Microbial Fermentation Process for Ethanol Production
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Solution Overview
Problem
Current microbial fermentation processes for producing ethanol from carbon monoxide (CO) suffer from low efficiency due to co-production of acetate and the challenge of optimizing microbial growth and product conversion rates, leading to suboptimal ethanol production and potential greenhouse gas emissions from acetate conversion to methane.
Innovation Solution
A method is developed to improve microbial fermentation efficiency by adjusting the substrate supply rate based on the proportion of CO converted to CO2, ensuring optimal carbon fixation as desired products like ethanol or acetate, and transitioning microbial cultures through adjustments in pH, redox potential, and nutrient supply to maintain or shift product profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If microbial fermentation is used to convert CO to ethanol, then higher specificity and yields are achieved compared to catalytic processes, but the co-production of acetate reduces overall ethanol production efficiency
Solution Approach 1:
The patent applies parameter changes by adjusting pH and redox potential to control microbial metabolism. Specifically, maintaining pH between 5.0-7.0 and redox potential between -200mV to -400mV optimizes the microbial community to favor ethanol production over acetate formation, thereby improving ethanol production efficiency while reducing carbon loss to unwanted by-products
Solution Approach 2:
The patent implements feedback control by continuously monitoring the ratio of CO2 produced to CO consumed and using this information to adjust substrate supply rate. This feedback mechanism ensures optimal carbon fixation efficiency and maintains high ethanol production while minimizing acetate co-production, as the substrate supply is dynamically adjusted based on real-time metabolic activity measurements
2Productivity
If substrate supply rate is increased to improve ethanol production rate, then productivity increases, but carbon conversion efficiency may be compromised due to suboptimal microbial growth conditions
Solution Approach 1:
The patent uses feedback control where the substrate supply rate is dynamically adjusted based on the measured ratio of CO2 produced to CO consumed. This ensures that carbon conversion efficiency is maintained at optimal levels while maximizing ethanol production rate, as the system responds to real-time microbial metabolic state rather than operating at fixed substrate rates
Solution Approach 2:
The patent applies dynamics by making the substrate supply rate variable rather than constant. The supply rate is continuously adapted based on microbial growth phase and metabolic activity, allowing the system to optimize both productivity and carbon conversion efficiency at different stages of fermentation by matching substrate availability to microbial demand
3Reliability
If acetate is produced as a by-product during CO fermentation, then microbial growth is supported, but greenhouse gas emissions increase due to acetate conversion to methane
Solution Approach 1:
The patent applies parameter changes by controlling pH (5.0-7.0) and redox potential (-200mV to -400mV) to shift microbial metabolic pathways. These parameter optimizations suppress acetate formation and promote direct ethanol production from CO, thereby maintaining reliable microbial growth while minimizing greenhouse gas emissions from acetate-to-methane conversion
Solution Approach 2:
The patent converts the potential harm of acetate production into benefit by optimizing conditions to prevent acetate accumulation in the first place. By controlling pH and redox potential, the system directs carbon flow toward ethanol production rather than acetate formation, thus eliminating the harmful downstream effect of methane generation while maintaining microbial growth on the desired ethanol product
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 production rates, reduces acetate co-production, and maintains efficient carbon conversion, thereby improving the commercial viability and environmental sustainability of the fermentation process.
Implementation Method 1
microbial fermentation of a substrate comprising CO
Implementation Method 2
acetyl coenzyme A (acetyl CoA) biochemical pathway of autotrophic growth (also known as the Woods-Ljungdahl pathway and the carbon monoxide dehydrogenase/acetyl CoA synthase (CODH/ACS) pathway)
Implementation Method 3
Acetate produced as a by-product of the fermentation process described in WO 2007/117157 is converted into hydrogen gas and carbon dioxide gas
Data Source
AI summary
The invention relates to the production of products such as alcohols and acids by microbial fermentation, particularly microbial fermentation of substrates comprising CO. It more particularly relates to methods and systems for improving efficiency of products by microbial fermentation. In particular embodiments, the invention provides a method of optimizing production of desired products including the step of ascertaining the proportion of CO converted to CO2.