Recombinant Yeast Lipid Production via Xpk/Pta Pathway
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Solution Overview
Problem
Microbial cells, such as yeast, face challenges in lipid production due to the high glucose requirements of native fatty acid synthesis pathways, leading to environmental concerns from plant oil feedstocks and inefficiencies in glucose-to-lipid conversion.
Innovation Solution
Recombinant yeast cells expressing functional phosphoketolase and phosphotransacetylase proteins, optimized for reduced glucose consumption through the Xpk/Pta pathway, are engineered to enhance lipid production by modifying gene expression and pathway flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the native fatty acid synthesis pathway is used in yeast cells, then lipid production can be achieved, but glucose consumption is excessively high requiring 18 glucose molecules to produce one triolein molecule
Solution Approach 1:
The patent divides the lipid synthesis pathway into two distinct routes: the native glycolysis-dependent pathway and a heterologous Xpk/Pta pathway that uses the pentose phosphate pathway instead. This segmentation allows the cell to choose an alternative route that consumes fewer glucose molecules (2.3 fewer per triolein) while producing the same lipid product.
Solution Approach 2:
The patent introduces heterologous phosphoketolase (Xpk) and phosphotransacetylase (Pta) enzymes as intermediary catalysts that enable the alternative pathway. These enzymes mediate the conversion of pentose phosphate pathway intermediates to acetyl-CoA, bypassing the glucose-intensive glycolysis pathway and reducing overall glucose consumption by 2.3 molecules per triolein produced.
2Productivity
If the Xpk/Pta pathway is implemented in E. coli to reduce glucose consumption, then lipid production efficiency improves, but the system requires 11 gene overexpressions, 9 gene deletions, and over 50 genomic mutations to function
Solution Approach 1:
The patent extracts and expresses only the two essential heterologous genes (Xpk and Pta) in yeast cells, eliminating the need for the extensive genetic modifications required in E. coli. By selecting a yeast host with more favorable metabolic compatibility, the system achieves the same lipid production efficiency improvement without requiring 11 gene overexpressions, 9 deletions, and 50+ mutations.
Solution Approach 2:
The patent changes the host organism parameter from E. coli to yeast (Saccharomyces cerevisiae or Yarrowia lipolytica), which has different metabolic characteristics that are more compatible with the Xpk/Pta pathway. This parameter change reduces the genetic engineering complexity from over 70 modifications to just two heterologous gene expressions, while maintaining improved lipid production efficiency.
3Quantity of substance
If plant oil feedstocks are used to fulfill industry demands, then lipid supply is sufficient, but environmental harm increases due to forest displacement and biodiversity loss
Solution Approach 1:
The patent enables yeast cells to synthesize lipids de novo from simple carbon sources through the engineered Xpk/Pta pathway, making the system self-sufficient and independent of plant oil feedstocks. This eliminates the need for agricultural plantations that displace forests and harm biodiversity, while still providing sufficient lipid supply for industrial applications.
Solution Approach 2:
The patent introduces heterologous phosphoketolase and phosphotransacetylase enzymes as intermediaries that enable yeast to convert pentose phosphate pathway intermediates into acetyl-CoA for lipid synthesis. This intermediary pathway allows microbial cells to produce lipids efficiently without requiring plant oil feedstocks, thereby eliminating the environmental harm associated with agricultural expansion.
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 yeast cells demonstrate improved lipid yields and productivity, overcoming growth and lipid production deficits of wild-type cells while reducing glucose dependency, thus addressing environmental and efficiency concerns.
Implementation Method 1
phosphoketolase (Xpk, EC 4.1.2.9, EC 4.1.2.22), which converts fructose 6-phosphate (F6P) and/or the PPP intermediate xylulose 5-phosphate (X5P) to acetyl phosphate (AcP) and glyceraldehyde 3-phosphate (Ga3P)
Implementation Method 2
phosphotransacetylase (Pta, EC 2.3.1.8), which catalyzes the reversible conversion of AcP to acetyl-CoA
Implementation Method 3
recombinant yeast cells expressing functional phosphoketolase and phosphotransacetylase proteins, optimized for reduced glucose consumption through the Xpk/Pta pathway
Data Source
AI summary
Aspects of the disclosure are directed to genetically modified yeast cells and methods for use. Certain aspects are directed to recombinant yeast cells comprising exogenous nucleic acid sequences encoding phosphotransacetylase and/or phosphoketolase proteins, including a phosphoketolase protein from Clostridium acetobutylicum. Also disclosed are methods for generating recombinant yeast cells and methods of use of such cells for production of one or more products, including lipids, oils, fatty acids, and triacylglycerides.