Analysis of ethanol fermentation mechanism of ethanol producing white-rot fungus Phlebia sp. MG-60 by RNA-seq.

BACKGROUND: The white-rot fungus Phlebia sp. MG-60 shows valuable properties such as high ethanol yield from several lignocellulosic materials, although white-rot fungi commonly degrade woody components to CO2 and H2O. In order to identify genes involved in ethanol production by Phlebia sp. MG-60, we compared genes differentially expressed by the ethanol producing fungus Phlebia sp. MG-60 and the model white-rot fungus Phanerochaete chrysosporium under ethanol fermenting and non-fermenting conditions using next-generation sequencing technologies. RESULTS: mRNAs from mycelia of Phlebia sp. MG-60 and P. chrysosporium under fermenting and non-fermenting conditions were sequenced using the MiSeq system. To detect differentially expressed genes, expression levels were measured in fragments per kilobase of exon per million mapped reads (FPKM). Differentially expressed genes were annotated using BLAST searches, Gene Ontology classifications, and KEGG pathway analysis. Functional analyses of differentially expressed genes revealed that genes involved in glucose uptake, glycolysis, and ethanol synthesis were widely upregulated in Phlebia sp. MG-60 under fermenting conditions. CONCLUSIONS: In this study, we provided novel transcriptomic information on Phlebia sp. MG-60, and these RNA-seq data were useful in targeting genes involved in ethanol production for future genetic engineering.

Aerobic H2 production related to formate metabolism in white-rot fungi.

Biohydrogen is mainly produced by anaerobic bacteria, anaerobic fungi, and algae under anaerobic conditions. In higher eukaryotes, it is thought that molecular hydrogen (H2) functions as a signaling molecule for physiological processes such as stress responses. Here, it is demonstrated that white-rot fungi produce H2 during wood decay. The white-rot fungus Trametes versicolor produces H2 from wood under aerobic conditions, and H2 production is completely suppressed under hypoxic conditions. Additionally, oxalate and formate supplementation of the wood culture increased the level of H2 evolution. RNA-seq analyses revealed that T. versicolor oxalate production from the TCA/glyoxylate cycle was down-regulated, and conversely, genes encoding oxalate and formate metabolism enzymes were up-regulated. Although the involvement in H2 production of a gene annotated as an iron hydrogenase was uncertain, the results of organic acid supplementation, gene expression, and self-recombination experiments strongly suggest that formate metabolism plays a role in the mechanism of H2 production by this fungus. It is expected that this novel finding of aerobic H2 production from wood biomass by a white-rot fungus will open new fields in biohydrogen research.