טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMeizler Alon
SubjectEnzymatic Polymerization of Toxic Phenolic Compounds by
Immobilized Peroxidase in Continuous Regime
DepartmentDepartment of Agricultural Engineering
Supervisor Professor Emeritus Carlos Dosoretz


Abstract

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.