Abstract
The laccase producing fungus HC1 was isolated from a sample collected in the Bolivian Amazon region. Analysis of 5.8S and 28S rDNA, and internal transcribed spacer 1 and 2 sequences revealed that isolate HC1 belongs to genus Galerina. High production of laccase was achieved in basal salt medium supplemented with 30 g L-1 glucose, 10 g L-1 yeast extract and 0.01 g L-1 copper sulphate. The enzyme production was further improved by addition of 2,5-xylidine, α-benzoin oxime and p-coumaric acid, but strongly repressed by sinapyl alcohol, 3-(dimethylamino)benzoic acid, hydroquinone, 1-naphthale-neacetic acid, 2,6-dichlorophenol and 3-methyl-2-benzothiazolinone hydrazone. Cultivation under optimum conditions in the presence of 2 mmol L-1 2,5-xylidine and 0.01 g L-1 copper sulphate, resulted in the enzyme yield of over 26 000 U L-1. Galerina sp. HC1 could also produce laccase in media composed of orange peels both in submerged- and solid-state fermentations. The laccase (0.5 U ml-1) from Galerina sp. was able to decolorize over 60% of 35 μmol L-1 Congo red in 2 h in the presence of 2,2-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt as mediator, and 65% of 30 µmol L-1 Coomassie Brilliant Blue G-250 in 5 min using syringaldehyde as mediator. The laccase was immobilized on cross-linked chitosan and used efficiently to decolorize the dyes. Key words: Oxidase, inducer, immobilized enzyme, enzyme production, solid-state cultivation.
Highlights
Laccases (EC 1.10.3.2) are multicopper oxidases that are among the most abundant members of the oxidoreductase family, which catalyze oxidation of various substrates using molecular oxygen as the electron acceptor
To 30 ml basal medium supplemented with 4 g L-1 glucose, 4 g L1 yeast extract and 0.05 g L-1 CuSO4·5H2O were added different chemical additives (1 mol l-1) or 1 g L-1 lignin (Eucalyptus Kraft lignin kindly provided by Innventia AB, Stockholm) and laccase production was followed over a period of 20 days
HC1 was grown in liquid basal medium containing (g L-l): glucose, 4; yeast extract, 4 and
Summary
Laccases (EC 1.10.3.2) are multicopper oxidases that are among the most abundant members of the oxidoreductase family, which catalyze oxidation of various substrates using molecular oxygen as the electron acceptor. To 30 ml basal medium supplemented with 4 g L-1 glucose, 4 g L1 yeast extract and 0.05 g L-1 CuSO4·5H2O were added different chemical additives (1 mol l-1) or 1 g L-1 lignin (Eucalyptus Kraft lignin kindly provided by Innventia AB, Stockholm) and laccase production was followed over a period of 20 days. Based on a preliminary study, three different concentrations of glucose, yeast extract and copper sulphate were chosen to study the effect on laccase production by Galerina sp.
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