A marine fungus Alternaria alternata FB1 efficiently degrades polyethylene

Huge quantities of plastic wastes have been accumulating in the environment causing serious ecological problems and significantly impacting the global carbon cycling. Plastic pollutions have been recognized as the most common and durable marine contaminants. Consequently, the marine environment is becoming a hot spot to screen microorganisms possessing potential plastic degradation capabilities. Here, by screening hundreds of plastic waste-associated samples, we isolated a fungus (named Alternaria alternata FB1) that possessing a prominent capability of colonizing on the polyethylene (PE) film. Through Scanning Electron Microscope (SEM) observation, we found this fungus could efficiently degrade the PE film and formed numerous obvious holes in the plastic surface. Moreover, the Fourier Transform Infrared (FTIR) imaging detected absorption peak in the vicinity of 1715 cm^-1, indicating the formation of carbonyl bonds (-CO-). Through X-Ray Diffraction (XRD) analysis, we found that the PE film treated by strain FB1 for 28 days showed an evident reduced relative crystallinity degree, resulting in a decrease from 62.79% to 52.02%. Strikingly, the molecular weight of PE film decreased 95% after 120 days treatment by strain FB1. Using GC-MS, we further clarified that a four-carbon product (named Diglycolamine) accounted for 93.28% of all degradation products. We defined 153 enzymes that potentially involved in the degradation of PE through a transcriptomic method. The degradation capabilities of two representative enzymes including a laccase (with a molecular weight about 59.49 kDa) and a peroxidase (with a molecular weight about 36.7 kDa) were verified. Lastly, a complete biodegradation process of PE was proposed. Given the extreme paucity of microorganisms and enzymes for effective degradation of PE in the present time, our study provides a compelling candidate for further investigation of degradation mechanisms and development of biodegradation products of PE.