Microbial Cell Factory for Efficiently Synthesizing Plant Natural Products via Optimizing the Location and Adaptation of Pathway on Genome Scale.

Bo Yang,Xudong Feng,Chun Li

doi:10.3389/fbioe.2020.00969

Abstract

Plant natural products (PNPs) possess important pharmacological activities and are widely used in cosmetics, health care products, and as food additives. Currently, most PNPs are mainly extracted from cultivated plants, and the yield is limited by the long growth cycle, climate change and complex processing steps, which makes the process unsustainable. However, the complex structure of PNPs significantly reduces the efficiency of chemical synthesis. With the development of metabolic engineering and synthetic biology, heterologous biosynthesis of PNPs in microbial cell factories offers an attractive alternative. Based on the in-depth mining and analysis of genome and transcriptome data, the biosynthetic pathways of a number of natural products have been successfully elucidated, which lays the crucial foundation for heterologous production. However, there are several problems in the microbial synthesis of PNPs, including toxicity of intermediates, low enzyme activity, multiple auxotrophic dependence, and uncontrollable metabolic network. Although various metabolic engineering strategies have been developed to solve these problems, optimizing the location and adaptation of pathways on the whole-genome scale is an important strategy in microorganisms. From this perspective, this review introduces the application of CRISPR/Cas9 in editing PNPs biosynthesis pathways in model microorganisms, the influences of pathway location, and the approaches for optimizing the adaptation between metabolic pathways and chassis hosts for facilitating PNPs biosynthesis.

Highlights

Plant natural products (PNPs) are secondary metabolites that are mainly used for defense and signal transduction in plants (Marienhagen and Bott, 2012)
With the rapid advances of synthetic biology, the production of PNPs in microbial cell factories has paved the way for large-scale industrial production by shortening the synthesis cycle and reducing the difficulty of product separation (Liu et al, 2017)
Numerous studies showed that the balance between endogenous and exogenous pathways contributed to the efficient synthesis of products (Zhang et al, 2015; Park et al, 2018), and the highest expression level of enzymes did not necessarily maximize the yield (Kang et al, 2018)

Summary

INTRODUCTION

Plant natural products (PNPs) are secondary metabolites that are mainly used for defense and signal transduction in plants (Marienhagen and Bott, 2012). This review covers recent studies on pathway location and strategies for optimizing the fitness and intracellular metabolism of the chassis cells to promote the production of PNPs. In 2013, the gene editing function of the CRISPR/Cas system was first verified in mammals (Cong et al, 2013). The CRISPR-mediated multi-locus gene integration strategy was developed to efficiently edit the β-carotene synthesis pathway in Saccharomyces cerevisiae (Ronda et al, 2015). Another significant research was that GTR-CPISPR could edit eight genes simultaneously with an efficiency up to 84% (Zhang Y. et al, 2019).

Method

Findings

CONCLUSION AND PERSPECTIVE