A first look at some potentially plastic degrading enzymes

Sammanfattning: The many advantageous abilities of plastics have made them omnipresent in today’s society. However, the low cost of production, light weight, durability and insolubility in water combined with inadequate waste handling have led to a vast and increasing accumulation of plastics in nature, approximated to be over 6 300 million tons (Geyer, Jambeck and Law, 2017, ‘Production, use, and fate of all plastics ever made’, Science Advances, 3(7), pp. 1-5). In addition to being unsustainable and environmentally hazardous, this is an enormous waste of resources. Thus, new recycling methods which are economically favourable compared to de novo production and which don’t require any hazardous chemicals or large amounts of energy are being sought among organisms which are able to degrade what was previously considered biologically non-degradable plastics. One such organism is the bacteria Ideonella sakaiensis which is able to use PET (for instance used in soda bottles) as its source of carbon and energy using a PET-degrading enzyme known as PETase (Yoshida et al., 2016, ‘A bacterium that degrades and assimilates poly(ethylene terephthalate)’, Science, 351(6278, pp. 1196-1199). In this thesis, the first glance at a number of novel PETase-homologs as well as a lipase is presented, including the results of their expression, melting point and hydrolysis of para-nitrophenyl esters. Nothing conclusive can be stated regarding the plastic degrading abilities (or lack thereof) of the proteins, but the results may provide some insights beneficial to future studies.