Transcriptional regulation of genes encoding extracellular enzymes produced by strains of Aspergillus niger and Trichoderma reesei using solid state fermentation

Sheena Fagan, Richard Murphy

Author address: 

Alltech, Dunboyne, Co. Meath, Ireland


Over the past decades, many cellulolytic fungi have been isolated and their relevant enzymes characterised. However, compared with the number of isolates, very little research was dedicated to understanding the induction and repression mechanisms of cellulolytic enzymes produced using solid state fermentation (SSF) techniques. The biotechnological importance of filamentous fungi and associated enzymes has accelerated an interest in understanding the regulation of gene expression and the characterisation of the transcription factors involved. The ability to regulate gene expression and to adapt to environmental changes helps living organisms to survive. Study of regulation phenomena by genetic and molecular methods are therefore of growing interest, not only because of biotechnological importance, but also from an evolutionary point of view. Most of the published results are related to growth of filamentous fungi under submerged fermentation conditions and very little is known about gene expression under solid state conditions. In this study, the transcript expression levels of a number of candidate regulatory elements including ace1, ace2, creA, cre1, hapB, pacC, xlnR, xyrI, and areA were examined after cultivation of Aspergillus niger and Trichoderma reesei in solid state fermentations supplemented with different carbon and nitrogen sources. It was anticipated that this type of analysis would enable a direct evaluation of effect of nutrient supplementation on gene expression and facilitate identification of possible co-regulation mechanisms, which would assist in the optimisation of culture conditions for enzyme production. In the present study, the analysis of gene expression revealed noticeable differences not only between solid state and submerged fermentations, but also between the two strains. It was concluded that certain carbon sources induced high levels of expression of one gene or a set of genes, such as those induced in T. reesei cultures, whereas the effect on expression of other genes was weak or insignificant, as was evident with A. niger supplemented cultures.

abstract No: 


Full conference title: 

    • ECFG 9th (2008)