Phenols containing halogens, which tend to deactivate the aromatic nuclei, constitute a significant category of highly toxic and difficult-to-degrade pollutants, which arise from a wide variety of industries. The main purpose of this study was to obtain an inexpensive immobilized enzyme for the removal of phenols. Partially purified potato polyphenol oxidase (PPO) was immobilized onto different commercial and laboratory produced carriers. Three of the obtained biocatalysts, with the highest PPO activities, namely Eupergit C250L-PPO; Celite-PPO and Cellulose M-PPO, were tested in a batch reactor for the removal of phenol, 4-chlorophenol and 4-bromophenol. In the case of 2.5 mM substrates with Eupergit C250L-PPO, an around 45% removal of 4-bromophenol was achieved, while the removals 4-chlorophenol and phenol were 35% and 20%, respectively. The reusability of Eupergit C250L-PPO for the removal of 4-chlorophenol was tested. After eight repeated tests, the efficiency of 4-chlorophenol removal by Eupergit C250L-PPO immobilizate had decreased to 55%.

Yeast Saccharomyces cerevisiae is the most significant source of enzyme invertase. It is mainly used in the food industry as a soluble or immobilized enzyme. The greatest amount of invertase is located in the periplasmic space in yeast. In this work, it was isolated into two forms of enzyme from yeast S. cerevisiae cell, soluble and cell wall invertase (CWI). Both forms of enzyme showed same temperature optimum (60°C), similar pH optimum, and kinetic parameters. The significant difference between these biocatalysts was observed in their thermal stability, stability in urea and methanol solution. At 60°C, CWI had 1.7 times longer half-life than soluble enzyme, while at 70°C CWI showed 8.7 times longer half-life than soluble enzyme. After 2-hr of incubation in 8 M urea solution, soluble invertase and CWI retained 10 and 60% of its initial activity, respectively. During 22 hr of incubation of both enzymes in 30 and 40% methanol, soluble invertase was completely inactivated, while CWI changed its activity within the experimental error. Therefore, soluble invertase and CWI have not shown any substantial difference, but CWI showed better thermal stability and stability in some of the typical protein-denaturing agents.