XylR Mutant Enhances Xylose Utilization
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Solution Overview
Problem
Microbial systems for biofuel and chemical production using hydrolysate feedstocks face limitations due to the diauxic effect, where glucose inhibits the utilization of xylose, leading to lower yields and productivity.
Innovation Solution
Engineering a XylR protein variant with specific mutations at positions corresponding to SEQ ID NO:1, such as E382K, to enhance xylose utilization and co-utilization of glucose and xylose, allowing for improved growth and production of fatty acid derivatives in recombinant host cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If glucose is present in the culture medium, then glucose utilization is efficient, but xylose utilization is inhibited due to the diauxic effect
Solution Approach 1:
The patent applies parameter changes by introducing specific amino acid mutations in the XylR protein sequence (such as positions 83, 88, 89, 112, 120, 141, 145, 146, 147, 150, 154, 155, 247, 270, 280, 286, 289, 295, 305, 306, 313, 333, 336, 337, 351, 364, 365, 372, and 382) to alter the protein's regulatory parameters. These mutations change how XylR responds to glucose presence, enabling xylose utilization to proceed simultaneously with glucose metabolism rather than being inhibited, thus resolving the diauxic effect contradiction.
2Ease of manufacture
If hydrolysate feedstock is used instead of pure glucose, then production cost is reduced, but xylose utilization efficiency decreases
Solution Approach 1:
The patent modifies the XylR protein parameters through site-directed mutagenesis at specific positions to enhance its ability to activate xylose metabolism pathways. This allows the system to efficiently process xylose from hydrolysate feedstock, maintaining the cost advantage of using cheaper hydrolysates while improving xylose utilization rates to levels comparable to or exceeding pure glucose cultivation.
Solution Approach 2:
The engineered XylR protein acts as an intermediary that mediates between the presence of glucose and the utilization of xylose in hydrolysate feedstock. By modifying XylR's regulatory parameters, it enables the simultaneous activation of both glucose and xylose metabolic pathways, allowing the system to effectively process mixed sugar feedstocks without the traditional diauxic inhibition, thus bridging the gap between cost reduction and productivity maintenance.
Data Source
AI summary
The disclosure relates to mutant gene(s) that confer upon microorganisms that express them an improved capacity to utilize xylose and improved capacity to co-utilize glucose and xylose thereby resulting in improved growth of the microorganism. Further encompassed are methods of producing fatty acids and fatty acid derivatives from cellulosic biomass, xylose, and/or a glucose/xylose mix by employing the host cells expressing the engineered XylR variants and compositions of biologically produced fatty acids and fatty acid derivatives.