Screening of polyethylene film-degrading bacteria from gut microbiota of Galleria mellonella and Tenebrio molitor

Abstract:

[Background] Polyethylene mulch film is widely used for agricultural production in China. Because it is very difficult to be naturally degraded in the fields, it finally accumulates in the soil and negatively affects the growth of crops and the ecological environment. Therefore, it is of great significance to explore the microbial resources for biodegradation of such “white pollution”. [Objective] Bacteria were isolated and screened from the intestinal flora of plastic-eating insects such as Galleria mellonella and Tenebrio Molitor from different sources, and their degradation efficiency of agricultural plastic film was characterized. [Methods] The larvae of Galleria mellonella and Tenebrio molitor were domesticated by polyethylene membrane, and the bacteria with polyethylene as the sole carbon source were isolated from intestinal bacteria by collecting intestinal fluid, enriching culture, co-metabolic domestication and selecting culture medium. The strain was inoculated into the medium with polyethylene membrane as the only carbon source for co-culture. The degradation effect of the strain on polyethylene mulch film was evaluated by measuring cell growth, regularly detecting the weight loss rate of the film, combined with high-resolution field emission scanning electron microscope observation, infrared scanning analysis and determination of mechanical properties of the film. The strains with good degradability were identified by 16S rRNA gene amplification and sequence analysis. [Results] Most polyethylene-degrading bacteria were isolated from the intestines of the indigenous Galleria mellonella in the honeybee hive in Xinjiang, and the degradation efficiency of polyethylene was higher than that of the isolates from other sources. Three strains XJDLM-3, XJDLM-8 and XJDLM-12, with high degradation ability were selected to grow using polyethylene membrane. scanning electron microscope observation showed that obvious erosion holes and cracks appeared on the surface of degraded polyethylene film after 30 days, and the infrared scanning pattern changed. The mechanical properties such as tensile strength, elongation at break and elastic modulus decreased significantly, and the weight loss rate of polyethylene diaphragm reached 8.06%, 5.66% and 5.39%, respectively. A bacterial strain with good degradation effect was isolated from the intestines of the native Galleria mellonella in the honeybee hive in Xinjiang. XJDLM-8 and XJDLM-12 were identified as Bacillus cereus, XJDLM-3 and Enterobacter bugandensis. [Conclusion] Strains were isolated with high ability to degrade polyethylene in the intestines of the native Galleria mellonella in the honeybee hive in Xinjiang, to provide the potential of development and application in the degradation of polyethylene mulch film.