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Updated: May 31, 2026
Mutagenesis and Functional Selection Protocols for Directed Evolution of Proteins in E. coli
Published on: March 16, 2011
Programming a bacterial biosensor for directed evolution of tryptophan hydroxylase via high-throughput droplet
Huimin Li1, Wei Zhang1, Yuying Han1
1Key Laboratory of Industrial Fermentation Microbiology of the Ministry of Education, Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, National Engineering Laboratory for Industrial Enzymes, Tianjin, 300457, PR China.
Researchers engineered a bacterial biosensor and droplet screening platform to enhance tryptophan hydroxylase (TPH) for 5-hydroxytryptophan (5-HTP) production. A superior M4-1 TPH variant showed a 4.25-fold activity increase and improved thermostability.
Area of Science:
- Biotechnology
- Enzyme Engineering
- Synthetic Biology
Background:
- Tryptophan hydroxylase (TPH) modification is key for 5-hydroxytryptophan (5-HTP) biosynthesis.
- Industrial enzyme properties require significant improvement for efficient production.
Purpose of the Study:
- To develop a droplet-based ultrahigh-throughput microfluidic screening platform (DTSP) for TPH improvement.
- To engineer a sensitive bacterial biosensor for L-tryptophan (L-Trp) detection.
- To screen and identify superior TPH mutants with enhanced industrial properties.
Main Methods:
- Established a droplet-based ultrahigh-throughput microfluidic screening platform (DTSP).
- Engineered a bacterial biosensor utilizing promoter pJ23111 for L-Trp detection.
- Employed iterative saturation mutagenesis (ISM) for TPH mutant screening on the DTSP platform.
Main Results:
- The bacterial biosensor demonstrated a negative correlation between L-Trp concentration and fluorescence.
- The M4-1 TPH variant exhibited a 4.25-fold increase in catalytic activity compared to the parent.
- The M4-1 variant showed enhanced thermostability, with a 3.2-fold longer half-life at 45°C.
Conclusions:
- The optimized DTSP and biosensor system effectively screened for superior TPH mutants.
- The engineered M4-1 TPH variant presents significant improvements in activity and stability.
- This study offers a valuable framework for developing bacterial biosensors in microdroplet screening applications.
