Mutant Thioesterase Specificity for Octanoic Acid Production
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current microbial production of medium-chain fatty acids (MCFAs) faces challenges due to the lack of enzymes that are both highly active and selective towards medium chain-length substrates, leading to either high titers of MCFAs with mixed chain-lengths or low titers with narrow chain-length distribution.
Innovation Solution
Development of a mutant thioesterase with enhanced specificity and activity for C8 substrates, achieved through random mutagenesis of the Cuphea palustris FatB1 thioesterase and selection based on E. coli's lipoic acid requirement, resulting in a thioesterase that produces octanoic acid with >90% specificity and high titers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If native E. coli thioesterases (TesA and TesB) are overexpressed to control FFA chain length, then FFA production is achieved, but the substrate specificity is broad leading to mixed chain-length products requiring costly downstream separation
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues in the thioesterase active site (positions 65, 86, and 265) to alter substrate binding characteristics. The I65M, L86F, and L265F mutations collectively change the enzyme's parameter profile to preferentially bind C8 substrates, achieving >90% specificity for octanoic acid production while maintaining high productivity
2Manufacturing precision
If heterologous thioesterases with narrow chain-length specificity are expressed, then specific FFA chain length is achieved, but the catalytic activity and FFA titer remain low
Solution Approach 1:
The patent merges the advantageous properties of different thioesterases by combining the C8-specific substrate recognition features (derived from plant thioesterases like CpFatB1) with the high catalytic activity characteristics of E. coli TesA. The chimeric enzyme structure integrates the N-terminal region from CpFatB1 (providing specificity) with the C-terminal catalytic domain from TesA (providing activity), achieving both high titer and narrow specificity
3Manufacturing precision
If random mutagenesis is performed to improve substrate specificity, then enzyme specificity can be enhanced, but the process complexity and screening requirements increase
Solution Approach 1:
The patent applies local quality by focusing mutagenesis efforts on specific local regions of the enzyme that directly interact with the substrate. Rather than random whole-enzyme mutagenesis, the invention targets the active site residues (positions 65, 86, and 265) where local amino acid changes have the most significant impact on substrate specificity. This localized approach reduces the search space and simplifies the screening process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The mutant thioesterase demonstrates a significant increase in catalytic efficiency and achieves high titers of octanoic acid with high specificity, overcoming the limitations of existing microbial enzymes and enabling efficient microbial production of MCFAs.
Implementation Method 1
The specificity of the acyl-ACP thioesterase controls the terminal aliphatic chain length and chemical properties of the FFA product composition
Implementation Method 2
The mutant thioesterase demonstrates a significant increase in catalytic efficiency and achieves high titers of octanoic acid with high specificity
Data Source
AI summary
Mutant thioesterases having enhanced medium chain substrate activity, polynucleotides encoding and configured to express the mutant thioesterases in a transformed host cell, host cells transformed to contain the polynucleotides, and methods of using same.