Production of muconic acid in plants

Aymerick Eudes,Roland Berthomieu,Zhangying Hao,Nanxia Zhao,Veronica Teixeira Benites,Edward E.K Baidoo,Dominique Loqué

doi:10.1016/j.ymben.2018.02.002

Abstract

Muconic acid (MA) is a dicarboxylic acid used for the production of industrially relevant chemicals such as adipic acid, terephthalic acid, and caprolactam. Because the synthesis of these polymer precursors generates toxic intermediates by utilizing petroleum-derived chemicals and corrosive catalysts, the development of alternative strategies for the bio-based production of MA has garnered significant interest. Plants produce organic carbon skeletons by harvesting carbon dioxide and energy from the sun, and therefore represent advantageous hosts for engineered metabolic pathways towards the manufacturing of chemicals. In this work, we engineered Arabidopsis to demonstrate that plants can serve as green factories for the bio-manufacturing of MA. In particular, dual expression of plastid-targeted bacterial salicylate hydroxylase (NahG) and catechol 1,2-dioxygenase (CatA) resulted in the conversion of the endogenous salicylic acid (SA) pool into MA via catechol. Sequential increase of SA derived from the shikimate pathway was achieved by expressing plastid-targeted versions of bacterial salicylate synthase (Irp9) and feedback-resistant 3-deoxy-D-arabino-heptulosonate synthase (AroG). Introducing this SA over-producing strategy into engineered plants that co-express NahG and CatA resulted in a 50-fold increase in MA titers. Considering that MA was easily recovered from senesced plant biomass after harvest, we envision the phytoproduction of MA as a beneficial option to add value to bioenergy crops.

Highlights

Muconic acid (MA) is a platform chemical that serves as a precursor for the synthesis of products such as adipic acid, terephthalic acid, and caprolactam which are widely used in the nylon and thermoplastic polymer industries
The plastidial salicylic acid (SA) pool derived from the shikimate pathway was used as precursor for the biosynthesis of MA in Arabidopsis stems
Since mature senesced Arabidopsis plants mainly consist of stem biomass, we selected two Arabidopsis promoters which are both strongly active in stem tissues that develop secondary cell walls for synchronized expression of nahG and catA (Fig. 1B)

Summary

Introduction

Muconic acid (MA) is a platform chemical that serves as a precursor for the synthesis of products such as adipic acid, terephthalic acid, and caprolactam which are widely used in the nylon and thermoplastic polymer industries. Most of the established biological routes consist in the production catechol and its subsequent conversion into MA by ring-cleaving catechol 1,2-dioxygenase (Vaillancourt et al, 2006) All these routes exploit the intrinsic shikimate pathway for the biosynthesis of catechol precursors such as protocatechuate, anthranilate, salicylic acid (SA), and 2,3-dihydroxybenzoic acid (Kruyer and Peralta-Yahya, 2017). MA biosynthetic pathways have been implemented in various microbial strains capable of growing in the presence of aromatics derived from lignocellulosic biomass. These include engineered strains of Escherichia coli (Sonoki et al, 2014; Wu et al, 2017), Amycolatopsis sp. These include engineered strains of Escherichia coli (Sonoki et al, 2014; Wu et al, 2017), Amycolatopsis sp. (Barton et al, 2017), Pseudomonas sp. (Vardon et al, 2015; Johnson et al, 2016, 2017; Sonoki et al, 2017), and Sphingobium sp. (Sonoki et al, 2017)

Methods

Results

Conclusion