Metabolic engineering of Rhodococcus jostii RHA1 for production of pyridine-dicarboxylic acids from lignin

• Published in: Microbial cell factories 2021-01, Vol.20 (1), p.15-15, Article 15
• Main Authors: Spence, Edward M, Calvo-Bado, Leonides, Mines, Paul, Bugg, Timothy D H
• Format: Article
• Language: English
• Subjects: Acids; Agricultural production; Analysis; Carbon; Carbon sources; Cellulose; Chromosomes; Dehydrogenases; Dicarboxylic acids; Engineering; Gene deletion; Gene expression; Gene promoter; Genes; Genetic modification; Genetic vectors; Insertion; Lignin; Lignin degradation; Lignocellulose; Metabolic engineering; Metabolism; Metabolites; Methods; Plasmids; Production processes; Protocatechuate 3,4-dioxygenase; Pyridine; Pyridine dicarboxylic acid; Pyridine-2,5-dicarboxylic acid; Pyridines; Raw materials; Rhodococcus; Rhodococcus jostii; Rhodococcus jostii RHA1; Soil microbiology; Straw; Syk protein; Testing; Wheat
• ISSN: 1475-2859; 1475-2859
• DOI: 10.1186/s12934-020-01504-z

Genetic modification of Rhodococcus jostii RHA1 was carried out in order to optimise the production of pyridine-2,4-dicarboxylic acid and pyridine-2,5-dicarboxylic acid bioproducts from lignin or lignocellulose breakdown, via insertion of either the Sphingobium SYK-6 ligAB genes or Paenibacillus praA gene respectively. Insertion of inducible plasmid pTipQC2 expression vector containing either ligAB or praA genes into a ΔpcaHG R. jostii RHA1 gene deletion strain gave 2-threefold higher titres of PDCA production from lignocellulose (200-287 mg/L), compared to plasmid expression in wild-type R. jostii RHA1. The ligAB genes were inserted in place of the chromosomal pcaHG genes encoding protocatechuate 3,4-dioxygenase, under the control of inducible P or P promoters, or a constitutive P promoter, producing 2,4-PDCA products using either wheat straw lignocellulose or commercial soda lignin as carbon source. Insertion of Amycolatopsis sp. 75iv2 dyp2 gene on a pTipQC2 expression plasmid led to enhanced titres of 2,4-PDCA products, due to enhanced rate of lignin degradation. Growth in minimal media containing wheat straw lignocellulose led to the production of 2,4-PDCA in 330 mg/L titre in 40 h, with > tenfold enhanced productivity, compared with plasmid-based expression of ligAB genes in wild-type R. jostii RHA1. Production of 2,4-PDCA was also observed using several different polymeric lignins as carbon sources, and a titre of 240 mg/L was observed using a commercially available soda lignin as feedstock.