Removal of contaminated organic acids from simulated succinic acid fermentation broth by reactive extraction process: Single- and mixed-solute solution

This work aims to study how to remove the organic acid by-products from simulated fermentation broth containing succinic acid by reactive extraction. Model solutions including single-, binary-, ternary-, and quaternary-solute solutions were used. The broths were reactively extracted using 0.25 mol TOA/kg 1-octanol under pH of 2.45-6.0. The extracted broths were then distillated under vacuum -0.017 MPa with operating temperature between 45 and 65°C. Finally, the distilled broths were crystallized at 4°C and pH of 2.0. The results showed that the purity and yield of succinic acid of 99.10% and 30.25%, respectively, were obtained.     

Synthesis of Nicotinamide Mononucleotide from Xylose via Coupling Engineered Escherichia coli and a Biocatalytic Cascade

β-Nicotinamide mononucleotide (NMN) has recently gained attention for a nutritional supplement because it is an intermediate in the biosynthesis of nicotinamide adenine dinucleotide (NAD⁺). In this study, we developed NMN synthesis by coupling two modules. The first module is to culture E. coli MG1655 ▵tktA ▵tktB ▵ptsG to metabolize xylose to generate D-ribose in the medium. The supernatant containing D-ribose was applied in the second module which is composed of EcRbsK-EcPRPS-CpNAMPT reaction to synthesize NMN, that requires additional enzymes of CHU0107 and EcPPase to remove feedback inhibitors ADP and pyrophosphate. The second module can be rapidly optimized by comparing NMN production determined by the cyanide assay. Finally, 10 mL optimal biocascade reaction generated NMN with a good yield of 84 % from 1 mM D-ribose supplied from the supernatant of E. coli MG1655 ▵tktA ▵tktB ▵ptsG. Our results can further guide researchers to metabolically engineer E. coli for NMN synthesis.