Details zur Publikation

Kategorie Textpublikation
Referenztyp Qualifizierungsarbeiten
Titel (primär) Laccases from green algae: occurrence, characteristics, and possible functions and uses
Autor Otto, B.
Erscheinungsjahr 2016
Department UMB
Seite bis 79
Sprache englisch
Abstract Laccases are multicopper oxidases, which are hitherto known in higher plants, fungi, insects, and
prokaryotes. These enzymes are typically extracellular glycoproteins and catalyze the oxidation of
a multitude of mainly phenolic substrates to their corresponding radicals. They are involved in
various biological processes, such as lignification, delignification, and detoxification. Laccases
are very interesting biocatalysts for numerous biotechnological applications as well, for instance
in bioremediation, bleaching processes and the synthesis of pharmaceuticals. While the biodegradation
of recalcitrant aromatic compounds has extensively been studied in bacteria and fungi,
green algae are just now increasingly recognized to biotransform compounds like synthetic dyes
and phenolic micropollutants. In the present thesis, green algae were for the first time demonstrated
to produce laccases, and basic structural and catalytic properties, the abundance and
possible biological functions and uses of green algal laccases were investigated.
At first, the production and partial characterization of an extracellular laccase-like enzyme in
culture supernatants of the terrestrial green microalga Tetracystis aeria is reported in chapter 2.
As depicted in chapter 3, the algal enzyme was then purified 120–fold by means of protein
chromatography. According to its substrate specificity, the purified enzyme was designated to be
a laccase. It apparently is a hetero-oligomeric protein complex with the composition AB2, wherein
subunit A is catalytically active. A high molecular mass and high glycan content of the catalytic
subunit, neutral pH optima toward phenolic substrates and a rather weak activity toward syringaldazine
resemble features of laccases from higher plants. As reported in chapters 3 and 4, the
Tetracystis laccase enables the biotransformation of recalcitrant compounds, which include
synthetic dyes and phenolic micropollutants such as bisphenol A, 17α-ethinylestradiol, nonylphenol
and triclosan, in the presence of redox mediators. Furthermore, lignin and humic acid can
be modified to some extent by the algal laccase-mediator system, though an effective degradation
of lignin appears unlikely. A screening for laccase-like activities and further studies with selected
species indicated that ‘true’ laccases are widespread in the Moewusinia group of chlorophycean
green algae. In contrast, algae of the ‘Scenedesmus’-clade were found to produce yet unknown,
exceedingly thermostable redox-active compounds, as described in chapter 4.
Possible biological functions of green algal laccases may relate to the biosynthesis of cell wallassociated
polymers and other protective compounds, or to the detoxification of harmful phenolic
compounds. The enzymes might influence processes like humification when released into the
environment. Laccase-producing green algae may contribute to the natural attenuation of phenolic
trace pollutants and are of interest for applications like the biotreatment of contaminated effluents.
dauerhafte UFZ-Verlinkung
Otto, B. (2016):
Laccases from green algae: occurrence, characteristics, and possible functions and uses
Dissertation, Universität Leipzig, Fakultät für Biowissenschaften, Pharmazie und Psychologie
79 pp.