Microbial Platform for Terpenoid Production: Escherichia coli and Yeast

Abstract

Terpenoids, also called isoprenoids, are a large and highly diverse family of natural products with important medical and industrial properties. However, a limited production of terpenoids from natural resources constrains their use of either bulk commodity products or high valuable products. Microbial production of terpenoids from Escherichia coli and yeasts provides a promising alternative owing to available genetic tools in pathway engineering and genome editing, and a comprehensive understanding of their metabolisms. This review summarizes recent progresses in engineering of industrial model strains, E. coli and yeasts, for terpenoids production. With advances of synthetic biology and systems biology, both strains are expected to present the great potential as a platform of terpenoid synthesis.

Keywords: Escherichia coli; MEP pathway; MVA pathway; strain engineering; synthetic biology; terpenoid; yeast.

FIGURE 1

Overview of terpenoids biosynthesis pathway (A), and pathway engineering strategies (B,C). Terpenoids biosynthesis is comprised of carbon assimilation, isoprene unit synthesis, terpenoids backbone synthesis, and terpenoids decoration. C₆ or C₅ sugar enters the central pathway of glycolysis. MEP and MVA pathways use central metabolites to initiate synthesis of IPP and DMAPP, the building blocks of terpenoids. Terpenoid synthesis pathways could be assembled and engineered in a tractable host (e.g., E. coli or yeasts) to create cell factories for their mass production. Two fashions of static and dynamic engineering have been used to optimize the synthesis pathways and coordinate them with host metabolic network. Static engineering approach generally constructs a matrix of genes, promoters, and regulatory elements (e.g., UTRs) to screen the best orchestra, while dynamic engineering approach relies on biosensors (metabolite response or transcription factor-based) to dynamically control the synthesis pathway. The red dots present the key intermediates of terpenoid biosynthesis, and the yellow and cyan dots present primary terpenenoids and decorated terpenoids, respectively (A,B). TF presents transcription factor (C).

FIGURE 2

Strain manipulation by genome editing (A), integrated-omics (B), and consortia process (C). Host genome can be evolved by either random (e.g., MAGE) or rational engineering (e.g., Cas9-CRISPR). The integrated-omics approaches can comprehensively elucidate host metabolism, which benefit strain manipulation. The microbial consortia process divides a long complicated pathway into a few short simple pathways, dispersed among microbes in the consortia. It can be built in the same species (homo-consortia) or the different species (hetero-consortia).