Engineered Polyketide Synthases for Delta-Lactone Production
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Solution Overview
Problem
Engineering polyketide synthases (PKS) to produce saturated β-carbon through reductive loop exchange has been challenging, particularly in designing partially reductive modules to generate delta-lactones, which are valuable for fragrances and industrial applications.
Innovation Solution
The method involves engineering lipomycin PKS by performing acyltransferase swaps and reductive loop swaps, specifically using BorAT and NanA2 modules, to programmably produce dimethylated, single-methylated, and nonmethylated delta-lactones, employing malonyl-CoA selecting analogs and full reductive loops in the second module, allowing for the production of delta-lactones of varying sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reductive loop exchange is performed to produce saturated β-carbon, then the ability to generate delta-lactones is improved, but the engineering difficulty and complexity increase significantly
Solution Approach 1:
The polyketide synthase is divided into modular domains (AT, KS, DH, ER, KR) that can be independently exchanged. The reductive loop is segmented into exchangeable domains that can be swapped between different PKS modules to achieve desired reduction states without redesigning the entire system.
Solution Approach 2:
The engineered PKS system achieves multi-functionality by incorporating domains that can produce multiple reduction states (saturated β-carbon, hydroxyl, ketone) within the same assembly line. The reductive loop domains serve universal functions across different modules, enabling production of diverse delta-lactone derivatives.
2Adaptability or versatility
If multiple acyltransferase swaps and reductive loop swaps are performed to produce various delta-lactones, then the product diversity is improved, but the manufacturing process complexity increases
Solution Approach 1:
The PKS system is designed with dynamic exchangeability of functional domains. Different AT and reductive loop domains can be programmed into the assembly line to dynamically adjust product output based on desired delta-lactone variants, enabling flexible production without rebuilding the entire system.
Solution Approach 2:
Product diversity is achieved by changing specific parameters (domain composition, reduction state, acyltransferase specificity) within the PKS system rather than creating entirely different pathways. This allows systematic variation of delta-lactone products through controlled parameter modification.
3Stability of the object's composition
If full reductive loop is used in the second module, then the saturation of β-carbon is improved, but the loss of natural product diversity occurs
Solution Approach 1:
Instead of applying full reduction uniformly across all modules, the system uses partial reduction in specific modules where needed. The reductive loop is strategically applied only in the second module to achieve saturated β-carbon for delta-lactone formation, while other modules retain their natural reduction states to preserve product diversity.
Data Source
AI summary
Polyketide synthases are engineered to produce lactones. In the first module, an acyltransferase is swapped and in the second module a reductive loop is swapped. With another acyltransferase swap in the second module, we can programmably produce the non-methylated delta lactone.