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Date Permissions Signed


Date of Award

Winter 2021

Document Type

Masters Thesis

Department or Program Affiliation


Degree Name

Master of Science (MS)



First Advisor

Brodhagen, Marion (Marion L.)

Second Advisor

Peyron, Mark, 1961-

Third Advisor

Zinkgraf, Matthew


Although much work has been focused on micro and nano-plastics in soils, the bioactivity of common plastic additives (plasticizers) and monomers have been overlooked. One source of plastic pollution in agricultural soils is breakdown products from plastic soil covers called mulches. The plastics industry is attempting to make biodegradable plastic mulch (BPM) that have reduced environmental impacts and removal costs compared with those typically associated with conventional plastic mulches. Two common polymers added to BPMs are thermoplastic starch (TPS) and poly(butylene-adipate-co-terephthalate (PBAT). In this study, the effects of components that can leach from TPS and PBAT were investigated to determine their influence on growth and germination in four Aspergillus strains. Glycerol, a plasticizer that can leach from TPS, increased growth and germination for A. flavus. The PBAT breakdown product 1,4-butanediol did not alter germination in any of the four strains tested. The PBAT breakdown product adipic acid decreased germination in three strains, including A. flavus. The practical significance of these results is that within the microenvironment of BPMs, glycerol leaching from TPS could increase germination of a mycotoxin producing species of Aspergillus (A. flavus), increasing the potential for more toxins to enter the food system. Conversely, the release of organic acids from PBAT may cause acid stress to other microorganisms besides Aspergillus. Hydrolysis of ester linkages is a common mechanism for breakdown of most biodegradable polymers, so consideration of the effect of the resultant organic acids on microorganisms that colonize or break down these plastics is important.




plastic, biodegradable, adipic acid, glycerol, germination, Aspergillus


Western Washington University

OCLC Number


Subject – LCSH

Plastics--Biodegradation; Soil pollution--Environmental aspects; Polymers--Absorption and adsorption; Aspergillus--Effect of pollution on; Germination--Molecular aspects




masters theses




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