Streptococcus thermophilus gal-lac gene modification for high galactose utilization
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Solution Overview
Problem
Streptococcus thermophilus strains exhibit a galactose-negative phenotype, limiting their ability to efficiently utilize galactose in lactose-containing media, which is undesirable in dairy applications due to high galactose levels in final products.
Innovation Solution
Modifying the sequence of the gal-lac gene cluster in Streptococcus thermophilus strains to enhance galactose utilization, specifically introducing nucleic acid sequences like those defined by SEQ ID NO:2 or its derivatives, to achieve a 'high galactose utilization' profile, characterized by increased consumption rates and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Streptococcus thermophilus strains are used in dairy applications, then production efficiency is maintained, but galactose levels in final products become excessively high due to inability to utilize galactose
Solution Approach 1:
The patent modifies the gal-lac gene cluster sequence to change the metabolic parameters of S. thermophilus, enabling the bacteria to utilize galactose efficiently. This genetic modification alters the enzyme kinetics and metabolic pathway efficiency, transforming the strain from galactose-negative to high galactose utilization phenotype, thereby reducing galactose accumulation in dairy products.
Solution Approach 2:
The patent introduces modified gal-lac gene cluster sequences as genetic intermediaries that mediate between the bacterial cell machinery and galactose metabolism. These modified gene sequences encode enzymes with improved catalytic properties, acting as intermediaries to facilitate galactose utilization and prevent its accumulation in the final product.
2Quantity of substance
If galactose-positive mutants are selected under selective conditions, then galactose utilization ability is achieved, but the phenotype is unstable and rapidly lost when selective conditions are not maintained
Solution Approach 1:
The patent performs preliminary genetic modification of the gal-lac gene cluster sequence before strain deployment. By pre-modifying the gene sequence to optimize galactose metabolism, the strain is prepared in advance with stable high galactose utilization capability, eliminating the need for continuous selective pressure and preventing phenotype loss during subsequent cultivation.
Solution Approach 2:
The patent replaces unstable, transient galactose-positive mutants with genetically modified strains that have permanently altered gal-lac gene sequences. This substitution eliminates the need to continuously maintain selective conditions, as the modified strains inherently possess stable galactose utilization ability without requiring ongoing selection pressure.
3Stability of the object's composition
If conventional S. thermophilus strains are used, then strain stability is maintained, but galactose consumption is insufficient leading to high residual galactose in products
Solution Approach 1:
The patent changes the genetic parameters of S. thermophilus by modifying the gal-lac gene cluster sequence. This modification alters key metabolic parameters including enzyme activity, substrate affinity, and pathway flux, enabling the stable strain to consume galactose efficiently without losing its genetic and phenotypic stability.
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 modified strains demonstrate improved galactose utilization, reducing galactose levels in dairy products and meeting industry requirements for both production efficiency and product quality.
Implementation Method 1
The genes found in the gal operon encode a transcription regulator (galR), a galactokinase (galK), a galactose 1-phosphate uridyltransferase (galT), an UDP-glucose 4-epimerase (galE) and a mutarotase (galM). The enzymes encoded within this operon allows the utilization of galactose through the Leloir pathway
Data Source
AI summary
The invention relates to a method for generating a Streptococcus thermophilus strain exhibiting a “high galactose utilization” profile, which is characterized by a high percentage of consumed galactose at the maximum speed of lactose consumption and optionally a high percentage of consumed galactose at the end of lactose consumption (both as determined by assay I), comprising modifying the sequence of the gal-lac gene cluster. The invention also relates to a Streptococcus thermophilus strain obtained or obtainable by this method, to a Streptococcus thermophilus strain characterized both by the sequence of its gal-lac gene cluster and its “high galactose utilization” profile, to a culture and kit-of part comprising such strains, as well as to the use of such strains in food applications.