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Maleate is one of the most important dicarboxylic acids and is used to produce various polymer compounds and pharmaceuticals. Herein, microbial production of maleate is successfully achieved, to our knowledge for the first time, using genetically modified Escherichia coli. A synthetic pathway of maleate is constructed in E. coli by combining the polyketide biosynthesis pathway and benzene ring cleavage pathway. The metabolic engineering approach used to fine-tune the synthetic pathway drastically improves maleate production and demonstrates that one of the rate limiting steps exists in the conversion of chorismate to gentisate. In a batch culture of the optimised transformant, grown in a 1-L jar fermentor, the amount of produced maleate reaches 7.1 g L−1, and the yield is 0.221 mol mol−1. Our results suggest that the construction of synthetic pathways by combining a secondary metabolite pathway and the benzene ring cleavage pathway is a powerful tool for producing various valuable chemicals.

Background The microbial production of useful fuels and chemicals has been widely studied. In several cases, glucose is used as the raw material, and almost all microbes adopt the Embden–Meyerhof (EM) pathway to degrade glucose into compounds of interest. Recently, the Entner–Doudoroff (ED) pathway has been gaining attention as an alternative strategy for microbial production. Results In the present study, we attempted to apply the ED pathway for isobutanol production in Escherichia coli because of the complete redox balance involved. First, we generated ED pathway-dependent isobutanol-producing E. coli . Thereafter, the inactivation of the genes concerning organic acids as the byproducts was performed to improve the carbon flux to isobutanol from glucose. Finally, the expression of the genes concerning the ED pathway was modified. Conclusions The optimized isobutanol-producing E. coli produced 15.0 g/L of isobutanol as the final titer, and the yield from glucose was 0.37 g/g (g-glucose/g-isobutanol). Electronic supplementary material The online version of this article (10.1186/s12934-019-1171-4) contains supplementary material, which is available to authorized users.

The effects of reinfusion of concentrated ascitic fluid may be maintained for 1 month, being potentially longer than that of total paracentesis alone. This study had no comparison groups and examined the short-term effect. A randomized controlled study to compare the long-term effects of total paracentesis alone vs. CART is necessary.

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To demonstrate that herbaceous biomass is a versatile gene resource, we focused on the model plant Brachypodium distachyon, and screened the B. distachyon for homologs of tyrosine decarboxylase (TDC), which is involved in the modification of aromatic compounds. A total of 5 candidate genes were identified in cDNA libraries of B. distachyon and were introduced into Saccharomyces cerevisiae to evaluate TDC expression and tyramine production. It is suggested that two TDCs encoded in the transcripts Bradi2g51120.1 and Bradi2g51170.1 have L-tyrosine decarboxylation activity. Bradi2g51170.1 was introduced into the L-tyrosine over-producing strain of S. cerevisiae that was constructed by the introduction of mutant genes that promote deregulated feedback inhibition. The amount of tyramine produced by the resulting transformant was 6.6-fold higher (approximately 200 mg/L) than the control strain, indicating that B. distachyon TDC effectively converts L-tyrosine to tyramine. Our results suggest that B. distachyon possesses enzymes that are capable of modifying aromatic residues, and that S. cerevisiae is a suitable host for the production of L-tyrosine derivatives.

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