Transcriptome-wide analysis of a superior xylan degrading isolate Penicillium oxalicum 5–18 revealed active lignocellulosic degrading genes

Lignocellulose biomass raw materials have a high value in energy conversion. Recently, there has been growing interest in using microorganisms to secret a series of enzymes for converting low-cost biomass into high-value products such as biofuels. We previously isolated a strain of Penicillium oxalicun 5–18 with promising lignocellulose-degrading capability. However, the mechanisms of lignocellulosic degradation of this fungus on various substrates are still unclear. In this study, we performed transcriptome-wide profiling and comparative analysis of strain 5–18 cultivated in liquid media with glucose (Glu), xylan (Xyl) or wheat bran (WB) as sole carbon source. In comparison to Glu culture, the number of differentially expressed genes (DEGs) induced by WB and Xyl was 4134 and 1484, respectively, with 1176 and 868 genes upregulated. Identified DEGs were enriched in many of the same pathways in both comparison groups (WB vs. Glu and Xly vs. Glu). Specially, 118 and 82 CAZyme coding genes were highly upregulated in WB and Xyl cultures, respectively. Some specific pathways including (Hemi)cellulose metabolic processes were enriched in both comparison groups. The high upregulation of these genes also confirmed the ability of strain 5–18 to degrade lignocellulose. Co-expression and co-upregulated of genes encoding CE and AA CAZy families, as well as other (hemi)cellulase revealed a complex degradation strategy in this strain. Our findings provide new insights into critical genes, key pathways and enzyme arsenal involved in the biomass degradation of P. oxalicum 5–18.