Biodegradation of Polyethylene by a Soil Bacterium and AlkB Cloned Recombinant Cell

A mesophilic bacterium capable of Low-Molecular-Weight Polyethylene (LMWPE) biodegradation was isolated from a beach soil having been contaminated extensively with crude oil. The isolated strain was rod-shaped gram negative bacterium and was identified as Pseudomonas sp. E4 through the 16S rDNA sequencing. The biodegradability test in the compost inoculated with the isolated strain for LMWPE having weight-average-molecularweight (Mw) in the range of 1,700~23,700 indicated that 4.9~28.6 % of the carbon was mineralized into CO2 after 80 days at 37°C. The biodegradability decreased with increase in Mw of LMWPE. In comparison to other previous works which reported biodegradation of pre-oxidized polyethylene, we investigated biodegradation of non-oxidized LMWPE whose Mw was well above the Mw upper limit penetrable through microbial membrane. The smooth surface of LMWPE sheet became eroded as a result of the biodegradation, and the degree of the surface erosion became more pronounced for LMWPE with lower molecular weight in line with the biodegradability test results. The alkane hydroxylase gene (alkB) of Pseudomonas sp. E4 was expressed in Escherichia coli BL21 and the recombinant E. coli BL21 mineralized 19.3% of the carbon of LMWPE into CO2 during the biodegradation in the compost at 37°C for 80 days, while the recipient cell was not active at all toward the LMWPE biodegradation, indicating that the alkB from Pseudomonas sp. E4 plays a central role in the LMWPE degradation even in the absence of the other specific enzymes like rubredoxin and rubredoxin reductase.