Aspergillus terreus AtfB (bZIP) differently regulates lovastatin production in submerged fermentation and in solid-state fermentation.

Abstract

Lovastatin is industrially produced with Aspergillus terreus, generally by liquid submerged fermentation (SmF), but also by solid-state fermentation (SSF) since it shows higher yields. Its biosynthetic genes are positively regulated by reactive oxygen species. AtfB (AtatfB) knocked-down mutants displayed increased sensitivity to oxidative and osmotic stress in conidia. Transformants showed decreased lovastatin production in SSF, while increased production in SmF (also lower ROS levels in both systems). After ROS normalization, the differences in lovastatin production originally found were conserved. Moreover, biosynthetic genes expression (lovE and lovF) was higher in SmF, but lower in SSF. It is concluded that AtAtfB regulates lovastatin biosynthesis in A. terreus at transcriptional level, but has different functions in SmF and SSF, acting as a negative regulator in SmF, and as a positive regulator in SSF. This is the first report of a transcription factor regulating secondary metabolism with opposite functions in SSF and in SmF.