Some kinetic properties of polyphenol oxidase from Thymbra spicata L. var. spicata

Immobilization, optimization, characterization and kinetic properties of polyphenol oxidase to multi-walled carbon nanotube

In this study, the kinetic properties of polyphenol oxidase (PPO) extracted from Satureja cuneifolia were investigated using catechol and 4-methylcatechol as substrates. Optimal pH and temperature values were determined at each purification step. Subsequently, the optimum immobilization conditions were established as 2 hours of stirring time and 0.05 g of multi-walled carbon nanotubes (MWCNTs). Characterization by BET, FTIR, DTA/TG, TEM, and SEM/EDX analyses confirmed the successful immobilization of PPO onto mesoporous MWCNTs, with notable changes in surface morphology and thermal degradation behavior. The optimum pH for the free enzyme remained constant across purification methods but varied with the substrate, while the optimum temperature was consistently found at 30 °C. Upon immobilization, the optimum temperature shifted to higher values, indicating enhanced thermal stability. Catalytic efficiency (Vmax/KM) for catechol decreased significantly after immobilization (from 2.5 × 106 to 5 × 104 min-1), whereas for 4-methylcatechol, the immobilized enzyme retained a high catalytic efficiency (Vmax/KM =1 × 106 min-1), comparable to that of the free enzyme. This shift suggests that immobilization favored substrate specificity toward 4-methylcatechol. Overall, the MWCNT-PPO system demonstrated enhanced stability, improved reusability, and altered substrate selectivity, making it a strong candidate for industrial biocatalytic applications where operational durability and efficiency are critical.

Intrinsic polyphenol oxidase-like activity of gold@platinum nanoparticles

Au@Pt NPs showed PPO mimetic activity over a wider range of pH and temperatures compared to PPO. In the oxidation of all substrates, Au@Pt NPs exhibited higher affinity to the substrates, especially to catechol and pyrogallol, compared with PPO.

Ellagic acid from acorn fringe by enzymatic hydrolysis and combined effects of operational variables and enzymes on yield of the production

The individual effects of three different enzyme types -- one single enzyme (ellagitannin acyl hydrolase) and two combinations of enzymes (ellagitannin acyl hydrolase-beta-glucosidase-polyphenol oxidase and ellagitannin acyl hydrolase-cellulase-xylanase) -- on ellagic acid yield, combined with other process parameters -- enzyme concentration, hydrolysis time, particle size and solid-to-liquid ratio -- were evaluated by response surface methodology. The selection of the enzymes for the study was based on preliminary experiments that showed higher increments in ellagic acid yield. The quantitative parameters studied were enzyme concentration (0.1, 0.45, 2 w/w or %), solid-to-liquid ratio (0.05, 0.15, 0.2), particle size (220, 445, 900 microm) and hydrolysis time (60, 89, 132 min). Experimental data for ellagic acid yield obtained with a single enzyme and two combination enzymes correlated very well with process parameters (P<0.0001), resulting in models with high coefficient of determination for ellagic acid yield (r(2)=0.9636). The combinations of enzymes appeared more effective for ellagic acid production than the single enzyme did. The yield of ellagic acid from non-heat-treated acorn fringe by the use of enzymes in general increased, compared with that from heat-treated material. The research opens a technological-efficient way and develop easily-available renewable raw material for ellagic acid production.