|M.Sc Student||Meizler Alon|
|Subject||Enzymatic Polymerization of Toxic Phenolic Compounds by|
Immobilized Peroxidase in Continuous Regime
|Department||Department of Agricultural Engineering||Supervisor||Professor Emeritus Carlos Dosoretz|
Phenols are oxidized by peroxidases and oxidases to generate phenoxyl radicals, which couple to form oligomeric and polymeric products. The increase in molecular weight results in a decrease in reactivity and solubility of the products, which tend to precipitate, a phenomenon which is apparently accompanied by a detoxification effect.
The overall objective of this research was to characterize the enzymatic polymerization reaction of 4-bromophenol (4-BP) as a model halogenated substrate, in continuous flow regime by immobilized horseradish peroxidase (HRP). Reactor performance and capacity were studied under various operating conditions. The enzyme was effectively (above 90% immobilization yield) covalently bound onto aminoalkylated controlled porous glass beads following modification of the enzyme with periodate.
Oxidation of 4-BP resulted in the formation of dimers up to at least pentamers as evidenced by mass spectrometry and size exclusion chromatography analysis. Although complete substrate transformation was achieved approx. 95% of the oxidized products, measured as total organic carbon (TOC), remained within the enzyme-glass matrix and 5% eluted from the reactor. The soluble carbon eluting the reactor appears as dimers and trimers.
Carbon mass-balance calculations made by elementary and TOC analyses following tetrahydrofuran extraction of the bed-matrix showed that 83% of material is adsorbed to the matrix whereas the remaining non-extractable 17% is perhaps bound. Concomitantly with the high degree of organic carbon removal achieved a relatively high degree of dehalogenation (40%) was achieved indicating a high degree of detoxification of the polymeric products formed.