Screening and Characterization of Polyethylene-Degrading Bacteria from Mangrove Sediments
[Objective]To explore the degradation characteristics of Polyethylene(PE)plastics by microorganisms in mangrove sediments in Mazhang District of Zhanjiang City,and to enrich mangrove plastic degradation bacteria.[Method]Nine samples were randomly selected from the high,middle,and low tide zones of mangroves in Mazhang District of Zhanjiang City,and a 5-point sampling method was used to sample the sediments from 2-5 cm deep soil layers of mangroves.The collected sediment samples were enriched,separated,and purified in the inorganic salt medium with polyethylene as the only carbon source to screen out strains capable of degrading PE,and their species were determined by means of microscopic morphological analysis and molecular identification.The degradation performance of the microplastics was verified by measuring the growth curve,weight loss rate,and analysis of functional group changes.[Result and Conclusion]Three strains of PE-degrading bacteria,K1-1,K1-2 and K1-3,were selected from the sediments.They were Acinetobacter venetianus,Pseudomonas juntendi,and Bacillus wiedmannii.The growth curve of these strains was parabolic during the 120 d culture cycle.After the action of the three strains,a hydroxyl group was formed on the surface of PE,and amino and hydroxyl compounds were formed.The hydroxyl group replaces the carbonyl group,resulting in obvious changes in the apparent and internal structures of PE.After 120 days of treatment,the weight losses of PE were 6.42%,5.38%and 5.73%,respectively.The weight loss rate of strain K1-1 increased by 3.55%compared with that of strain Bacillus gottheilii,which had the highest degradation efficiency in mangrove sediments.This discovery confirmed the potential of A.venetianus for the degradation of PE plastics,enriched the species of PE-degrading bacteria in mangrove sediments in Zhanjiang,and provided technical support for the biodegradation of PE plastics.
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