Environmental cues that induce the physiology of solid medium: a study on lovastatin production by Aspergillus terreus.

ABSTRACT

AIMS: The aim of this work was to identify the main environmental factors that induce the special physiology displayed by fungi growing in solid culture-that is, higher secondary metabolite (SM) production-compared with those in submerged culture. METHODS AND RESULTS: Lovastatin-specific production (SP) was used as an indicator of the physiological status, and different model culture systems were used to evaluate the impact of potential solid-state fermentation (SSF) environmental stimuli. Direct contact with air was identified as an important stimulus. Cultures with two or more hours of exposure to air showed typical SSF lovastatin SP (1462% higher than cultures exposed for 0·08 h). Intermediate times of exposure generated intermediate physiological states. Support-related stimuli also induced higher lovastatin SP, even in a liquid environment (679% increase). CONCLUSIONS: Direct contact with air, as well as support-related stimuli, are major environmental cues that induce the physiology of solid medium. SIGNIFICANCE AND IMPACT OF THE STUDY This knowledge is the starting point to investigate how these environmental cues are sensed and transduced, impacting SM and enzyme production. These results have important applied potential in new strategies to generate overproducing strains, as well as application in the design of novel production systems.