex polymers, and their polymerization traced via HPLC-SEC. The transfer of electrons and stable radical intermediates were detected with CV and EPR spectroscopy. The oxidation of mediators was determined via stable water-soluble nitroxide radicals, and the generation of short-lived radicals as well as their reduction kinetics was measured using DMPO as spin-trap converting short-lived radicals into long-lived radical DPMO-adducts.
B.05 Guest lecturer at an institute/university
COBISS.SI-ID: 15421462Molecular studies suggest that diversity and composition of bacterial laccases are highly dependent on the environment, but intra-species diversity was rather limited (e.g. Bacillus subtilis strains). 1,200 putative laccases were identified in 2200 draft and completed genomes (custom models pHMM), uncovering their mobility within bacteria and the broad range of laccases' putative physiological functions. The characterization these laccases indicated great variability in their pH and temperature optima suggesting that bacteria represent an underexplored pool of these interesting biocatalysts.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 4129656The PhD dissertation is in large part devoted to the laccase activity in the presence of phenolic and phenolic-like substances. Several chemical and physical methods for the characterisation of the catalytic activity of laccases, and for the description of the kinetics and final products of the action of these enzymes on various lignocellulosic surfaces were used. The knowledge of the analytical methods and the acquired information on laccase function were an essential base for the utilisation of these enzymes for the functionalisation of lignocellulosic surfaces.
F.03 Increased qualifications of the research and development staff
COBISS.SI-ID: 771959The Ph.D. thesis is the first one in Slovenia and also among the first world-wide that addresses diversity and function of bacterial laccases. Laccases are oxidoreductases that couple the oxidation of phenolic and other substrates with reduction of oxygen to water. They have been used in a variety of biotechnological applications and have been mostly studied in fungi in spite of having been found in all domains of life. The present work addresses bacterial laccases, their occurrence and diversity within bacteria and aims to uncover these genes in the natural environment. The drained peat soils of the Ljubljana marsh were chosen for this purpose, since they harbor a diverse bacterial community and are naturally enriched in phenolic compounds. Multiple novel groups of genes were identified in this soil using a cloning and sequencing approach. Moreover, bioinformatics analyses of available bacterial sequenced genomes showed that genes for laccase-like enzymes were present in all bacterial phyla. Evidence evidence of the mobility of these genes within bacterial domain is also presented. In the final part of the thesis, heterologous expression, purification and partial biochemical characterization of one selected laccase gene from Thioalkalivibrio sp. is described. The novel enzyme is an alkaliphilic laccase that could oxidize phenolic compounds in alkaline pH and could thus potentially be useful in future biotechnological applications.
F.03 Increased qualifications of the research and development staff
COBISS.SI-ID: 4370040