Surface-associated residues in subtilisins contribute to poly-L-lactic acid depolymerization via enzyme adsorption
Jordan A Cannon1, Yue Zhou1, Luke T Qualey1
1Department of Microbiology, University of Tennessee at Knoxville, Knoxville, Tennessee, USA.
Microbial Biotechnology
|June 15, 2024
Summary
Enzymatic recycling of poly-L-lactic acid (PLLA) is enhanced by engineering subtilisin enzymes. Surface amino acids and increased hydrophobicity improve PLLA depolymerization by promoting enzyme adsorption to the polymer.
Area of Science:
- Biotechnology
- Polymer Science
- Enzymology
Background:
- Poly-L-lactic acid (PLLA) is a prevalent bioplastic with limited biodegradability and recycling options.
- Enzymatic recycling offers a circular economy approach for PLLA, necessitating improved enzyme activity and mechanistic understanding.
Purpose of the Study:
- To engineer PLLA-depolymerizing subtilisin enzymes from Bacillus species.
- To elucidate molecular mechanisms governing PLLA depolymerization activity.
- To enhance enzyme function through protein engineering.
Main Methods:
- Comparative analysis of surface-associated amino acids in Bacillus subtilis (BsAprE) and Bacillus pumilus (BpAprE) subtilisins.
- Engineering of BsAprE with identified surface-associated amino acids from BpAprE.
- In silico protein modeling to assess enzyme surface hydrophobicity and structural motifs.
- Experimental validation of enhanced PLLA depolymerization activity.
Main Results:
- Identified specific surface-associated amino acids in BpAprE that enhance PLLA depolymerization when engineered into BsAprE.
- In silico modeling revealed increased surface hydrophobicity and a favored structural motif in active BsAprE variants.
- Experimental data indicated that enhanced activity correlates with improved polymer binding (adsorption) rather than substrate specificity.
Conclusions:
- Enzyme adsorption is a critical factor for efficient PLLA depolymerization by subtilisins.
- Protein engineering strategies targeting surface properties can significantly enhance enzyme performance for bioplastic recycling.
- Understanding enzyme-polymer interactions is key to developing effective enzymatic recycling processes for PLLA.
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