Enhancing the Laccase Production and Laccase Gene Expression in the White-Rot Fungus Trametes velutina 5930 with Great Potential for Biotechnological Applications by Different Metal Ions and Aromatic Compounds

Yang Yang,Fangfang Fan,Li Ma,Rui Zhuo,Xiaoyu Zhang,Fuxiang Wei,Chen Zhang,Mulan Jiang,Huahua Liu,Melanie R Mormile

doi:10.1371/journal.pone.0079307

Abstract

Laccase is useful for various biotechnological and industrial applications. The white-rot fungus Trametes velutina 5930 and its laccase, isolated from the Shennongjia Nature Reserve in China by our laboratory, has great potential for practical application in environmental biotechnology. However, the original level of laccase produced by Trametes velutina 5930 was relatively low in the absence of any inducer. Therefore, in order to enhance the laccase production by Trametes velutina 5930 and make better use of this fungus in the field of environmental biotechnology, the regulation of laccase production and laccase gene expression in Trametes velutina 5930 were investigated in this study. Different metal ions such as Cu2+ and Fe2+ could stimulate the laccase synthesis and laccase gene transcription in Trametes velutina 5930. Some aromatic compounds structurally related to lignin, such as tannic acid, syringic acid, cinnamic acid, gallic acid and guaiacol, could also enhance the level of laccase activity and laccase gene transcription. We also found that there existed a positive synergistic effect of aromatic compound and metal ion on the laccase production and laccase gene transcription in Trametes velutina 5930. Taken together, our study may contribute to the improvement of laccase productivity by Trametes velutina 5930.

Highlights

White-rot fungi are unique in their strong ability to extensively degrade lignin and mineralize a variety of recalcitrant synthetic chemicals similar to lignin in structure
We found that different metal ions as well as the aromatic compounds with different structure could stimulate the laccase gene transcription and laccase synthesis in Trametes velutina 5930
We have previously cloned and characterized a laccase gene, lac5930-1, and its corresponding full-length complementary DNA (cDNA) from white-rot fungus Trametes velutina 5930 isolated from Shennongjia Nature Reserve in China [21]

Summary

Introduction

White-rot fungi are unique in their strong ability to extensively degrade lignin and mineralize a variety of recalcitrant synthetic chemicals similar to lignin in structure. Due to its capability of biodegrading xenobiotics and recalcitrant pollutants, white-rot fungi have been widely applied in bioremediation and environmental biotechnology [1,2]. White-rot fungi, which are mostly basidiomycetes, can secrete extracellular and non-specific lignin modifying enzymes (LMEs) that play an important role in the degradation of lignin and xenobiotics. The ligninolytic enzymes of white-rot fungi mainly comprise of lignin peroxidase (LiP), manganese dependent peroxidase (MnP), and laccase [1,3]. As a ligninolytic enzyme produced by white-rot fungi, laccase exhibits a broad substrate specificity and unique ability of biodegradation [4]. Laccase has been widely applied in many fields, such as delignification of lignocellulosic biomass, detoxification of recalcitrant pollutants, decolorization of industrial dyes and textile dye effluents, biological bleaching in pulp and paper industries, juice and wine clarification, and biosensors [5,6]

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Results

Discussion

Conclusion