Analysis of the Aspergillus oryzae transcriptome in relation to enzymatic degradation of sugarcane bagasse

Fungi are an important source of hydrolytic enzymes for industrial scale-based conversion of lignocellulose residues to fermentable sugars for application in second generation biofuel production. The principal objective of our study was to examine the transcriptome in Aspergillus oryzae BLU37, a promising fungal strain for hydrolytic enzyme production on lignocellulose sources. A. oryzae spore suspensions at a final concentration of 1 x 10⁸ spores/mL were used to inoculate semi-solid and liquid media cultures containing a minimal medium plus specific carbon source [glucose 0.5% (w/v); pre-treated sugarcane bagasse (pH 7.0) 1% (w/v)]. Cultures were incubated at 28°C over a time-course of 36 h and 48 h, totaling eight distinct treatments carried out in duplicate. Following total RNA isolation from harvested fungal mycelia, messenger RNA isolation, full-length enriched cDNA library preparation and Illumina RNAseq (www.Illumina.com) was carried out by Eurofins MWG Operon (Alabama, USA). Quality-trimmed reads were mapped to the A. oryzae RIB40 genome (National Research Institute of Brewing Stock Culture ATCC-42149). The CarbohydrateActive Enzyme database (CAZy - http://www.cazy.org/) identified 202 genes belonging to CAZy families expressed by A. oryzae under liquid growth condition treatment with statistically significant differences in expression (padj < 0.01). A total of 44 genes belonging to five transcription factors families were also identified according to the Fungal Transcription Factor Database (FTFD - http://ftfd.snu.ac.kr). Ongoing analysis of differentially expressed genes through QRT-PCR will contribute to our understanding of the complexity of the A. oryzae transcriptome, for long term employment of this fungus in second generation biofuel development.