Plastic products made of polyethylene (PE), polypropylene (PP), and polystyrene (PS) are widely used in daily life and industrial production. Polyolefins-which have a very stable structure and do not contain any active molecular groups-are difficult to degrade and pose a serious global environment threat. This study selected latex clearing protein (LcpK30) derived from Streptomyces sp. Strain K30. The natural substrate of the enzyme is rubber (cis-1, 4-polyisoprene), and the site of action is the carbon‑carbon double bond. LcpK30 was incubated with UV-irradiated polyolefin PE, PP and PS (UV-PE, UV-PP, and UV-PS containing carbon‑carbon double bonds) for 5 d at 37 °C. The results showed that UV-PE-LcpK30 was more fragmented than UV-PE-blank; the Fourier transform infrared spectroscopy results showed that UV-PE-LcpK30 and UV-PP-LcpK30 produced new active groups (e.g., -OH and -C=O); however, the effect on UV-PS was not significant. Scanning electron microscopy results showed that the treated group had more obvious roughness, cracks, and pits than the control group. The results of high-temperature gel permeation chromatography showed that the average molecular weight (Mw) of UV-PE-LcpK30 and UV-PP-LcpK30 decreased; the Mw of UV-PE5-LcpK30 was reduced by 42.02%. The results of gas chromatography-mass spectrometry showed the production of ketones. Therefore, the LcpK30 latex clearing protein degrade UV-oxidized polyolefin plastics and has great potential for PE and PP degradation but may not be suitable for PS. Furthermore, other Lcps (such as LcpNRRL, LcpNVL3) can also degrade UV-PE.
Keywords: Biodegradation; Lcp(K30); Plastic waste; Polyolefin.
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