PEP Synthase Attenuation for Cysteine Fermentation Yield
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Solution Overview
Problem
Current methods for fermentative production of L-cysteine do not achieve high enough yields to be economically viable due to limitations in enzyme activity and product accumulation within microorganisms, leading to inefficiencies in fermentation processes.
Innovation Solution
A microorganism strain with reduced or inactivated phosphoenolpyruvate synthase (PEP synthase) enzyme activity, encoded by the ppsA gene, is developed to enhance L-cysteine production by modifying the genetic makeup of strains like Escherichia coli and Pantoea ananatis, allowing for increased yields of L-cysteine and its derivative L-cystine through optimized metabolic pathways and fermentation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wild-type PEP synthase enzyme activity is maintained in the microorganism strain, then normal metabolic function is preserved, but L-cysteine production yield remains low
Solution Approach 1:
The patent applies parameter changes by modifying the ppsA gene to alter the enzyme activity level of PEP synthase. By creating mutant variants with reduced activity (e.g., 10-50% of wild-type activity) or complete inactivation, the metabolic flux is redirected toward L-cysteine production while maintaining sufficient PEP synthase function for basic metabolism, thereby resolving the contradiction between productivity improvement and metabolic stability
2Productivity
If PEP synthase enzyme activity is completely inactivated to maximize L-cysteine production, then product yield increases, but cell survival and metabolic balance are compromised
Solution Approach 1:
The patent implements partial action by reducing PEP synthase activity to a specific range (10-50% of wild-type activity) rather than complete inactivation. This partial reduction is sufficient to redirect metabolic flux toward L-cysteine production while leaving enough enzymatic activity to maintain essential metabolic functions and cell viability, thus avoiding the harmful effects of complete enzyme inactivation
3Ease of manufacture
If traditional fermentation methods are used with wild-type strains, then process simplicity is maintained, but economic viability is insufficient due to low yields
Solution Approach 1:
The patent modifies the genetic parameter of the microorganism by introducing ppsA gene mutations that reduce PEP synthase activity. This genetic parameter change leads to increased L-cysteine production yields (up to 2-3 times higher than wild-type strains), thereby improving economic viability while maintaining the simplicity of the fermentation process itself, as no complex additional process steps are required
Data Source
AI summary
Genetically modified microorganism strains for the fermentative production of cysteine provide higher yields of L-cysteine or L-cystine during fermentation. Cysteine production is improved in the genetically modified microorganism strains by attenuating or inactivating phosphoenolpyruvate synthase enzyme activity, alone or in combination with the overexpression of efflux proteins and proteins that reduce feedback inhibition by cysteine and by serine.