Key role of alternative oxidase in lovastatin solid-state fermentation

Area of Science:

• Biotechnology
• Microbial Physiology
• Metabolic Engineering

Background:

• Lovastatin, a key statin precursor, is produced by Aspergillus terreus.
• Reactive oxygen species (ROS) positively regulate lovastatin biosynthesis genes.
• Aeration levels significantly impact lovastatin yield in solid-state fermentation (SSF).

Purpose of the Study:

• Investigate the mechanism behind reduced lovastatin production under high aeration in SSF.
• Determine the role of ROS and alternative respiration in lovastatin production during SSF.

Main Methods:

• Comparative analysis of ROS accumulation under varying aeration conditions in SSF.
• Measurement of alternative oxidase (AOX) activity and aox gene expression.
• Assessment of exogenous ROS (H2O2) impact on AOX activity in SSF and submerged fermentation (SmF).

Main Results:

• High aeration in SSF led to lower ROS accumulation, correlating with reduced lovastatin production.
• Alternative oxidase (AOX) was expressed during the idiophase in SSF, with higher aeration inducing greater AOX activity.
• Induced AOX activity under high aeration acts as a mechanism to limit ROS generation, maintaining optimal signaling for lovastatin production.
• AOX activity was not detected in SmF, even with exogenous ROS addition.

Conclusions:

• Alternative respiration via AOX is a critical factor in regulating ROS levels during SSF of lovastatin.
• The induction of AOX by high oxygen availability in SSF indirectly supports lovastatin production by managing ROS.
• This mechanism highlights a key difference between SSF and SmF in lovastatin production regarding ROS and alternative respiration.