Polypropylene and polyethylene were coated with alpha-Chymotrypsin
(a-CT) or subtilisin Carlsberg (SubC) or Burkholderia
cepacia lipase (lipase BC) by different immobilization procedures,
such as physical adsorption and covalent linking. This
latter procedure was based on the chemical functionalization
of the plastic surface by oxygen gas plasma treatment. Immobilization
of the enzyme was carried out by using as cross-linking
agent i) glutaraldehyde (GA) or ii) N’-diisopropylcarbodiimide
(DIC) and N-hydroxysuccinimide (NHS). The effects of duration
of the plasma treatment and the type of the immobilization
procedure on the transesterification activity of the enzyme
were investigated. In general polypropylene resulted a better
support than polyethylene. Moreover, a-CT showed higher
transesterification activity when immobilized with GA, while for
SubC, DIC and NHS were better cross-linking agents than GA.
No activity was observed with these enzymes when immobilization
was carried out by physical adsorption. On the contrary,
lipase BC immobilized by physical adsorption was even more
active than the free enzyme. Concerning thermal stability, immobilized
SubC was less stable than the free enzyme. Overall,
these results show that plastics endowed with biocatalytic
properties could be obtained by simple immobilization protocols
and that optimal immobilization conditions depend on the
type of starting plastic, plasma treatment, cross-linking method,
and the nature of the enzyme
