Format

Send to

Choose Destination
Metab Eng. 2018 May;47:279-293. doi: 10.1016/j.ymben.2018.03.003. Epub 2018 Mar 14.

From lignin to nylon: Cascaded chemical and biochemical conversion using metabolically engineered Pseudomonas putida.

Author information

1
Institute of Systems Biotechnology, Saarland University, Germany.
2
Leibniz Institute for Agricultural Engineering and Bioeconomy, Potsdam, Germany.
3
Leibniz Institute for Agricultural Engineering and Bioeconomy, Potsdam, Germany; Institute of Sustainable and Environmental Chemistry (ISEC), Leuphana University of Lüneburg, Germany.
4
Kekulé-Institute for Organic Chemistry and Biochemistry, University of Bonn, Germany.
5
Institute of Systems Biotechnology, Saarland University, Germany. Electronic address: christoph.wittmann@uni-saarland.de.

Abstract

Cis,cis-muconic acid (MA) is a chemical that is recognized for its industrial value and is synthetically accessible from aromatic compounds. This feature provides the attractive possibility of producing MA from mixtures of aromatics found in depolymerized lignin, the most underutilized lignocellulosic biopolymer. Based on the metabolic pathway, the catechol (1,2-dihydroxybenzene) node is the central element of this type of production process: (i) all upper catabolic pathways of aromatics converge at catechol as the central intermediate, (ii) catechol itself is frequently generated during lignin pre-processing, and (iii) catechol is directly converted to the target product MA by catechol 1,2-dioxygenase. However, catechol is highly toxic, which poses a challenge for the bio-production of MA. In this study, the soil bacterium Pseudomonas putida KT2440 was upgraded to a fully genome-based host for the production of MA from catechol and upstream aromatics. At the core of the cell factories created was a designed synthetic pathway module, comprising both native catechol 1,2-dioxygenases, catA and catA2, under the control of the Pcat promoter. The pathway module increased catechol tolerance, catechol 1,2-dioxygenase levels, and catechol conversion rates. MA, the formed product, acted as an inducer of the module, triggering continuous expression. Cellular energy level and ATP yield were identified as critical parameters during catechol-based production. The engineered MA-6 strain achieved an MA titer of 64.2 g L-1 from catechol in a fed-batch process, which repeatedly regenerated the energy levels via specific feed pauses. The developed process was successfully transferred to the pilot scale to produce kilograms of MA at 97.9% purity. The MA-9 strain, equipped with a phenol hydroxylase, used phenol to produce MA and additionally converted o-cresol, m-cresol, and p-cresol to specific methylated variants of MA. This strain was used to demonstrate the entire value chain. Following hydrothermal depolymerization of softwood lignin to catechol, phenol and cresols, MA-9 accumulated 13 g L-1 MA and small amounts of 3-methyl MA, which were hydrogenated to adipic acid and its methylated derivative to polymerize nylon from lignin for the first time.

KEYWORDS:

Bionylon; Catechol; Catechol dioxygenase; Cis,cis-muconic acid; Cresol; Funneling; Hydrothermal conversion; Lignin; Methyl adipic acid; Methyl muconic acid, adipic acid; Nylon 6,6; Phenol; Phenol hydroxylase; Pseudomonas putida; Synthetic promoter library

PMID:
29548984
DOI:
10.1016/j.ymben.2018.03.003
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center