L-arginine Yield Improvement via Flavin Reductase Knockout
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Solution Overview
Problem
Current methods for producing L-arginine through microbial fermentation are low in yield and high in cost, with the existing strain Corynebacterium crenatum SDNN403 requiring improvements to meet domestic demands and reduce environmental impact.
Innovation Solution
Knocking out the NADPH-dependent FMN reductase genes frd1 and/or frd2 in Corynebacterium crenatum to enhance the yield of L-arginine by promoting anabolic flow and reducing oxidative stress, thereby increasing glucose utilization and production levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional mutagenesis method is used to obtain C. crenatum SDNN403, then the strain shows improved L-arginine production capability, but the production level and yield cannot meet domestic demands
Solution Approach 1:
The patent applies parameter changes by systematically modifying multiple genetic parameters simultaneously - knocking out four specific genes (proA, glnA, glnB, and frd2) to alter metabolic flux distribution. This multi-parameter optimization approach transformed the strain from producing 15.8 g/L to achieving 18.7 g/L L-arginine, resolving the contradiction between production level and yield by comprehensively optimizing genetic parameters rather than relying on traditional single-point mutagenesis
2Use of energy by moving object
If flavin reductase is active in C. crenatum, then electron transfer occurs, but H2O2 is produced which causes oxidative stress and damages cells
Solution Approach 1:
The patent applies the extraction principle by specifically removing the frd2 gene encoding flavin reductase from the C. crenatum genome. This extraction of the harmful component (flavin reductase that produces H2O2) eliminates the source of oxidative stress while preserving other essential metabolic functions. The knockout strategy selectively extracts only the problematic enzymatic activity, allowing the strain to maintain electron transfer efficiency through alternative pathways without generating toxic H2O2 byproducts
Solution Approach 2:
The patent converts the harmful effect of flavin reductase activity into a benefit by knocking out the frd2 gene. The elimination of H2O2-producing flavin reductase activity prevents oxidative damage to cells, thereby improving cell viability and L-arginine production. What was originally a harmful side effect (H2O2 production) is converted into a beneficial outcome (reduced oxidative stress and improved productivity) through targeted gene knockout
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 recombinant strain 403Δfrd1 and 403Δfrd2 show increased L-arginine yields by 16.46% and 3.16%, respectively, with 18.4 g/L and 16.3 g/L production after 60 hours of fermentation, addressing the limitations of traditional methods.
Implementation Method 1
flavin reductases can be used for reducing oxidized flavins FMN and FAD as well as riboflavin into reduced flavins FMNH2 and FADH2 as well as reduced riboflavin by utilizing NAD(P)H
Implementation Method 2
superoxide dismutase can be used for converting the superoxide anions O2− into H2O2
Implementation Method 3
catalase can be used for decomposing H2O2 into H2O and O2
Data Source
AI summary
The invention discloses a method for increasing the yield of L-arginine by knocking out flavin reductases, and belongs to the technical field of amino acid production by microbial fermentation. Genes frd1 and frd2 for encoding hypothetic NADPH-dependent FMN reductase in Corynebacterium crenatum SDNN403 are over-expressed in E. coli BL21 and are purified to form target proteins Frd181 and Frd188, and functions of the target proteins are identified to obtain a result showing that the proteins Frd181 and Frd188 both are NAD(P)H-dependent flavin reductases producing H2O2. By taking a genome of the Corynebacterium crenatum SDNN403 as a template, frd1 and frd2 gene deletion fragments are obtained by overlap extension PCR; connecting pK18mobsacB to obtain knockout plasmids pK18mobsacB-Δfrd1 and pK18mobsacB-Δfrd2; carrying out electric shock to transform the Corynebacterium crenatum SDNN403; and carrying out secondary screening to obtain recombinant strains 403Δfrd1 and 403Δfrd2. Found by flask shaking fermentation, the yield of L-arginine is obviously increased by knocking out the genes frd1 and frd2.