The production of hemicellulases by microbial cells is governed by genetic and biochemical controls including induction, catabolite repression, or end product inhibition. In bioprocesses such as solid-state fermentation (SSF), the physiological status of the culture is traditionally measured indirectly by the analysis of extracellular variables such as biomass growth, exhaust gas concentrations and product formation. However, developments in molecular methods allow direct evaluation of cellular physiology by analysis of intracellular variables such as proteins, RNAs or metabolites. In addition, the availability of the genome sequence of Aspergillus niger has enabled the use of genomic techniques in gaining further insight into the regulation of growth, as well as carbon metabolism.
It is a well-established fact that culture conditions affect significantly the production of cellulases and hemicellulases, potentially converting a less productive fermentation into a high throughput process. In this work, the physiological results observed for A.niger 112 were studied at the molecular level by investigating regulation of cellulase and xylanase gene transcripts under conditions believed to induce or repress cellulase/xylanase activity. It was anticipated that gaining knowledge of genetic expressions in process conditions would enable further enhancement of this industrially relevant strain.