Water-Soluble Polymer Capsules for Low-Shear Microorganism Encapsulation
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Solution Overview
Problem
Existing encapsulation methods for sensitive microorganisms, such as those sensitive to high shear forces, high temperatures, or reactive chemicals, result in low viability and limited control over capsule size, making it challenging to maintain the integrity and stability of these organisms during encapsulation.
Innovation Solution
The use of polymer capsules with water solubility above 1 g/l and an average particle size below 100 μm, formed through an all-aqueous emulsion process using polymers like dextran, starch, and alginate, which are crosslinked to enhance stability and control capsule size, allowing for low-shear encapsulation of microorganisms like Bacillus species and other microbes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional encapsulation methods (spray-drying, fluidized bed drying, electrospraying) are used, then capsules can be formed, but the high temperatures, shear forces, or reactive chemicals involved result in low viability of sensitive microorganisms
Solution Approach 1:
The patent changes the physical and chemical parameters of the encapsulation process by using all-aqueous systems at low temperatures (4-25°C) with controlled pH (5-8) and ionic strength (0.1-0.5 M), replacing conventional high-temperature spray-drying and chemical cross-linking methods. This parameter transformation preserves microorganism viability while achieving stable capsule formation through reversible polymer phase separation
Solution Approach 2:
The patent creates an inert aqueous environment using buffered salt solutions (e.g., phosphate-buffered saline, citrate buffers) that provide a chemically benign atmosphere during encapsulation. This inert aqueous medium protects sensitive microorganisms from harmful chemical interactions while enabling controlled polymer phase separation and capsule formation
2Manufacturing precision
If conventional encapsulation methods are used, then capsules can be formed, but control over capsule size is limited and particle size distribution is broad
Solution Approach 1:
The patent achieves precise capsule size control (d90 < 100 μm) by transforming the phase separation mechanism from conventional methods to a controlled all-aqueous two-phase system. By adjusting polymer concentrations, molecular weights, and solution conditions, the patent enables tunable capsule sizes without complex device modifications, achieving narrow size distributions through thermodynamic control rather than mechanical constraints
Solution Approach 2:
The patent employs dynamic control of polymer phase separation by adjusting environmental parameters (temperature, pH, ionic strength) during the encapsulation process. This dynamic approach allows real-time control of capsule nucleation and growth, enabling precise size control while maintaining process simplicity and avoiding fixed geometric constraints
3Ease of manufacture
If water-soluble polymers are used for encapsulation, then the capsules can be formed in all-aqueous systems, but the capsules may lack sufficient stability and integrity during storage and application
Solution Approach 1:
The patent creates composite capsule structures by combining water-soluble polymers (e.g., dextran, starch, alginate, gelatin) with cross-linking agents (e.g., divalent cations, aldehydes, enzymes, genipin). This composite approach maintains the ease of all-aqueous manufacturing while introducing cross-linked networks that provide enhanced structural stability and integrity during storage and application
Solution Approach 2:
The patent applies preliminary cross-linking treatment to water-soluble polymer capsules to pre-establish structural stability before storage or application. By performing cross-linking as a preliminary step (using mild agents like divalent cations for alginate or transglutaminase for gelatin), the patent ensures capsules maintain their integrity throughout subsequent handling while preserving the benefits of all-aqueous formation
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 preserves the viability of sensitive microorganisms with high numbers of colony-forming units (CFU) and provides stable, small-sized capsules that maintain integrity during storage and application, suitable for crop protection and plant growth promotion.
Implementation Method 1
polymer P1 and polymer P2 form an aqueous two-phase system
Implementation Method 2
which are crosslinked to enhance stability and control capsule size
Data Source
AI summary
Polymer capsule comprising at least one polymer P1 and at least one microorganism M, wherein said polymer P1 has a solubility in water at 21° C. of at least 1 g/l and wherein said polymer capsule has an average particle size d90 of below 100 μm, wherein said microorganism M is distributed throughout said capsule.