Reconstruction of metabolic pathway for isobutanol production in Escherichia coli.

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).

Efficacy and safety of reinfusion of concentrated ascitic fluid for malignant ascites: a concept-proof study.

PURPOSE: Malignant ascites is one of the symptoms causing discomfort in advanced cancer patients. Cell-free and concentrated ascites reinfusion therapy (CART) is one treatment modality, but controlled trials are limited. The primary aim of this study was to explore the efficacy and safety of CART, as well as their predictors, to obtain data for planning a further controlled trial. METHODS: This was a single center retrospective cohort study in patients with refractory malignant ascites. Consecutive adult patients who underwent CART were enrolled. The primary endpoints were the time to next paracentesis and seven patient-reported symptoms (e.g., abdominal pain and distension). The secondary endpoints were adverse events, laboratory findings, and physical findings. RESULTS: A total of 104 CART procedures for 51 patients were analyzed. The median time to next paracentesis was 27 days (95% CI, 21-35). Intensities of all seven symptoms were significantly improved after CART (p < 0.0001 for all symptoms). Grade 3 hypotension occurred during one procedure, and mild fever occurred in 5%. Total protein, albumin, and estimated glomerular filtration rate were significantly increased. Hemorrhagic ascites, ascites white blood cell count, serum total protein, and lymphocyte percentages were the independent predictors of the time to next paracentesis. CONCLUSION: 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.

Engineering a synthetic pathway for maleate in Escherichia coli.

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.

Metabolic design of a platform Escherichia coli strain producing various chorismate derivatives.

A synthetic metabolic pathway suitable for the production of chorismate derivatives was designed in Escherichia coli. An L-phenylalanine-overproducing E. coli strain was engineered to enhance the availability of phosphoenolpyruvate (PEP), which is a key precursor in the biosynthesis of aromatic compounds in microbes. Two major reactions converting PEP to pyruvate were inactivated. Using this modified E.coli as a base strain, we tested our system by carrying out the production of salicylate, a high-demand aromatic chemical. The titer of salicylate reached 11.5 g/L in batch culture after 48 h cultivation in a 2-liter jar fermentor, and the yield from glucose as the sole carbon source exceeded 40% (mol/mol). In this test case, we found that pyruvate was synthesized primarily via salicylate formation and the reaction converting oxaloacetate to pyruvate. In order to demonstrate the generality of our designed strain, we employed this platform for the production of each of 7 different chorismate derivatives. Each of these industrially important chemicals was successfully produced to levels of 1-3g/L in test tube-scale culture.

Evaluation of Brachypodium distachyon L-Tyrosine Decarboxylase Using L-Tyrosine Over-Producing Saccharomyces cerevisiae.

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.

Accelerated evolution of fetuin family proteins in Protobothrops flavoviridis (habu snake) serum and the discovery of an L1-like genomic element in the intronic sequence of a fetuin-encoding gene.

Habu serum factor (HSF) and HSF-like protein (HLP) are fetuin family proteins isolated from Protobothrops flavoviridis (habu snake) serum with different physiological activities. A comparison of their cDNAs and intronic sequences revealed that nucleotide substitutions were primarily in protein-coding regions, and the substitution patterns indicated accelerated evolution of these proteins. Genomic DNA fragment analysis, including intron 1, revealed a 6.6-kb insertion homologous to the full-length mammalian LINE1 (L1) retrotransposable element (PfL1) only in the HLP gene. This segment retains an open reading frame (ORF) that encodes a reverse transcriptase (RT)-like protein (PfRT). We further found that a large number of homologous segments have dispersed in the habu snake genome, although we could not determine the enzymatic activities of their products. Moreover, an analysis of habu snake liver RNA indicated active transcription of the PfRT genes, suggesting that high levels of RT activity in this snake have driven the evolution of unique phenotypes of venom enzymes and serum inhibitors of them.