Screening of three commercial plant peroxidases for the removal of phenolic compounds in membrane bioreactors

Enzymatic oxidation of phenolic compounds in coffee processing wastewater

Peroxidases can be used in the treatment of wastewater containing phenolic compounds. The effluent from the wet processing of coffee fruits contains high content of these pollutants and although some studies propose treatments for this wastewater, none targets specifically the removal of these recalcitrant compounds. This study evaluates the potential use of different peroxidase sources in the oxidation of caffeic acid and of total phenolic compounds in coffee processing wastewater (CPW). The identification and quantification of phenolic compounds in CPW was performed and caffeic acid was found to be the major phenolic compound. Some factors, such as reaction time, pH, amount of H2O2 and enzyme were evaluated, in order to determine the optimum conditions for the enzyme performance for maximum oxidation of caffeic acid. The turnip peroxidase (TPE) proved efficient in the removal of caffeic acid, reaching an oxidation of 51.05% in just 15 minutes of reaction. However, in the bioremediation of the CPW, the horseradish peroxidase (HRP) was more efficient with 32.70%±0.16 of oxidation, followed by TPE with 18.25%±0.11. The treatment proposed in this work has potential as a complementary technology, since the efficiency of the existing process is intimately conditioned to the presence of these pollutants.

Application of a diffusion-reaction kinetic model for the removal of 4-chlorophenol in continuous tank reactors

A continuous tank reactor was used to remove 4-chlorophenol from aqueous solutions, using immobilized soybean peroxidase and hydrogen peroxide. The influence of operational variables (enzyme and substrate concentrations and spatial time) on the removal efficiency was studied. By using the kinetic law and the intrinsic kinetic parameters obtained in a previous work with a discontinuous tank reactor, the mass-balance differential equations of the transient state reactor model were solved and the theoretical conversion values were calculated. Several experimental series were used to obtain the values of the remaining model parameters by numerical calculation and using an error minimization algorithm. The model was checked by comparing the results obtained in some experiments (not used for the determination of the parameters) and the theoretical ones. The good concordance between the experimental and calculated conversion values confirmed that the design model can be used to predict the transient behaviour of the reactor.

Dual-enzyme natural motors incorporating decontamination and propulsion capabilities

Self-propelled dual-enzyme natural motors display attractive decontamination and propulsion capabilities. The movement of the biocatalytic tissue motors through the contaminated sample leads to a greatly improved remediation efficiency.

Phenol biodegradation by different mixed cultures and the optimization of efficiency of the degradation

In this study, the phenol degradation capacities of four different mixed cultures, namely, Ankara Stream (AS), petroleum-contaminated soil (PS), olive mill wastewater (OMW), and drug mill wastewater (DMW) were investigated with regards to different pH levels, phenol (497.2-1183.0 mg/L) and biomass concentrations (0.5-3.0%(v/v)). The most efficient culture was selected and the optimal conditions required for its highest performance in phenol degradation were studied. We found 100% phenol degradation for DMW at nearly 1000 mg/L initial concentration. The optimum pH was 8 and the mixed culture could tolerate phenol levels up to approximately 1500 mg/L. The selected culture degraded all of the phenol concentrations ranging from 497.2 to 1183.0 mg/L with 100% efficiency after 48 h and 120 h incubation, respectively. Increasing the biomass concentration from 0.5% to 3.0% (v/v) level decreased the incubation time needed for complete degradation. The data indicate that the mixed culture used in this study can be taken as a good candidate for effective treatment of waters contaminated by phenol.