Polyethylene (PE) is the most consumed plastic polymer in the world with
an annual consumption rate exceeding 25 million tons per year.
Due to its high durability polyethylene accumulates in the environment at an alarming rate. The drastic accumulation of polyethylene brought attention to the need for developing microbial methods that will efficiently biodegrade plastics.
This study focused on induction and optimization of the activity of bacterial laccase enzyme produced by several polyethylene degrading bacteria. Characterization of the growth of two of the bacterial strains (designated 712 and 707) revealed that they are thermophilic (optimal growth temperature of 45°C and 40°C, respectively) and neutrophils. Further evidence showed that both strains produce extra-cellular laccase enzymes that exhibited an optimal activity at 80ºC. Several organic molecules (xylan, ABTS [2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] and copper) were evaluated as inducers for laccase production. Optimal treatments for laccase induction were also examined by PE biodegradation processes.
All laccase activity assays included the use of 2,6-DiMethoxyPhenol (DMP) as an indicator for laccase activity and were measured at 490nm. The induction analyses were conducted at 330nm wavelength in which maximal absorbance is received by the type III copper in laccase's catalytic site.
This study explored new ways to improve plastic biodegradation and found that biodegradation activity attributed to bacterial laccase may be enhanced in the presence of xylan and/or Cu2+. Further research is required in order to establish an efficient method for biodegradation of polyethylene.
