The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase
The polypropylene for preparing packing(biofilm carrier) used in biodegradation of wastewater was modified by adding some biocompatible, hydrophilic and magnetic additives such as stearic acid, polyvinyl alcohol, activated carbon and magnetic powders.The prepared packing was then magnetized in a magnetizer to be charged with a 2.5×10 -3 —5.0×10 -3 tesla permanent magnet.The wettablity and biofilm formation performance of the modified and magnetized packing were tested.The result showed that the adsorbed water content of the polypropylene packing increased more than 300% and the period of biofilm formation reduced from 7—9 days to within 2 days after modification and magnetization.The removal rate of COD Cr by the modified and magnetized packing was also proved to be 30% higher than that by the original polypropylene packing.
