Two-Vessel PHB Bioreactor for Direct Depolymerization and Repolymerization
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Solution Overview
Problem
Current methods are inadequate for efficiently recycling and repolymerizing hydroxybutyrate (HB) into polyhydroxybutyrate (PHB) due to the lack of thermally and thermodynamically stable enzymes that can function in contaminated environments, such as those found in post-consumer products, and existing processes fail to bypass acetyl-CoA-dependent pathways.
Innovation Solution
A two-vessel bioreactor system utilizing extremophilic microorganisms and enzymes, including hydroxybutyrate dehydrogenase (HBD) and acetoacetyl-CoA synthetase (ACS), to convert HB into PHB through a non-naturally occurring pathway that bypasses acetyl-CoA, allowing for efficient recycling and repolymerization in a closed system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional enzymatic pathways are used to convert hydroxybutyrate to polyhydroxybutyrate, then the process can proceed through natural metabolic routes, but the enzymes lack thermal and thermodynamic stability in contaminated environments and require acetyl-CoA-dependent pathways
Solution Approach 1:
The patent employs extremophilic microorganisms that have adapted to extreme environmental conditions (high temperature, high salinity, pH extremes). These organisms produce enzymes with altered physical and chemical parameters that confer thermal stability and resistance to contamination. The enzymes from extremophiles maintain catalytic activity under conditions where conventional enzymes would denature or lose function, thereby resolving the reliability issue without requiring complex process controls.
Solution Approach 2:
The patent extracts and utilizes a specific enzymatic pathway from extremophilic microorganisms that bypasses the acetyl-CoA-dependent conventional pathway. By isolating and implementing this alternative pathway using extremophilic enzymes, the system eliminates the complexity associated with acetyl-CoA metabolism while achieving the same conversion goal. The extracted enzymatic route is more direct and suitable for contaminated environments.
2Ease of manufacture
If hydroxybutyrate is depolymerized and stored before repolymerization, then the monomers can be processed separately, but this increases process time and risk of contamination
Solution Approach 1:
The patent combines the depolymerization and repolymerization operations into a single integrated bioreactor system. Extremophilic microorganisms are introduced that can simultaneously perform both functions: breaking down polyhydroxybutyrate into hydroxybutyrate monomers and immediately repolymerizing them back into polyhydroxybutyrate. This eliminates the need for separate storage and handling steps, reducing process time and contamination risk while maintaining operational flexibility.
Solution Approach 2:
The patent implements a continuous cycle where depolymerization and repolymerization occur simultaneously and continuously within the bioreactor. The extremophilic enzymes operate in a continuous manner, converting monomers to polymer and back without interruption or intermediate storage. This continuous action eliminates idle time associated with batch processing and storage, maximizing productivity while minimizing exposure to contamination risks.
3Productivity
If conventional biodegradation pathways are used, then hydroxybutyrate can be broken down for energy, but the process cannot repolymerize the monomers back into polyhydroxybutyrate
Solution Approach 1:
The patent implements a circular process where polyhydroxybutyrate is depolymerized into hydroxybutyrate monomers, which are then immediately repolymerized back into polyhydroxybutyrate. The extremophilic enzymes facilitate this cycle, allowing the system to recover and reuse the polymer material rather than allowing it to be permanently degraded for energy alone. This approach recovers the valuable polymer substance while still allowing energy production during the intermediate depolymerized state.
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
The system achieves high yield and purity in recycling PHB from post-consumer products, reducing contamination risks and operational costs by simultaneously degrading and repolymerizing HB into PHB, suitable for reuse in consumer products.
Implementation Method 1
contacting a post-consumer product with an extremophilic microorganism suspension or an extremophilic depolymerase enzyme to supply a hydroxyalkanoate monomer
Implementation Method 2
converting the hydroxybutyrate monomer to acetoacetate with a hydroxybutyrate dehydrogenase enzyme
Implementation Method 3
converting acetoacetate to acetoacetyl-CoA with an Acetoacetyl-CoA synthetase enzyme
Implementation Method 4
reducing acetocetyl-CoA to hydroxybutyrl-CoA with an acetoacetyl-CoA reductase
Implementation Method 5
polymerizing hydroxybutyryl-CoA with a hydroxybutyrate polymerase to form polyhydroxybutyrate
Data Source
AI summary
A bioreactor and process are disclosed for forming polyhydroxybutyrate directly from depolymerized polyhydroxybutyrate. In two bioreactor vessels, a microorganism product, such as one or more enzymes, are combined with the polyhydroxybutyrate-containing post-consumer product materials. The microorganism can naturally secrete the one or more enzymes or can be genetically modified to secrete the enzyme. The combination of enzymes is designed to facilitate a metabolic pathway that can depolymerize PHB, convert the resulting hydroxybutyrate to hydroxybutyryl-CoA, and in turn polymerize it into PHB. Namely, a solution for the recycling of polyhydroxybutyrate to hydroxybutyrate and back to polyhydroxybutyrate.