Refactored Streptomyces Gene Clusters for Inducer-Independent Thaxtomin Production
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Solution Overview
Problem
The limited productivity and high cost of thaxtomin production in existing Streptomyces species, particularly the need for expensive inducers like cellobiose, hinder the industrial-scale production and commercialization of these potent herbicides.
Innovation Solution
Genetically engineered non-pathogenic Streptomyces bacteria are developed with refactored thaxtomin biosynthetic gene clusters, allowing them to produce thaxtomin compounds and intermediates in the absence of thaxtomin-inducing conditions such as cellobiose, using exogenous modules with linked promoters that control gene expression independently of traditional inducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional Streptomyces species are used for thaxtomin production, then thaxtomin can be produced, but high cost of inducers like cellobiose and low productivity limit industrial-scale production
Solution Approach 1:
The patent modifies the biosynthetic gene cluster by changing the promoter regulation parameters from inducer-dependent (cellobiose-induced) to constitutive or alternative inducer-dependent expression. This allows thaxtomin production without requiring expensive cellobiose inducers, thereby reducing production cost while maintaining or improving productivity through optimized gene expression parameters
Solution Approach 2:
The patent extracts and removes the dependency on expensive cellobiose inducers from the production system. By using alternative promoters that can be activated by cheaper inducers or work constitutively, the essential thaxtomin production function is maintained while the costly inducer requirement is extracted and eliminated from the process
2Productivity
If pathogenic Streptomyces strains are used, then thaxtomin production is achieved, but pathogenicity and need for expensive inducers constrain commercialization
Solution Approach 1:
The patent segments the thaxtomin biosynthetic gene cluster from the pathogenicity island, extracting only the thaxtomin production genes (txtA, txtB, txtC, txtD, txtE, txtH) while separating them from the pathogenicity determinants. This allows production of thaxtomin in non-pathogenic Streptomyces strains, eliminating the harmful pathogenicity factor while maintaining the desired productivity
Solution Approach 2:
The patent uses non-pathogenic Streptomyces strains as intermediary host organisms to express the thaxtomin biosynthetic gene cluster. These intermediary strains lack the pathogenicity factors but possess the metabolic machinery to produce thaxtomin, serving as safe alternatives for industrial production while maintaining production capability
Data Source
AI summary
The present disclosure includes refactored thaxtomin biosynthetic gene clusters including thaxtomin modules including one or more thaxtomin genes such that the expression of the refactored thaxtomin biosynthetic gene cluster produces at least one thaxtomin compound in the absence of thaxtomin-inducing conditions. Also included are genetically engineered Streptomyces bacterium from a non-pathogenic Streptomyces strain comprising an exogenous, refactored thaxtomin biosynthetic gene cluster of the present disclosure, such that the expression of the refactored thaxtomin biosynthetic gene cluster provides the genetically engineered Streptomyces bacterium with the ability to produce at least one thaxtomin compound in the absence of thaxtomin-inducing conditions. The present disclosure also includes methods of producing thaxtomin compounds, analogs, or intermediate with the refactored thaxtomin biosynthetic gene clusters and genetically engineered bacteria of the present disclosure.