Modified Proteases for Accelerated PLLA Degradation

The Problem

Poly-L-lactic acid (PLLA) is a promising candidate to replace petroleum-based plastics. While PLLA is 100% biodegradable under tightly controlled composting conditions, the plastic cannot be recycled due to incomplete recovery of L-lactate monomers in these conditions. PLLA recycling via enzymatic depolymerization is an alternative that could recover the L-lactate and circularize PLLA use; however naturally occurring PLLA depolymerizing enzymes lend to low catalytic efficiencies against non-naturally occurring PLLA polymers, thus requiring engineered variants with increased activity.

The Solution

Researchers at the University of Tennessee have developed novel enzyme mutations with improved depolymerization of high molecular weight PLLA. Amino acid substitutions made to naturally occurring B. pumilus and K. aridium enzymes has led to increased surface area and hydrophobicity of the active site, amplifying the depolymerization activity of the base material.

Further modification of these novel mutants has also led to higher thermostability, thereby allowing these enzymes to maintain function under various working conditions. Further development will result in more efficient depolymerization of PLLA materials for recycling and remediation purposes used in industrial spaces.

Benefits

Benefit
~180X increase in depolymerization activity against PLLA with combinations of mutations.
Enzyme variants al show higher activity in depolymerizing PLLA than Proteinase K.
Method will lead to iterative subtilisin modifications with increased depolymerization efficiency.
Enzymes maintain depolymerization activity at 60-65C, with higher working temperatures as an active target for R&D.

More Information

Derek Eitzmann, Ph.D.
Assistant Technology Manager, Multi Campus Office
865-974-1882 | deitzman@tennessee.edu

UTRF Reference ID: 23021
Patent Status:

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Innovators

Jordan Cannon

PhD Candidate, Microbiology

Jordan Cannon is a graduate student in the Department of Microbiology at UT Knoxville. His research interests include identifying and characterizing enzymes involved in PLLA depolymerization as well as engineering them for increased specificity for PLLA. The ultimate goal for this work is to utilize engineered variants in enzymatic recycling processes for PLLA.

Dr. Todd Reynolds

Associate Professor, Microbiology

Dr. Reynolds received his PhD from Vanderbilt University in 1999. His research interests include fungal pathogenesis and plastic degradation. Dr. Reynolds leads the Reynolds lab, which aims to understand the mechanisms by which soil microbes regulate degradation processes.

Modified Proteases for Accelerated PLLA Degradation​