RESUMEN
The technique of double-layered plate was developed for screening the library of mutant endoglucanase III from Trichoderma reesei generated by the method of directed evolution.The enzyme activity was determined according to the velocity of the formation of halos on the plates.Several mutants with higher activity than the wild type at low temperature or alkaline pH were obtained by using this strategy under different screening conditions.Further results of spectrophotometric determination of the activities of these mutants were consistent with the results of plate screening.The establishment of such strategy will broaden the applications of the directed evolution methods for improving the existing proteins to obtain useful enzymes with new properties for industrial applications.