Electrochemical synthesis and characterization of a polipyrrole/lipase composite film

Abstract

The advantages of an irreversible immobilized enzyme for heterogeneous catalytic transformations of different substrates are numerous. In particular, since the enzyme macromolecules remains attached to the inert support it may be possible to re-use it. In some cases the immobilized molecules are more stable than the species of the solution. The kinetics of the immobilized species is likely to be influenced by the microenvironment and may be considerably altered from solution kinetics. Slow mass transfer of immobilized enzymes make possible advantageous treatment of substrate dilute solutions (waste waters etc). One of immobilization technique is entrapment in polymer matrices which cover a variety of different polymerization methods and polymer characteristics. The polymer may be an inert support (polystyrene, polyacrylamide etc) or may perform some functions itself. Conducting polymer in particular electrochemically deposited polymershave became of interest as support matrices for enzymes. Polypyrrol (Ppy) films are known to be permeable and appear to offer an ideal matrix for enzymes immobilization. Electro polymerization of pyrrole from an aqueous solution containing an enzyme (glucose oxydase) produced a Polypyrrol film containing the enzyme. The electro polymerization via a radical cation, which reacts with neighbouring pyrrolle to produce a chain that is α, α’ coupled. The resulting polymer incorporates anions of supporting electrolyte and has a net positive charge. Some authorsi,ii,iii have reported that the polypyrrole are degraded at same potential values This finding emphases that slight modifications in polymerization can alter the characteristics of the resultant polymer. Immobilization efficiency depends strongly on the composition and the structure of the entrapping polymer and this depends on the degree of cross linking and concentration of the monomer. So, it is important to manipulate the electropolymerization of pyrrole which would give a film that must be sufficiently porous to assure a maximum entrapping efficiency. The aim of this work is the study of immobilization efficiency in polypyrrole film of an acylhidrolaze (lipase) of molecular mass of 33-65 KDa obtained from Yarrowia lipolitica yeast.