Alpha-Amylase Variants With Higher Fermentation Solubility
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Solution Overview
Problem
The existing α-amylase from Bacillus sp. no. 707 is not expressed at high levels, making its economical manufacture and commercial use challenging, despite its superior performance compared to other variants like Bacillus sp. A 7-7 α-amylase.
Innovation Solution
Modifying the amino acid sequence of the Bacillus sp. no. 707 α-amylase to increase its solubility in fermentation broths, allowing for higher expression levels and more efficient recovery, by introducing specific amino acid variations that promote solubility and reduce hydrophobic residues on the enzyme surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Bacillus sp. no. 707 α-amylase is used for its superior performance, then the enzyme performance is improved, but the expression level is low making economical manufacture difficult
Solution Approach 1:
The patent applies parameter changes by modifying amino acid residues in the α-amylase sequence to alter its solubility properties. Specific substitutions (e.g., hydrophobic to hydrophilic residues) change the physical-chemical parameters of the enzyme, enabling higher expression levels while preserving catalytic performance.
Solution Approach 2:
The patent applies local quality by making targeted modifications at specific locations (amino acid positions) rather than uniform changes throughout the sequence. This allows localized improvement of solubility at the protein surface while maintaining the functional integrity of the catalytic domain.
2Reliability
If the Bacillus sp. no. 707 α-amylase is used for its superior performance, then the enzyme activity is improved, but the solubility in fermentation broth is low leading to aggregation and precipitation
Solution Approach 1:
The patent changes the solubility parameter by substituting amino acid residues that affect protein-solvent interactions. Hydrophobic residues on the surface are replaced with hydrophilic ones, fundamentally changing the enzyme's solubility characteristics without compromising its catalytic activity.
Solution Approach 2:
The patent converts the harmful effect of hydrophobic surface residues (which cause aggregation) into a benefit by strategically replacing them. The same positions that originally caused precipitation are transformed into regions that promote solubility, turning a detrimental property into an advantageous one.
3Productivity
If amino acid modifications are introduced to increase solubility, then the expression level and recovery efficiency are improved, but the enzyme sequence diverges from the wild-type
Solution Approach 1:
The patent maintains sequence fidelity by limiting modifications to specific local regions (surface-exposed amino acid positions) rather than throughout the entire sequence. This localized approach preserves the overall sequence identity and structural integrity while achieving the desired solubility improvement.
Solution Approach 2:
The patent carefully controls the extent of parameter changes by selecting specific amino acid substitutions rather than extensive modifications. This controlled change strategy achieves sufficient solubility enhancement while maintaining sequence fidelity and avoiding over-engineering.
Data Source
AI summary
Variants of Bacillus sp. no. 707 alpha amylase are provided that are produced more efficiently and thus more economically. Higher fermentation yields are achieved through introducing amino acid variations that promote solubility of the variant in a fermentation broth. Increased solubility allows more enzyme to remain in solution after expression in a host cell. This in turn increases the efficiency with which the expressed variant enzyme can be recovered from the fermentation broth.