Abstract
Among seven carbon sources tested, glycerol and glucose favored the Cerrena unicolor laccase production (18.8-20.3 U/mL); in addition, glycerol ensured the highest manganese peroxidase (MnP) activity (2 U/mL). Substitution of glycerol with the ethanol production residue (EPR) gave the highest laccase (90.1 U/mL) activity, while the walnut pericarp provided the highest MnP activity (7.4 U/mL). Supplementation of medium with 1 mM copper and 1 mM xylidine at appropriate time caused significant additive effect on laccase expression (333.2 U/mL) in shake-flask experiments. Overproduction of laccase activity (507 U/mL) and secretion of MnP activity was obtained when C. unicolor was cultivated in stirred-tank fermenter. C. unicolor showed several distinctive and attractive technological features: it is capable to synthesize high levels of oxidases under high carbon and high nitrogen conditions and it secretes high laccase activity during trophophase.
Highlights
White-rot basidiomycetes (WRB) are known to be efficient lignocellulose degraders and they are recognized for their unique capability to degrade lignin secreting lignin peroxidase (EC 1.11.1.14), manganese-dependent peroxidase (EC 1.11.1.13), and laccase (EC 1.10.3.2), which function together with hydrogen peroxide-producing oxidases (Aro et al 2005)
Maximum laccase activity was revealed in the glucose containing medium while the highest manganese peroxidase (MnP) activity (2 U/ mL) was achieved in medium with glycerol
ethanol production residue (EPR), wheat bran, and mandarin peels provided the best laccase production yielding as high as 87.5-90.1 U/mL
Summary
White-rot basidiomycetes (WRB) are known to be efficient lignocellulose degraders and they are recognized for their unique capability to degrade lignin secreting lignin peroxidase (EC 1.11.1.14), manganese-dependent peroxidase (EC 1.11.1.13), and laccase (EC 1.10.3.2), which function together with hydrogen peroxide-producing oxidases (Aro et al 2005). Besides their fundamental importance for efficient bioconversion of plant residues in nature, lignin-modifying enzymes (LME) may have a large variety of biotechnological and environmental applications requiring huge amounts of these biocatalysts at a low cost (Madhavi and Lele 2009). Taking into account the potential applications of laccase in various biotechnologies, the enzyme production was scaled up in the laboratory fermenter employing the developed medium composition and creating cultivation conditions favorable for the target enzyme secretion
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