Extractive Fermentation for Butanol Production
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Solution Overview
Problem
Current methods for producing butanol through microbial fermentation are limited by butanol toxicity to the host microorganism, leading to reduced yields and titer, and existing chemical synthetic methods are expensive and environmentally unfriendly.
Innovation Solution
A method involving a genetically modified microorganism that produces butanol from a fermentable carbon source, with the use of a water immiscible organic extractant to extract butanol into a separate phase during fermentation, allowing for increased titer and yield by reducing toxicity exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If butanol is produced by fermentation using Clostridium acetobutylicum or recombinant microbial hosts, then butanol can be produced as a renewable biofuel alternative to petrochemical methods, but butanol toxicity limits the effective titer and yield to below 12 g/L
Solution Approach 1:
The patent applies in situ extractive fermentation where an organic solvent (such as n-butyl alcohol, n-amyl alcohol, or their esters) is introduced into the fermentation medium to continuously extract butanol from the aqueous phase. This removes the toxic butanol product from the vicinity of the microorganism, allowing higher production rates and final titers without being limited by toxicity thresholds.
Solution Approach 2:
The organic solvent acts as an intermediary phase between the aqueous fermentation medium and the butanol product. It facilitates the transfer of butanol from the aqueous phase where it is produced to an organic phase where it is stored, thereby protecting the microorganism from direct exposure to high concentrations of toxic butanol while enabling continuous product accumulation.
2Productivity
If chemical synthetic methods are used to produce butanol, then high production rates can be achieved, but the process is expensive and environmentally unfriendly due to reliance on petrochemicals
Solution Approach 1:
The patent employs genetically modified microbial hosts with altered metabolic pathways that redirect carbon flux toward butanol production. By modifying enzyme expression levels, pathway regulation, and cofactor availability, the system achieves high butanol titers through fermentation rather than chemical synthesis, maintaining productivity while improving environmental sustainability and reducing dependence on petrochemical feedstocks.
3Quantity of substance
If recombinant microbial hosts expressing butanol biosynthetic pathways are used, then higher yields can be achieved compared to native Clostridium acetobutylicum, but butanol toxicity still limits the effective titer
Solution Approach 1:
The patent combines recombinant microbial hosts with in situ extractive fermentation, where an organic solvent continuously removes butanol from the aqueous fermentation medium. This extraction system prevents butanol accumulation to toxic levels, allowing the recombinant host to maintain high production rates and achieve effective titers significantly exceeding the 12 g/L limitation of conventional fermentation.
Solution Approach 2:
The system creates a composite fermentation environment combining the aqueous phase (containing microorganisms and nutrients) with an organic phase (containing the extractant solvent). This two-phase system allows simultaneous microbial growth and product extraction, enabling the recombinant host to produce butanol at high yields without being constrained by toxicity thresholds.
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 method enhances butanol production by maintaining the butanol concentration below toxic levels for the microorganism, resulting in higher effective titer and yield, and produces a biofuel that is environmentally friendly and can be blended with fossil fuels.
Implementation Method 1
contacting the fermentation medium with i) at least one first water immiscible organic extractant selected from the group consisting of C12 to C22 fatty alcohols, C12 to C22 fatty acids, esters of C12 to C22 fatty acids, C12 to C22 fatty aldehydes, C12 to C22 fatty amides and mixtures thereof
Data Source
AI summary
A method of making butanol from at least one fermentable carbon source that overcomes the issues of toxicity resulting in an increase in the effective titer, the effective rate, and the effective yield of butanol production by fermentation utilizing a recombinant microbial host wherein the butanol is extracted into specific organic extractants during fermentation.