The native Celluclast BG cellulase enzyme complex consists of different enzymes which can also degrade great substrate molecules as native celluloses. This enzyme complex has been covered by a very thin, a few nanometers thick, polymer layer, in order to improve its stability. It has been proved that the polymer layer around the enzyme molecules does not hinder the digestion as great substrates as crystalline cellulose polymer. The stability of the prepared enzyme nanoparticles (PE) could significantly be increased comparing to that of the native one what was proved by results of the total cellulose activity measured. The pretreated enzyme complex holds its activity often a few magnitudes of orders longer in time than that of the native enzyme complex (enzyme without pretreatment). It retains its activity at least ten times longer than that of the native one, at a temperature range between 20 and 37 A degrees C. The pretreated enzyme complex can have about 50 % of its original activity during 12 h of incubation at even 80 A degrees C, while the native cellulase one totally lost it during 6 h incubation time. The activity of PE has not been significantly reduced even at extreme pH values, namely in the pH range of 1.5 to 12.