The effect of lanthanum (III) on the activity of xylanase by Penicillium and its influence on brightness in the paper pulp bleaching

Xylanase is widely used in pulp and paper bleaching. In this study, the effects of rare earth ions (La3+, Ce3+, Er3+ and Gd3+) on the activity of xylanase produced by Penicillium are investigated and the application of a xylanase solution containing La3+ in paper bleaching is presented. Our results indicate that the bleaching effect of the enzyme solution containing La3+ was markedly better when the concentration of La3+ was 10(-8) g/L after 4 days of incubation. The mechanism of lanthanum on the improvement of xylanase activity was revealed through electrical conductivity, atomic absorption spectrometer, infrared spectroscopy and fluorescence microscopy analyses. The PCR result clearly demonstrates that a low concentration of La3+ led to the transversions of three base pair of gene sequences. Our experiment also reveals that the La3+ may have been involved in the cellular metabolic processes of Penicillium and intervened in the base pairing and DNA replication. This research may provide new insights into the improvement of enzymatic activity by lanthanum (III) and its application in paper pulp bleaching.