Fig. 2

Schematic representation of strategies for strain improvement by exploiting of light dependent effects. Gene regulation in T. reesei is considerably influenced by light, with the light signal coordinated with nutrient signals via the signal transduction pathways of heterotrimeric G-proteins and cAMP signaling. Posttranscriptional regulation of cellulase gene expression is triggered by a G-protein coupled receptor, whose signal is channeled through the G-protein pathway and its subunits. The consequences of light exposure include changes in normal enzyme production, production of heterologous proteins and secondary metabolites expressed from homologous or heterologous gene clusters. Once the mechanisms of light dependent regulation are understood, this information can serve to improve performance under currently applied industrial conditions (dark fermentors) by knowledge based genetic engineering. Additionally, screening procedures are recommended to be performed under controlled light conditions and inoculum production can be improved. For high value products, illumination or specifically applied light regimes in photobioreactors can be evaluated