4. Conclusions
Escherichia coli laccase, namely cueO, is involved in the Cu ef- flux system under aerobic conditions. It was reported that this enzyme could oxidize a large number of xenobiotics of environmental importance. However, their characterization in terms of their thermal and chemical stability, as well as their stabilization by immobilization techniques, has not been reported so far. Laccase crude extract was stable up to 30 °C and alkaline pH, showing its great potential use in effluent treatment. Laccase crude extract was stabilized by entrapment in Cu alginate gels. The immobilization process extended the range of stability of the enzyme, which can be used at 50 °C without a significant loss of activity. Furthermore, the immobilized derivatives showed improved stability at different operating conditions, such as pH between 4.5 and 7, temperature from 25 to 30 °C, and a high ionic strength. These derivatives remained active under continuous operation conditions up to 430 h, retaining more than 70% of the initial activity. The immobilized biocatalyst developed was applied in the decolorization of anthraquinone, azo, indigoid and triarylmethane synthetic dyes. Higher decolorization yields at short reaction times without mediator requirements were obtained. The laccase biocatalyst exhibited improved stability in continuous operation, which confirms its versatility and potential application in industrial processes.
