Precision fermentation of terpenes: tackling bottlenecks at enzyme, pathway, and bioprocess levels

Terpenoids are the most diverse class of natural products and serve as a rich source of functional ingredients for food, cosmetics, nutrition and therapeutics. Due to their complex structures and low abundance in nature, innovative fermentation and bioprocesses have been developed to enable biomanufacturing and deliver these valuable bioactive compounds to consumers. Nevertheless, despite progress, most successes for terpenoid production remain at the laboratory scale. To realize commercial-scale success, critical metabolic bottlenecks must be addressed. Notably, many enzymes within native biosynthetic pathways have not evolved to sustain high metabolic flux, leading to limited yields. Moreover, when enzymes are expressed in heterologous hosts, both cellular physiology and industrial-scale bioreactor conditions can further influence and impact enzyme performance. Comprehensive and iterative optimization at enzyme, pathway and process levels is required to achieve industry-ready bioprocesses. In this review, taking terpene synthase, one of the critical bottleneck enzymes, as an example, we highlight recent advancements in improving natural enzyme performance for terpene production across the three levels, present a generic workflow for multi-level optimization. Critically, this workflow is inherently iterative, as new bottlenecks emerge with increasing process complexity and scale. Accelerating this iterative development will be important to translating laboratory successes into commercially viable production systems.