Abstract
The basidiomycete Gloeophyllum trabeum KU-41 can degrade Japanese cedar wood efficiently. To construct a strain better suited for biofuel production from Japanese cedar wood, we developed a gene transformation system for G. trabeum KU-41 using the hygromycin phosphotransferase-encoding gene (hpt) as a marker. The endogenous laccase candidate gene (Gtlcc3) was fused with the promoter of the G. trabeum glyceraldehyde-3-phosphate dehydrogenase-encoding gene and co-transformed with the hpt-bearing pAH marker plasmid. We obtained 44 co-transformants, and identified co-transformant L#61, which showed the highest laccase activity among all the transformants. Moreover, strain L#61 was able to degrade lignin in Japanese cedar wood-containing medium, in contrast to wild-type G. trabeum KU-41 and to a typical white-rot fungus Phanerochaete chrysosporium. By using strain L#61, direct ethanol production from Japanese cedar wood was improved compared to wild type. To our knowledge, this study is the first report of the molecular breeding of lignin-degrading brown-rot fungus and direct ethanol production from softwoods by co-transformation with laccase overproduction constructs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-015-0173-9) contains supplementary material, which is available to authorized users.
Highlights
Gloeophyllum trabeum, along with Postia placenta, is a well-characterized brown-rot fungus used as a model laboratory organism
Genetic transformation of KU-41 protoplasts with 10 μg of the marker plasmid pAH yielded 26–35 transformants; no clones were obtained in the absence of pAH (Table 1)
In the present study, we investigated the appropriate conditions for preparing protoplasts of the KU-41 strain, because preparation of a sufficient number of protoplasts is essential for construction of a genetic transformation system
Summary
Gloeophyllum trabeum, along with Postia placenta, is a well-characterized brown-rot fungus used as a model laboratory organism. Brown-rot fungi are important recyclers in coniferous forest ecosystems and cause a highly destructive type of wood decay. Elucidating the mechanisms employed by brown-rot fungi in the biodegradation of lignified plant cell walls is very important. A Fenton system is proposed to play an important role in cellulose decomposition by brown-rot fungi (Arantes et al 2012). This system recently has been receiving increased attention because utilization of this process could facilitate the cost-effective transformation of lignocellulose biomass into biofuel or renewable chemicals (Kerem et al 1999; Jensen et al 2001).
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