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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Microbiol. | doi: 10.3389/fmicb.2019.02548

Bacillus pumilus B12 Degrades Polylactic Acid and Degradation is Affected by Changing Nutrient Conditions

  • 1The University of Tennessee, Knoxville, United States
  • 2Institute of Agriculture, University of Tennessee, Knoxville, United States
  • 3Columbus State University, United States
  • 4Microbiology, The University of Tennessee, Knoxville, United States

Poly-lactic acid (PLA) is increasingly used as a biodegradable alternative to traditional petroleum-based plastics. In this study, we identify a novel agricultural soil isolate of Bacillus pumilus (B12) that is capable of degrading high molecular weight PLA films. This degradation can be detected on a short timescale, with significant degradation detected within 48-hours by the release of L-lactate monomers, allowing for a rapid identification ideal for experimental variation. The validity of using L-lactate as a proxy for degradation of PLA films is corroborated by loss of rigidity and appearance of fractures in PLA films, as measured by atomic force microscopy and scanning electron microscopy, respectively. Furthermore, we have observed a dose-dependent decrease in PLA degradation in response to an amino acid/nucleotide supplement mix that is driven mainly by the nucleotide base adenine. In addition, amendments of the media with specific carbon sources increase the rate of PLA degradation, while phosphate and potassium additions decrease the rate of PLA degradation by B. pumilus B12. These results suggest B. pumilus B12 is adapting its enzymatic expression based on environmental conditions and that these conditions can be used to study the regulation of this process. Together, this work lays a foundation for studying the bacterial degradation of biodegradable plastics.

Keywords: Poly-lactic acid, Plastic degradation, Enzyme Assays, Bacillus, regulation

Received: 01 Jul 2019; Accepted: 22 Oct 2019.

Copyright: © 2019 Bonifer, Wen, Hasim, Phillips, Dunlap, Gann, DeBruyn and Reynolds. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Todd B. Reynolds, The University of Tennessee, Knoxville, Microbiology, Knoxville, 37996, Tennessee, United States, treynol6@utk.edu