L-Tryptophan (Trp) is a high-value aromatic amino acid with diverse applications in food and pharmaceutical industries. Although production of Trp by engineered has been extensively studied, the need of multiple precursors for its synthesis and the complex regulations of the biosynthetic pathways make the achievement of a high product yield still very challenging. Metabolic flux analysis suggests that the use of a phosphoenolpyruvate:sugar phosphotransferase system (PTS) independent glucose uptake system, i.e. the galactose permease/glucokinase (GalP/Glk) system, can theoretically double the Trp yield from glucose. To explore this possibility, a PTS and GalP/Glk-dependent strain was constructed from a previously rationally developed Trp producer strain S028. However, the growth rate of the S028 mutant was severely impaired. To overcome this problem, promoter screening for modulated gene expression of GalP/Glk was carried out, following by a batch mode of adaptive laboratory evolution (ALE) which resulted in a strain K3 with a similar Trp yield and concentration as S028. In order to obtain a more efficient Trp producer, a novel continuous ALE system was developed by combining CRISPR/Cas9-facilitated mutagenesis with real-time measurement of cell growth and online monitoring of Trp-mediated fluorescence intensity. With the aid of this automatic system (auto-CGSS), a promising strain T5 was obtained and fed-batch fermentations showed an increase of Trp yield by 19.71% with this strain compared with that obtained by the strain K3 (0.164 vs. 0.137 g/g). At the same time, the specific production rate was increased by 52.93% (25.28 vs. 16.53 mg/g /h). Two previously engineered enzyme variants AroG and TrpC were integrated into the strain T5, resulting in a highly productive strain T5AA with a Trp yield of 0.195 g/g and a specific production rate of 28.83 mg/g /h.
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http://dx.doi.org/10.1016/j.mec.2021.e00167 | DOI Listing |
Animals (Basel)
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College of Food Science and Technology, Shanghai Ocean University, Shanghai 201306, China.
Live fish transportation plays a crucial role in the commercial fish trade. Consequently, mitigating stress during transportation is essential for enhancing the survival rate of fish and reducing potential financial losses. In this study, the effectiveness was evaluated of exogenous tryptophan in reducing transport stress in hybrid grouper, ♀ × ♂.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2025
Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Zhang Jiang Institute for Advanced Study, Shanghai Jiao Tong University, Shanghai 200240, China.
Class II photolyases (PLs) are a distant subclade in the photolyase/cryptochrome superfamily, displaying a unique Trp-Tyr tetrad for photoreduction and exhibiting a lower quantum yield (QY) of DNA repair (49%) than class I photolyases (82%) [M. Zhang, L. Wang, S.
View Article and Find Full Text PDFACS Omega
December 2024
Universidade do Extremo Sul Catarinense (UNESC), Av. Universitária, 1105, Criciúma CEP 88806-000, SC, Brazil.
This study describes the synthesis of new carboxylated merocyanine dyes by Knoevenagel condensation between 4-carboxybenzaldehyde and indolium/benzoindolium- and benzothiazolium-based coupling compounds. The condensations were performed in the presence of ammonium acetate, and the products were obtained in good yields after simple purification. These merocyanines exhibit UV-A-to-blue absorption and blue-to-green fluorescence emission, characterized by relatively large Stokes shift values (∼5000 cm).
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College of Forensic Medicine, Hebei Medical University, Hebei Key Laboratory of Forensic Medicine, Collaborative Innovation Center of Forensic Medical Molecular Identification, Research Unit of Digestive Tract Microecosystem Pharmacology and Toxicology, Chinese Academy of Medical Sciences, Shijiazhuang, Hebei Province 050017, PR China; Key Laboratory of Neural and Vascular Biology, Ministry of Education, Shijiazhuang, Hebei Province 050017, PR China. Electronic address:
Front Plant Sci
November 2024
Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
Recently, due to the widespread use of the acetolactate synthase (ALS)-inhibiting herbicide penoxsulam in paddy fields in China, (L.) P. Beauv.
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