State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Sci Total Environ. 2021 Feb 20;756:144087. doi: 10.1016/j.scitotenv.2020.144087. Epub 2020 Nov 26.
Polypropylene (PP), a fossil-based polyolefin plastics widely used worldwide, is non-hydrolyzable and resistant to biodegradation as a major source of plastic pollutants in environment. This study focused on feasibility of PP biodegradation in the larvae of two species of darkling beetles (Coleoptera: Tenebrionidae) i.e., yellow mealworms (Tenebrio molitor) and superworms (Zophobas atratus) using PP foam with number-, weight-, and size-average molecular weights (M, M, and M) of 109.8, 356.2, and 765.0 kDa, respectively. The tests were conducted in duplicates with respective larvae (300 T. molitor and 200 Z. atratus each incubator) at 25 °C and 65% humidity for over a 35-day period. The larvae of T. molitor and Z. atratus fed with PP foam as sole diet consumed PP at 1.0 ± 0.4 and 3.1 ± 0.4 mg 100 larvae days, respectively; when fed the PP foam plus wheat bran, the consumption rates were enhanced by 68.11% and 39.70%, respectively. Gel permeation chromatography analyses of the frass of T. molitor and Z. atratus larvae fed PP only indicated that M was decreased by 20.4 ± 0.8% and 9.0 ± 0.4%; M was increased by 12.1 ± 0.4% and 61.5 ± 2.5%; M was decreased by 33.8 ± 1.5% and 32.0 ± 1.1%, indicating limited extent depolymerization. Oxidation and biodegradation of PP was confirmed through analysis of the residual PP in frass. Depression of gut microbes with the antibiotic gentamicin inhibited PP depolymerization in both T. molitor and Z. atratus larvae. High throughput 16S rRNA sequencing revealed that Citrobacter sp. and Enterobacter sp. were associated with PP diets in the gut microbiome of Z. atratus larvae while Kluyvera was predominant in the T. molitor larvae. The results indicated that PP can be biodegraded in both T. molitor and Z. atratus larvae via gut microbe-dependent depolymerization with diversified microbiomes.
聚丙烯（PP）是一种广泛应用于全球的基于化石的聚烯烃塑料，作为环境中主要的塑料污染物来源，它不可水解且抗生物降解。本研究聚焦于两种暗黑鳃金龟幼虫（鞘翅目：鳃金龟科），即黄粉虫（Tenebrio molitor）和超级粉虫（Zophobas atratus），对 PP 泡沫塑料的生物降解可行性，所用 PP 泡沫塑料的数均分子量（M）、重均分子量（M）和分子量分布（M）分别为 109.8、356.2 和 765.0 kDa。试验在 25℃和 65%湿度条件下，各设置 300 只黄粉虫和 200 只超级粉虫的 2 个重复实验组进行，为期 35 天。以 PP 泡沫塑料为唯一食物的黄粉虫和超级粉虫幼虫，分别消耗 1.0±0.4 和 3.1±0.4 mg 100 幼虫天；当添加麦麸时，消耗率分别提高了 68.11%和 39.70%。仅喂食 PP 泡沫塑料的黄粉虫和超级粉虫幼虫粪便的凝胶渗透色谱分析表明，M 降低了 20.4±0.8%和 9.0±0.4%；M 增加了 12.1±0.4%和 61.5±2.5%；M 降低了 33.8±1.5%和 32.0±1.1%，表明解聚程度有限。通过分析粪便中残留的 PP，证实了 PP 的氧化和生物降解。抗生素庆大霉素抑制黄粉虫和超级粉虫幼虫的肠道微生物，从而抑制 PP 解聚。高通量 16S rRNA 测序显示，在超级粉虫幼虫肠道微生物组中，与 PP 饮食相关的微生物为柠檬酸杆菌属（Citrobacter sp.）和肠杆菌属（Enterobacter sp.），而优势菌为克吕沃尔氏菌属（Kluyvera）。结果表明，PP 可通过肠道微生物依赖的解聚作用在黄粉虫和超级粉虫幼虫中生物降解，其肠道微生物组多样化。
