Microbial Conversion of Rebaudioside A to D and M
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Solution Overview
Problem
Current methods for producing Rebaudioside D and Rebaudioside M, which have superior taste properties compared to Rebaudioside A, are inefficient due to the rarity of these compounds in nature and the instability and cost of UDP-glucose, a necessary co-substrate for UDP-glycosyl transferases.
Innovation Solution
A method involving a host cell capable of taking up Rebaudioside A, regenerating UDP-glucose, and expressing UDP-glucosyl transferase enzymes to convert Rebaudioside A into Rebaudioside D and Rebaudioside M, using microbial species like Kluyveromyces marxianus that are safe for food use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UDP-glycosyl transferases are used to convert Rebaudioside A to Rebaudioside D and Rebaudioside M, then superior taste properties are achieved, but the process becomes inefficient due to the instability and high cost of UDP-glucose co-substrate
Solution Approach 1:
The host cell is engineered to autonomously regenerate UDP-glucose from glucose-1-phosphate using engineered enzymes (phosphoglucomutase and UDP-glucose pyrophosphorylase), eliminating the need for external addition of expensive and unstable UDP-glucose. The cell's metabolic pathway is harnessed to continuously supply the required co-substrate.
Solution Approach 2:
Glucose-1-phosphate serves as an intermediary substance that is stable and inexpensive to produce, which is then converted by engineered enzymes into UDP-glucose in situ. This intermediary approach bypasses the problems of directly using unstable and costly UDP-glucose.
2Manufacturing precision
If Rebaudioside D and Rebaudioside M are produced through natural occurrence, then high purity sweeteners are obtained, but the production is limited due to the rarity of these compounds in nature
Solution Approach 1:
The invention extracts and utilizes only the essential genetic elements (UGT enzyme genes and UDP-glucose regeneration pathway genes) from natural sources and transfers them into a controllable host cell system. This allows production to be decoupled from natural rarity while maintaining the enzymatic specificity required for high purity product formation.
Solution Approach 2:
The host cell's metabolic parameters are optimized through genetic engineering to favor the production of Rebaudioside D and Rebaudioside M. Expression levels of UGT enzymes and UDP-glucose regeneration enzymes are tuned to maximize conversion efficiency and product purity while maintaining cell viability.
3Reliability
If microbial species are selected for food safety, then safe sweeteners are produced, but the ability to assimilate Rebaudioside A and regenerate UDP-glucose may be limited
Solution Approach 1:
The metabolic pathway is segmented into distinct functional modules: Rebaudioside A uptake system, UDP-glucose regeneration module (using phosphoglucomutase and UDP-glucose pyrophosphorylase), and glycosylation module (using UGT enzymes). Each module can be independently optimized and assembled in safe microbial hosts.
Solution Approach 2:
The host cell is engineered to perform multiple functions: taking up Rebaudioside A, regenerating UDP-glucose from glucose-1-phosphate, and catalyzing the glycosylation reactions. This multi-functionality is achieved by introducing complementary genetic pathways into a single safe microbial platform.
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
This method enables efficient intracellular conversion of Rebaudioside A to Rebaudioside D and Rebaudioside M, overcoming the limitations of natural availability and co-substrate stability, thereby enhancing the production of these valuable sweeteners.
Implementation Method 1
subjecting rebaudioside A to a UDP-glucosyl transferase enzyme, the UDP-glucosyl transferase enzyme is intracellularly produced by a host cell
Implementation Method 2
the host cell is capable of rebaudioside A uptake from a culture medium
Data Source
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AI summary
A method of producing steviol glycoside compositions and the use thereof in foods, beverages and other consumables, is described.