Plastic pollution in the environment is a critical problem in the word. There are so many factors that have a momentous effect on the degradation of the plastics. Among all the factors, the enzymes involved in plastic degradation is the main factor that can be released from the different microorganisms and degraded the plastics.
Enzymes can not directly involve in the degradation, it is used for the degradation after building culture supernatants or partially purification. Some enzyme is mentioned in following which has a vital effect on the biodegradation of petroleum-based plastics.
10 Enzymes involved in Plastic Degradation:
Laccases are present in the lignin-biodegrading fungi and can help in the oxidation of the hydrocarbon backbone of polyethylene. UV-irradiated PE film in both culture supernatants and cell-free extracts can be degraded by laccase from Rhodococcus ruber C208, Bacillus cereus in the presence of copper and also the molecular weight of a PE membrane can be reduced strongly by laccase from Trametes versicolor in the presence of 1-hydroxy benzotriazole.
Manganese peroxidase (MnP):
Manganese peroxidase release from Bacillus cereus for degradation of UV-irradiated and from Phanerochaete chrysosporium ME-446, Penicillium simplicissimum for the loss of the high molecular weight of PE.The genes which are encoding in the most MnP from IZU-154 and liable for the degradation of nylon-66.
Streptomyces contains LiP for the degradation of the PE fraction of a heat-treated plastic blend.
A preoxidized high molecular weight PE can be degraded by the extracellular LiP and MnP of Phanerochaete chrysosporium MTCC-787.
Papain and urease:
The proteolytic enzymes as papain and urease from Trichoderma sp. Are found to degrade medical polyester polyurethane.
Lipase from Rhizopus delemar has been explored for the degradation of low molecular weight PLA and high molecular weight can be degraded with the strains of Amycalotopsis sp.
Alkane hydroxylases (AH):
Low molecular weight PE (20%) can be converted into CO2 by a recombinant AH from Pseudomonas sp. E4 expressed in Escherichia coli BL21.
An alkane monooxygenase, rubredoxin and rubredoxin reductase from Pseudomonas aeruginosa E7 degraded about 30% of the PE.
A membrane-bound esterase of Delftia acidovorans is used for the degradation of Polyurethane(PUR).
Carboxylesterases from Bacillus licheniformis, Bacillus subtilis and Thermobifida fusca and show high activity against PET oligomers.
Polyurethane esterase from Comamonas acidovorans has been considered for the degradation of low molecular weight PLA.
Pseudomonas spp. are and C. acidovorans break down the ES-PU consist of poly (diethylene adipate) contained a type of esterase.
Protease is produced by Brevibacillus spp., Bacillus spp., which are responsible for the capable of biodegradation of plastics.
Serine hydrolases from Pestalotiopsis microspore utilize the polyurethane as a substrate, source of carbon and
degrade it. Depolymerases are serine hydrolases that can attack the branching chains and the cyclic components of the polymers.
Putative polyurethanases from Pseudomonas chlororaphis
and Comomonas acidovorans as well as the fungus Candida rugosa are responsible for the polymer degradation.
Cutinases & Polyester Hydrolases :
At 70ºC temperature, A thermostable cutinase HiC from Thermomyces (formerly Humicola) hydrolyzed a low crystalline (7%) PET film and degrade the crystalline part of the PET film at this reaction temperature. The thermostable bacterial LC-cutinase hydrolyzed approximately 25% of a low crystalline PET film at the same reaction temperature.
Polyester hydrolases of Thermobifida species are homologous to the encoding gene of this enzyme. polyester hydrolase TfCut2 from Thermobifida fusca KW3 degrade amorphous PET films at 70°C in the absence of metal ions.
Microbial enzymes induce the rate of biodegradation of plastics very effectively without causing any harm to the environment. The enzymatic biodegradation of plastic that will enhance the biodegradation rate.