EAGER: Biodegradable mulch films in agriculture as a potential source of contaminated plastic pollution

1665408 Brodhagen大型塑料薄膜（地膜）在农业中用于覆盖土壤以保持水分并抑制杂草生长。塑料和农业工业的一个目标是设计可生物降解的塑料地膜，这种地膜可以被耕作到土壤中，在土壤中降解是几年的时间。可生物降解的塑料被设计成在微生物的帮助下分解成二氧化碳、水和甲烷。然而，该过程固有地需要在矿化的途中形成从宏观到分子水平的塑料碎片。该项目的目标是评估这些塑料碎片在土壤生态系统中的影响，这在很大程度上是未知的。PI旨在：1）使用与农业覆盖物中使用的聚合物相关的聚合物生产和表征纯聚合物膜，描述其降解产物，并优化测量和量化土壤和水介质中降解产物的方法。2)在一项原理验证研究中使用黄曲霉毒素，这是农业土壤中发现的一种常见的、具有重要经济意义的天然毒素，以探讨天然毒素是否有可能吸附和积累在土壤中的生物降解塑料碎片上。产生黄曲霉毒素的真菌，黄曲霉，是淀粉基生物可降解塑料的频繁和狂热的定殖者，和，3）询问真菌是否被淀粉聚合物或生物可降解塑料聚合物或两者吸引。PI将评估A的整体基因表达。黄曲霉毒素在可生物降解塑料上生长时会产生毒性，因为除了黄曲霉毒素外，黄曲霉毒素还会产生其他次级代谢产物，对土壤食物网具有潜在毒性。原位分析聚合物降解的能力将允许对土壤生态系统中可生物降解塑料地膜的命运进行逼真的建模。本研究将代表文献报道的在现实条件下真实的土壤中商业相关聚合物降解特性的最彻底比较。了解黄曲霉和黄曲霉毒素与可生物降解聚合物的相互作用将有助于产生用于农业和食品包装的可生物降解塑料配方，这些配方不太可能被黄曲霉毒素污染。评估黄曲霉在生物可降解聚合物上生长期间表达的基因将揭示黄曲霉产生的许多水解酶是否参与聚合物分解以及哪些参与聚合物分解。此外，次级代谢物基因表达的改变将支持进一步的实验，以评估黄曲霉毒素和其他微生物代谢物吸附到可生物降解的塑料地膜碎片上的潜力-从其自然作用中分离出来，并集中在可能进入食物网的颗粒上。自2011年秋季以来，10名WWU生物和7名WWU工程本科生在生物降解塑料项目上获得了1-2年的研究经验。其中，五名学生是同行评审出版物的合著者。所有这些学生都在他们感兴趣的领域，研究生课程或医学院进行研究工作。两名接受该补助金培训的本科研究人员将有优势全职专注于他们的项目，因为他们将获得津贴。他们将接受跨学科研究方法的培训，参加联合实验室会议，并在大学级会议（学者周）上展示他们的数据。这项工作的结果将与农业生态系统和人类健康有关。原位分析聚合物降解的能力将允许对土壤生态系统中可生物降解塑料地膜的命运进行现实建模，并为研究土壤中聚合物降解产物的命运和运输铺平道路。

1665408BrodhagenLarge plastic sheets (mulch films) are used in agriculture to cover the soil to retain moisture and inhibit weed growth. A goal of the plastics and agricultural industries is the design of biodegradable plastic mulch films that can be tilled into the soil, where degradation is on the order of years. Biodegradable plastics are designed to disintegrate, with the help of microorganisms, into carbon dioxide, water, and methane. However, the process inherently requires plastic fragments ranging from macroscopic to molecular level to be formed en route to mineralization. The goal of this project is the assessment of effects of these plastic fragments in soil ecosystems which is largely unknown.The PIs aims to: 1) produce and characterize pure polymer films using polymers relevant to those used in agricultural mulches, describe their degradation products, and optimize methods for measuring and quantifying degradation products in soil and aqueous media. 2) use aflatoxin, a common and economically important natural toxin found in agricultural soils, in a proof-of-principle study to ask whether natural toxins have potential to adsorb and accumulate on fragments of biodegradable plastics in soil. The fungus that produces aflatoxin, Aspergillus flavus, is a frequent and avid colonizer of starch-based biodegradable plastics, and, 3) query whether the fungus is attracted to the starch polymers or the biodegradable plastic polymers, or both. The PIs will assess global gene expression of A. flavus during growth on biodegradable plastics because, besides aflatoxin, it produces other secondary metabolites that are potentially toxic in the soil food web. The ability to analyze in situ polymer degradation will allow realistic modeling of the fate of biodegradable plastic mulch films in soil ecosystems. This study would represent the most thorough comparison of the degradation characteristics of commercially-relevant polymers in real soil under realistic conditions yet reported the literature. Understanding the interaction of Aspergillus flavus and aflatoxin with biodegradable polymers will aid in generating biodegradable plastic formulations used in agriculture and food packaging that are less likely to become contaminated with aflatoxin. Assessing genes expressed by Aspergillus flavus during growth on biodegradable polymers will reveal whether, and which of, the many hydrolytic enzymes produced by Aspergillus flavus are involved in polymer breakdown. In addition, altered expression of secondary metabolite genes would support further experiments to assess the potential for aflatoxin and other microbial metabolites to adsorb to biodegradable plastic mulch film fragments - sequestered from their natural roles, and concentrated onto particles that may enter the food web. Since the fall of 2011, ten WWU Biology and seven WWU Engineering undergraduate students have gained 1-2 years' research experience on the biodegradable plastics project. Of those, five students were coauthors on peer-reviewed publications. All of these students have gone on to research jobs in their field of interest, graduate programs, or medical school. Two undergraduate researchers trained on this grant would have the advantage to focus full-time on their projects because they will be paid stipends. They will receive training in interdisciplinary research methods, attend joint laboratory meetings, and present their data at a university-level conference (Scholars Week). The results from this work will be relevant to agroecosystem and human health. The ability to analyze in situ polymer degradation will allow realistic modeling of the fate of biodegradable plastic mulch films in soil ecosystems and pave the way for studies of fate and transport of polymer degradation products in soils.