土壤中聚乙烯降解菌的筛选、鉴定及降解特性

Isolation of a polyethylene-degrading strain from farm soil

【目的】农用地膜主要成分为聚乙烯(polyethylene,PE),因其难以被降解,其废弃物常造成"白色污染",本研究从常年覆盖农用地膜的土壤中筛选PE降解菌,并探究其对PE制品的降解效能。【方法】采集的土壤样品用PE为唯一碳源的无机盐培养基进行富集,筛选、纯化PE降解菌,分离菌通过形态染色、生理生化特征、16S rRNA基因序列分析进行鉴定,检测其在不同PE浓度(0%、0.05%、0.10%、0.25%、0.50%、1.00%、2.00%、3.00%)的无机盐培养基中的生长曲线,最后通过扫描电镜、光镜观察,检测分离菌对农用地膜的降解效能。【结果】从土壤中筛选获得一株能够降解PE的分离菌株(命名为SW1),初步鉴定其为放线菌的诺卡氏菌属Nocardia sp.。SW1的生长对PE具有明显浓度依赖,在含2%PE的无机盐培养基中生长最快,在培养的第48 h菌液浓度开始明显增加,第60 h达到最大,而在不含PE的无机盐培养基中未见生长。形态生理学观察表明,35°C培养15d后,扫描电镜观察可见有大量菌嵌入膜内或附于膜表面生长,膜表面粗糙,并开始出现破损;培养60 d后,光镜观察可见膜大面积破损,并出现空洞。【结论】从土壤中筛选获得了一株能够有效降解PE制品的放线菌菌株Nocardia sp. SW1。该研究丰富了PE制品降解微生物的菌种资源,为PE塑料废弃物的生物降解提供了科学数据与参考。

[Objective] The main component of agricultural mulch film is polyethylene. Because it is difficult to be degraded, its waste often causes "white pollution". In this study, polyethylene degrading bacteria were screened from the soil covered with agricultural mulch all the year round, and the degradation efficiency of polyethylene products was also explored. [Methods] Polyethylene-degrading bacteria were enriched, screened and purified using the inorganic salt medium with polyethylene as the sole carbon source. The isolated bacteria were identified by colony, morphological staining, physiological and biochemical characteristics and 16 S rRNA gene phylogenetic analysis. The growth curves of isolated strain were detected under different concentrations(0, 0.05%, 0.10% 0.25%, 0.50%, 1%, 2% and 3%) of polyethylene. Finally, the biodegradation of the agricultural mulch film was detected using scanning electron microscopy and light microscopy. [Results] A strain(named as SW1) which could degrade polyethylene was isolated from soil and identified as of Nocardia sp. The growth of SW1 was dependent on the concentration of polyethylene. It grew fastest in the inorganic salt medium containing 2% polyethylene. At 48 h, the concentration of the bacterial solution began to increase;at 60 h, it reached the maximum. Meanwhile, no growth was found in the inorganic salt medium without polyethylene. In the inorganic salt medium containing agricultural mulch film, after culture at 35 °C for 15 d, a large number of bacteria were observed to be embedded in the film or attached to the surface of the film by scanning electron microscopy, the surface of the film was rough, and began to be damaged. After culture for 60 d, the membrane of the inoculated group was damaged in a large area and cavity appeared. [Conclusion] Nocardia sp. SW1 isolated from farm soil can degrade polyethylene products effectively. This study enriches the degradation microbial resources of polyethylene products, and provides scientific data and reference for the biodegradation of polyethylene plastic waste.