Microbial Consortium Fermentation for High-Yield Low-Emission Butanol
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Solution Overview
Problem
Conventional methods for producing butanol rely on petrochemical routes that are environmentally deleterious and result in low yields with greenhouse gas emissions, while microbial fermentation pathways suffer from inefficiencies and byproduct release.
Innovation Solution
A microbial consortium involving lactic acid bacteria (LAB), acetogens, and solventogenic Clostridia is used to convert carbohydrates into butanol, with a two-step fermentation process that includes electrochemical reduction of CO2 to formate, which is then utilized to enhance acetate and butanol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If microbial fermentation pathways are used to produce butanol from renewable feedstocks, then environmental sustainability is improved, but production yields remain low and greenhouse gas emissions occur
Solution Approach 1:
The fermentation process is divided into two distinct stages with different microbial communities: Stage 1 uses LAB and acetogens to convert carbohydrates to acetate with high carbon efficiency, while Stage 2 uses solventogenic Clostridia to convert acetate to butanol. This segmentation allows each stage to be optimized independently, achieving both high sustainability in Stage 1 and high butanol yield in Stage 2.
Solution Approach 2:
Acetate serves as an intermediary metabolite between the first fermentation stage (carbohydrate to acetate) and the second fermentation stage (acetate to butanol). This intermediary allows the decoupling of carbon-efficient acetate production from butanol synthesis, enabling the system to achieve both high sustainability and high productivity that neither single-stage fermentation can achieve alone.
2Productivity
If conventional petrochemical routes are used to produce butanol, then high product yields are achieved, but environmentally deleterious chemicals are used
Solution Approach 1:
The invention changes the fundamental parameters of the production system by replacing petrochemical feedstocks with renewable carbohydrates and replacing chemical catalysis with biological fermentation pathways. The two-stage fermentation process achieves petrochemical-level yields (0.56 g/g) while using only renewable resources and benign biological processes, fundamentally altering the environmental profile of butanol production.
3Device complexity
If single-stage fermentation is used to convert carbohydrates to butanol, then process simplicity is maintained, but carbon efficiency is low and greenhouse gas emissions occur
Solution Approach 1:
The fermentation process is divided into two distinct stages with different microbial communities: Stage 1 uses LAB and acetogens to convert carbohydrates to acetate with high carbon efficiency, while Stage 2 uses solventogenic Clostridia to convert acetate to butanol. This segmentation allows each stage to be optimized independently, achieving both high sustainability in Stage 1 and high butanol yield in Stage 2.
Solution Approach 2:
The system implements metabolic feedback by using the acetate produced in Stage 1 as the primary substrate for Stage 2, creating a coupled system where the output of the first stage directly fuels the second stage. This feedback loop maximizes carbon utilization by directing carbon flow from carbohydrates through acetate to butanol, minimizing losses to greenhouse gases.
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 achieves high butanol yields of up to 0.56 g/g from glucose with reduced greenhouse gas emissions, utilizing renewable feedstocks and improving carbon efficiency through optimized microbial interactions.
Implementation Method 1
a lactic acid bacterium (LAB) and an acetogen, thereby forming a first fermentation mixture; incubating the first fermentation mixture under conditions effective to produce acetate from carbohydrate, lactate and formate
Implementation Method 2
produce acetate from carbohydrate, lactate and formate
Implementation Method 3
contacting a second portion of the carbohydrate-containing source with acetate and a second inoculant comprising a solventogenic Clostridia, thereby forming a second fermentation mixture; and incubating the second fermentation mixture under conditions effective to produce the carbonaceous product (e.g., butanol)
Implementation Method 4
electrochemical reduction of CO2 to formate, which is then utilized to enhance acetate and butanol production
Data Source
AI summary
Described herein are methods to convert a carbohydrate-containing source to a carbonaceous product. In some aspects, the methods include contacting a first portion of the carbohydrate-containing source with a first inoculant comprising a LAB and acetogen, thereby forming a first fermentation mixture; incubating the first fermentation mixture to produce acetate; contacting a second portion of the carbohydrate-containing source with acetate and a second inoculant comprising a solventogenic Clostridia, thereby forming a second fermentation mixture which is incubated to produce the carbonaceous product. Also disclosed herein are fermentation inoculants for the conversion of a carbohydrate-containing source to a carbonaceous product, the inoculant comprising a LAB expressing an enzyme catalyzing the production of lactate from the source, a mixotrophic acetogen expressing an enzyme that catalyzes the production of acetate from lactate and formate, and a solventogenic Clostridia expressing an enzyme that catalyzes the production of the carbonaceous product from the carbohydrate source.