Recombinant Yeast Nitrogen Assimilation for Ethanol Yield
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Solution Overview
Problem
Current strategies for reducing glycerol production in ethanol fermentation by yeast, such as engineering ammonia fixation or overexpressing certain enzymes, either partially reduce glycerol formation or create by-products, failing to achieve industrially relevant yields and fermentation rates.
Innovation Solution
A recombinant microorganism with engineered genetic modifications that up-regulate or down-regulate enzymes in ethanol production, glycerol-production, and nitrogen-assimilation pathways, specifically targeting enzymes like glutamate dehydrogenase, glycerol-3-phosphate dehydrogenase, and pyruvate formate lyase to optimize ethanol yield and reduce glycerol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If current strategies for reducing glycerol production (engineering ammonia fixation or overexpressing certain enzymes) are used, then glycerol formation is partially reduced, but ethanol yield and fermentation rate remain insufficient for industrial relevance
Solution Approach 1:
The patent applies parameter changes by systematically modifying multiple genetic parameters simultaneously - deleting GDH1 gene, overexpressing GLT1 and GLN1 genes, and engineering nitrogen assimilation pathways. This multi-parameter approach transforms the metabolic state of the yeast to achieve both reduced glycerol formation (10-100% reduction) and maintained high ethanol productivity, resolving the contradiction between substance loss reduction and productivity maintenance
Solution Approach 2:
The patent introduces nitrogen assimilation pathway enzymes (glutamate synthase GLT1 and glutamine synthetase GLN1) as intermediary components that mediate between carbon metabolism and nitrogen metabolism. These intermediaries redirect metabolic flux away from glycerol production while maintaining ethanol production, acting as bridges that协调 the conflicting requirements of reduced glycerol and sustained ethanol yield
2Speed
If nitrogen sources (ammonium, amino acids, urea) are added to promote yeast growth, then fermentation kinetics improve, but ethanol yield decreases due to excess biomass and glycerol formation
Solution Approach 1:
The patent implements feedback control through engineered nitrogen assimilation pathways that respond to cellular metabolic state. The overexpressed GLT1 and GLN1 enzymes provide feedback mechanisms that regulate nitrogen uptake and assimilation based on cellular needs, preventing excess nitrogen from being converted to glycerol while maintaining optimal fermentation kinetics. This feedback system allows the yeast to efficiently utilize nitrogen without the harmful side effect of increased glycerol formation
Solution Approach 2:
The patent changes the metabolic parameters of nitrogen assimilation by overexpressing specific enzymes (GLT1, GLN1) and deleting others (GDH1), fundamentally altering how nitrogen is processed. This parameter change enables the system to maintain fast fermentation kinetics while converting nitrogen more efficiently into biomass precursors rather than glycerol, thereby preventing ethanol yield loss
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 recombinant microorganism achieves higher ethanol yields and lower glycerol production, with ethanol titers increased by 1-10% and glycerol titers reduced by 10-100% compared to unmodified strains, enhancing fermentation efficiency.
Implementation Method 1
the fermentation of hexose sugars (e.g., glucose, mannose, and galactose); and (4) the fermentation of pentose sugars (e.g., xylose and arabinose)
Implementation Method 2
at least one engineered genetic modification that leads to the up-regulation or down-regulation of one or more native and/or heterologous enzymes that function in one or more ethanol production pathways
Data Source
AI summary
The present invention provides for a mechanism to reduce glycerol production and increase nitrogen utilization and ethanol production of recombinant microorganisms. One aspect of this invention relates to strains of S. cerevisiae with reduced glycerol productivity that get a kinetic benefit from higher nitrogen concentration without sacrificing ethanol yield. A second aspect of the invention relates to metabolic modifications resulting in altered transport and/or intracellular metabolism of nitrogen sources present in corn mash.