Sulfur Additives for Ethanol Fermentation from Carbon Monoxide

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Solution Overview

Problem

Current methods for producing ethanol and acetate from carbon monoxide and carbon dioxide using anaerobic fermentation face challenges in providing a cost-effective and bioavailable form of sulfur, as hydrogen sulfide is toxic and volatile, limiting the efficiency and cost-effectiveness of the process.

Innovation Solution

The use of sulfur additives such as sulfurous acid, bisulfite, metabisulfite, and thiosulfate provides bioavailable sulfur oxyanions that meet the metabolic needs of carboxydotrophic microorganisms, reducing the need for cysteine and minimizing hydrogen sulfide volatility, thereby enhancing the production of ethanol and acetate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hydrogen sulfide is used as a sulfur source for anaerobic fermentation, then the sulfur needs of microorganisms are met, but the process suffers from toxicity and volatility issues that reduce efficiency and increase costs

Engineering Contradiction:

Improvemicroorganism growth supportVSAvoidtoxicity and volatility of hydrogen sulfide

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary substance (sulfate or sulfite salt) that serves as a safe carrier form of sulfur. This intermediary is non-toxic and non-volatile, yet can be converted by the microorganisms into the required hydrogen sulfide form internally, thus mediating between the safe external storage form and the required internal metabolic form.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the oxidation state parameter of sulfur from -2 (in hydrogen sulfide) to +6 (in sulfate) or +4 (in sulfite). This parameter change transforms the harmful, volatile hydrogen sulfide into a stable, non-toxic salt form that can be safely handled and stored, while still being metabolically convertible to the required form.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If cysteine is used as a sulfur source, then microorganism metabolic needs are satisfied, but the operational costs increase due to higher material requirements

Engineering Contradiction:

Improvemetabolic sulfur supplyVSAvoidoperational cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive organic sulfur sources (cysteine) with inexpensive inorganic sulfur salts (sulfate or sulfite). These cheap inorganic salts serve as disposable sulfur sources that the microorganisms can efficiently utilize, significantly reducing material costs while maintaining metabolic functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Productivity

If traditional sulfur sources are used, then fermentation can proceed, but contaminant growth is not effectively inhibited reducing product purity

Engineering Contradiction:

Improvefermentation rateVSAvoidcontaminant growth

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent utilizes the pH-dependent speciation parameter of sulfur compounds. At the acidic fermentation pH (4.0-5.0), the sulfate/sulfite exists primarily as protonated forms (HSO4- or HSO3-) that can inhibit contaminants while remaining metabolically convertible by the desired microorganisms. This parameter-based differentiation allows selective inhibition.

Inventive Principle:

Principle #35Parameter changes

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 allows for higher ethanol production rates and lower operational costs by maintaining a stable and bioavailable sulfur supply, inhibiting contaminant growth, and improving the alcohol to acid product ratio, with ethanol to acetate ratios exceeding 5:1.

Implementation Method 1

Method for producing C2 oxygenates by fermentation using high oxidation state sulfur - producing ethanol and/or acetate from substrates of carbon monoxide and/or carbon dioxide and hydrogen by anaerobic fermentation using carboxydotrophic microorganisms

Methodology Applied

Scientific EffectFermentation: Fermentation

Implementation Method 2

using specific sources of inorganic sulfur to supply the biological sulfur needs of the microorganisms - sulfur additives such as sulfurous acid, bisulfite, metabisulfite, and thiosulfate provides bioavailable sulfur oxyanions

Methodology Applied

Scientific EffectReduction: Reduction

Data Source

PatentUS9212375B2Method for producing C2 oxygenates by fermentation using high oxidation state sulfur

Publication Date: 2015.12.15 SYNATA BIO INC

AI summary

The invention relates to improvements in the production of ethanol and acetate by microbial fermentation, particularly to production of alcohols by microbial fermentation of a substrate comprising CO and the addition of an inorganic sulfur additive. It more particularly relates to the provision of an inorganic organic sulfur source to a fermentation system such that one or more microorganisms convert a substrate comprising CO to ethanol. In one aspect the invention uses a sulfur additive comprising inorganic sulfur compounds having a +2 to a +4 sulfur oxidation state that produces sulfur oxoanions and hydrosulfur oxoanions in an aqueous fermentation medium.