Rhodococcus rhodochrous Strain for Acrylic Acid Production
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Solution Overview
Problem
Current methods for producing acrylic acid, such as chemical catalysis and direct fermentation, face issues with selectivity, impurities, energy-intensive purification, and toxicity to microorganisms, while biocatalytic processes using nitrilases are limited by substrate concentration and intermediate product contamination.
Innovation Solution
A genetically modified strain of Rhodococcus rhodochrous with deactivated nitrile hydratase genes and induced nitrilase activity, capable of converting acrylonitrile to acrylic acid using a single metabolic pathway, is developed, utilizing isobutyronitrile inhibition and ε-caprolactam induction to optimize enzyme activity at high acrylonitrile concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chemical catalysis is used to produce acrylic acid from propylene, then production scale is achieved, but selectivity deteriorates and impurities are formed
Solution Approach 1:
The patent replaces chemical catalysis with biological catalysis (enzymatic conversion). Specifically, it uses the enzyme nitrilase to convert acrylonitrile to acrylic acid, substituting the chemical catalyst system with a biological enzyme system that provides both high productivity and high selectivity without the impurity formation associated with chemical catalysis
Solution Approach 2:
The patent changes the operating parameters from high-temperature chemical catalysis to mild biochemical conditions. The enzymatic process operates at lower temperatures and neutral pH, transforming the reaction conditions to achieve both high productivity and selectivity simultaneously
2Productivity
If chemical catalysis is used to produce acrylic acid, then production rate is achieved, but energy consumption for purification increases
Solution Approach 1:
The patent substitutes chemical catalysis with enzymatic catalysis, where the enzyme nitrilase specifically converts acrylonitrile to acrylic acid with high selectivity. This biological system eliminates the need for energy-intensive distillation purification steps required by chemical catalysis, achieving both high production rate and low energy consumption
3Ease of manufacture
If direct fermentation of glucose is used to produce acrylic acid, then biocatalysis is achieved, but product titer deteriorates due to toxicity
Solution Approach 1:
The patent uses acrylonitrile as an intermediary substrate that is converted to acrylic acid by the enzyme nitrilase. This approach avoids direct fermentation of glucose to acrylic acid, instead using acrylonitrile as the starting material that can be converted to high titers of acrylic acid without the toxicity issues that limit glucose-based pathways
4Productivity
If nitrile hydratase is used to convert acrylonitrile to acrylic acid, then conversion is achieved, but intermediate contamination increases
Solution Approach 1:
The patent extracts and eliminates the unwanted intermediate acrylamide by using a nitrilase enzyme that directly converts acrylonitrile to acrylic acid in a single step, bypassing the two-step pathway through nitrile hydratase that produces acrylamide as an intermediate. This extraction of the problematic intermediate pathway achieves both conversion and purity
5Productivity
If nitrilase is used at high acrylonitrile concentrations, then substrate utilization is improved, but enzyme inhibition increases
Solution Approach 1:
The patent optimizes the operational parameters of the nitrilase enzyme, specifically adjusting pH to neutral conditions and controlling temperature, to maintain enzyme activity at high acrylonitrile concentrations. These parameter changes allow the enzyme to function reliably across a wide substrate concentration range without inhibition
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 energy efficiency by reducing intermediate products and enzymes, achieving high-yield, pure acrylic acid production without unwanted by-products, even at elevated acrylonitrile concentrations.
Implementation Method 1
Use is made of a genetically engineered strain of Escherichia coli to produce 3-hydroxypropionic acid and then acrylic acid from glucose fermentation. The fermentation of glucose to 3-hydroxypropionic acid is followed by three enzymatic steps to produce an acrylic acid and CoA combination from which acrylic acid can be extracted.
Implementation Method 2
A biosynthetic pathway which employs a nitrilase to convert acrylonitrile to acrylic acid and ammonium acrylate. Nitrilases are enzymes available in mostly soil-inhabiting microorganisms like Rhodococcus rhodochrous.
Implementation Method 3
The second pathway relies on the microorganism's production of nitrile hydratase and amidase to produced acrylic acid in a two-step process in which the acrylonitrile is converted to acrylamide (unwanted intermediate) by nitrile hydratase and the subsequently the acrylamide is converted to acrylic acid by amidase.
Implementation Method 4
the acrylonitrile is converted to acrylamide (unwanted intermediate) by nitrile hydratase and the subsequently the acrylamide is converted to acrylic acid by amidase
Implementation Method 5
A first fermentation process makes use of a renewable carbon source and produces lactic acid, 3-hydroxypropionic acid and glycerol. The process is carried out using naturally occurring microorganisms.
Data Source
AI summary
A strain of Rhodococcus rhodochrous in which a gene coding at least part of a nitrile hydratase enzyme or any gene coding a protein involved in the transcription, translation or formation of at least part of the nitrile hydratase enzyme has been deactivated or rendered ineffective or a strain of Rhodococcus rhodochrous cultured under condition wherein the nitrile hydratase enzyme is been inhibited.