Topographical imaging as a means of monitoring biodegradation of poly(hydroxyalkanoate) films |
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Authors: | Richard D Ashby Peter Cooke Daniel K Y Solaiman |
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Institution: | (1) Fats, Oils and Animal Coproducts Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA |
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Abstract: | Poly(hydroxyalkanoates) (PHAs) are a class of bacterially-derived polymers that are naturally biodegradable through the action
of extracellular depolymerase enzymes secreted by a number of different bacteria and fungi. In this paper we describe the
development of topographical imaging protocols (by both scanning electron microscopy; SEM, and confocal microscopy; CM) as
a means of monitoring the biodegradation of solution cast films of poly(3-hydroxybutanoate-co-3-hydroxyhexanoate) (P3HB/3HHx) and medium-chain-length (mcl-) PHA. Pseudomonas lemoignei and Comamonas P37C were used as sources for PHA depolymerase enzymes as these bacteria are known to degrade at least one of the polymers
in question. SEM revealed the bacterial colonization of the film surfaces while CM permitted the comparative assessment of
the roughness of the film surfaces upon exposure to the two bacterial strains. By dividing the total surface area of the film
(A′) by the total area of the scan (A) it was possible to monitor biodegradation by observing differences in the topography
of the film surface. Prior to inoculation, P3HB/3HHx films had an A′/A ratio of 1.06. A 24-h incubation with P. lemoignei increased the A′/A ratio to 1.47 while a 48- and 120-h incubation with Comamonas resulted in A′/A ratios of 1.16 and 1.33, respectively. These increases in the A′/A ratios over time demonstrated an increase
in the irregularity of the film surface, indicative of PHA polymer breakdown.
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and does not imply recommendation or endorsement by the U.S. Department of Agriculture. |
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Keywords: | Poly(3-hydroxybutanoate-co-3-hydroxyhexanoate) Degradation Scanning electron microscopy Confocal microscopy Topography |
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