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Synergistic Mutations Create Bacillus Subtilisin Variants with Enhanced Poly-l-Lactic Acid Depolymerization Activity
Jordan A Cannon1, Todd B Reynolds1
1Department of Microbiology, University of Tennessee at Knoxville, Knoxville, Tennessee 37996, United States.
Biomacromolecules
|February 13, 2023
Summary
Researchers identified a Bacillus pumilus subtilisin capable of enzymatic recycling of poly-l-lactic acid (PLLA) plastic. Engineering efforts yielded hyperactive variants, significantly enhancing PLLA depolymerization for improved plastic biodegradation.
Area of Science:
- Biotechnology
- Polymer Science
- Enzymology
Background:
- Enzymatic recycling of poly-l-lactic acid (PLLA) is gaining interest.
- Limited understanding of enzymatic mechanisms and engineering strategies hinders PLLA depolymerization efficiency.
Purpose of the Study:
- Identify and characterize subtilisins from Bacillus species for PLLA depolymerization.
- Investigate mutations to enhance enzyme activity for improved PLLA biodegradation.
- Understand the structural basis for enhanced enzymatic activity.
Main Methods:
- Comparative mutational analysis of subtilisins from Bacillus pumilus and Bacillus subtilis.
- In silico modeling to predict changes in enzyme structure and function.
- Generation and testing of hyperactive enzyme variants for PLLA depolymerization.
Main Results:
- A subtilisin from Bacillus pumilus was identified with high-molecular-weight PLLA depolymerization capability.
- Mutational analysis revealed key residues enhancing enzyme activity.
- Engineered variants showed significant increases in activity (830-fold for B. subtilis, 184-fold for B. pumilus).
- In silico modeling indicated improved binding pocket accessibility and surface hydrophobicity.
Conclusions:
- Subtilisins from Bacillus species are effective biocatalysts for PLLA depolymerization.
- Enzyme engineering strategies can significantly enhance PLLA degradation.
- Hyperactive variants demonstrate potential for practical applications in PLLA plastic recycling.
