Effect Of Lanthanon On Metabolism Of Aspergillus Niger And Mechanism Of Interaction Between Cellulase And Lanthanon

The paper chose Aspergillus niger as subject, which can secrete cellulase, especially the endo-1,4-β-D-glucanase. Firstly the paper studied the effect of lanthanon— —lanthanum and samarium on metabolism of Aspergillus niger. The growth rate of colonies in solid media, the weight of thalli in liquid media, the CMC activity and the FP activity of fermentation liquor were respectively measured before and after rare earth ions with different concentration were added to the media. The result is that with the influence of lanthanon, the growth rate of colonies in solid media was enhanced, the weight of thalli in liquid medium was increased, and the ability of producing cellulase of Aspergillus niger was elevated. Therefore, we can draw a conclusion that rare earth ions with suitable concentration added to the media can advance the speed of the metabolism of Aspergillus niger. The experiment indicated that lanthanum and samarium can accommodate the physiological conditions of cell, strengthen the permeability of plasma membrane, and hasten the transportation of signal and energy, so the biological effect of Aspergillus niger was improved.Furthermore, the paper studied the effect of lanthanum and samarium on the activity of cellulase. The operating procedure is as follows: fermenting Aspergillus niger in solid media, separating and purifying the cellulase secreted by Aspergillus niger, dealing cellulase with rare earth ions by different concentration, and mensurating the activity of endo-1,4- β -D-glucanase. The result is that lanthanum and samarium can enhance the activity of endo-1,4- β -D-glucanase, and they are the activators of cellulase. Additionally, the effect of La³⁺ on the conformation of cellulase was studied by FTIR spectroscopy, derivative, deconvolution and curve fitting methods in this paper. The result shows that after zymoprotein is modified with La³⁺, the ability of protein to form hydrogen bond was improved. Accordingly the relative content of β -sheets increases from 26.90% to 34.54%, with the decrease of relative content of random structures , from 20.61 to 13.00%. These data exhibit the changes of secondary structures of the zymoprotein, and reveal the mechanism of the activation of La³⁺ on cellulase.