The response surface methodology for optimization of tyrosinase immobilization onto electrospun polycaprolactone-chitosan fibers for use in bisphenol A removal.

Composite polycaprolactone-chitosan material was produced by an electrospinning method and used as a support for immobilization of tyrosinase by mixed ionic interactions and hydrogen bonds formation. The morphology of the fibers and enzyme deposition were confirmed by SEM images. Further, multivariate polynomial regression was used to model the experimental data and to determine optimal conditions for immobilization process, which were found to be pH 7, temperature 25 °C and 16 h process duration. Under these conditions, novel type of biocatalytic system was produced with immobilization yield of 93% and expressed activity of 95%. Furthermore, as prepared system was applied in batch experiments related to biodegradation of bisphenol A under various remediation conditions. It was found that over 80% of the pollutant was removed after 120 min of the process, in the temperature range 15-45 °C and pH 6-9, using solutions at concentration up to 3 mg/L. Experimental data collected proved that the stability and reusability of the tyrosinase were significantly improved upon immobilization: the immobilized biomolecule retained around 90% of its initial activity after 30 days of storage, and was still capable to remove over 80% of bisphenol A even after 10 repeated uses. By contrast, free enzyme was able to remove over 80% of bisphenol A at pH 7-8 and temperature range 15-35 °C, and retained less than 60% of its initial activity after 30 days of storage

Electrospun biosystems made of nylon 6 and laccase and its application in dyes removal

Electrospun materials, due to the possibility of design of their properties, are suitable as supports for enzyme immobilization. Produced biocatalytic systems might be then apply in various biocatalytic reactions, including conversion of pollutants. In our study, electrospun fibers made from nylon 6 was produced, modified and applied as a support for laccase immobilization by adsorption and covalent binding. The systems with immobilized laccase were used in decolorization process of selected dyes, azo dye Reactive Black 5 and the anthraquinone dye Reactive Blue 4. It was found that at from dye solution at concentration 1 mg/L at pH 5, temperature 25 °C, after 24 h of process the efficiency of decolorization of Reactive Blue 4 and Reactive Black 5 reached 77% and 63%, respectively. The storage stability studies showed that after 30 days of storage, the relative activities were 60% and 95% for adsorbed and covalently bonded oxidoreductase respectively. Moreover, after 10 consecutive catalytic cycles adsorbed and covalently bonded laccase retained over 60% and 70% respectively, indicating the possibility of application of the obtained systems on a larger scale for removal of phenolic pollutants from wastewaters