Genetically Modified Yeast for Acetic Acid Conversion

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Solution Overview

Problem

Current methods for producing ethanol from lignocellulosic biomass face challenges due to the inhibitory effects of acetic acid and the formation of glycerol as a by-product, which reduces ethanol yield and requires additional steps to manage redox balance in yeast fermentation.

Innovation Solution

Genetically modified yeast cells are developed to include nucleotide sequences encoding NAD+-dependent acetylating acetaldehyde dehydrogenase, acetyl-CoA synthetase, glycerol dehydrogenase, and dihydroxyacetone kinase, along with the deletion of glycerol 3-phosphate dehydrogenase genes, enabling the conversion of acetic acid and glycerol into ethanol while avoiding intracellular glycerol production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If glycerol production is reduced to increase ethanol yield, then ethanol yield is improved, but redox balance issues worsen

Engineering Contradiction:

Improveethanol yieldVSAvoidredox balance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent converts the harmful accumulation of NADH (which causes redox imbalance) into a beneficial outcome by introducing an acetic acid conversion pathway. The NADH is consumed in the reduction of acetyl-CoA to ethanol via the introduced enzymes (acetaldehyde dehydrogenase and alcohol dehydrogenase), thereby resolving the redox balance issue while simultaneously converting acetic acid (a toxic by-product) into useful ethanol.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Quantity of substance

If acetic acid is present in hydrolysates, then substrate availability is improved, but fermentative capacity is inhibited

Engineering Contradiction:

Improvesubstrate availabilityVSAvoidfermentative capacity inhibition

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent transforms acetic acid, which is toxic to yeast at high concentrations, into a valuable substrate for ethanol production. By introducing the acetic acid conversion pathway (acetyl-CoA synthetase, acetaldehyde dehydrogenase, and alcohol dehydrogenase), the system consumes acetic acid and converts it to ethanol, thereby eliminating its toxic effect while increasing ethanol yield.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the metabolic parameters of the yeast by introducing heterologous genes and modifying enzyme activities. This enables the yeast to utilize acetic acid as a carbon source and convert it to ethanol, fundamentally altering the fermentation process to tolerate and benefit from high acetic acid concentrations that would normally inhibit fermentation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If glycerol is produced as a by-product, then redox balance is maintained, but ethanol yield is reduced

Engineering Contradiction:

Improveredox balanceVSAvoidethanol yield

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent eliminates the need for glycerol production as a redox balancing mechanism by providing an alternative NADH consumption pathway through acetic acid conversion. The introduced enzymes (acetaldehyde dehydrogenase and alcohol dehydrogenase) consume NADH during acetic acid to ethanol conversion, thereby maintaining redox balance while directing carbon flux toward ethanol production instead of glycerol by-product formation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach enhances ethanol yield by eliminating glycerol production and increasing the conversion of acetic acid, thereby improving the efficiency of ethanol production from lignocellulosic hydrolysates under anaerobic conditions.

Implementation Method 1

nucleotide sequence encoding a heterologous NAD+-dependent acetylating acetaldehyde dehydrogenase

Methodology Applied

Scientific EffectEnzyme catalysis: Enzyme

Implementation Method 2

nucleotide sequence encoding a homologous or heterologous acetyl-CoA synthetase

Methodology Applied

Scientific EffectEnzyme catalysis: Enzyme

Implementation Method 3

nucleotide sequence encoding a heterologous glycerol dehydrogenase

Methodology Applied

Scientific EffectEnzyme catalysis: Enzyme

Implementation Method 4

nucleotide sequence encoding a homologous or heterologous dihydroxyacetone kinase

Methodology Applied

Scientific EffectEnzyme catalysis: Enzyme

Implementation Method 5

yeast cells produce fermentation product such as ethanol

Methodology Applied

Scientific EffectFermentation: Fermentation

Data Source

PatentUS11753659B2Glycerol and acetic acid converting yeast cells with improved acetic acid conversion

Publication Date: 2023.09.12 DANISCO US INC

AI summary

Cell that is genetically modified comprising:a) one or more nucleotide sequence encoding a NAD+-dependent acetylating acetaldehyde dehydrogenase (E.C. 1.2.1.10);b) one or more nucleotide sequence encoding a acetyl-CoA synthetase (E.C. 6.2.1.1);c) one or more nucleotide sequence encoding a glycerol dehydrogenase (E.C. 1.1.1.6); andd) one or more nucleotide sequence encoding a dihydroxyacetone kinase (E.C. 2.7.1.28 or E.C. 2.7.1.29).