Purification and characterization of the pectin lyase and protease produced by Penicillium velutinum grown on Eichhornia crassipes under solid state fermentation

Penicillium velutinum van Beyma grown on water hyacinth Eichhornia crassipes (Mart.) Solms. wastes as a rich organic source under conditions of solid state fermentation was selected in a preliminary screening for producing interesting levels of pectin lyase (PL) and protease. Addition of some natural additives to the fermentation medium improved the potentiality of enzymes production. PL and protease secreted by P. velutinum under these conditions were purified to electrophoretic homogeneity using ammonium sulphate fractionation and 2-step-column chromatography. The purified PL expressed its maximal activity at 50 degrees C and pH value of 5.5, showed good stability in the pH range of 5.5 to 6.0 and its midpoint of thermal inactivation (Tm) was 65 degrees C after 45 min of exposure. Protease expressed its maximal activity at 65 degrees C and pH value of 7.0, showed good stability in the pH range of 6.5 to 7.5 and its Tm was 75 degrees C after 45 min of exposure. Ions of Ca, Na and K showed a stimulatory effect and ions of Zn and Mn showed an inhibitory effect. Moreover, Ag and Hg showed complete inhibitory effect on the two enzymes activity. Molecular mass of the purified PL and protease was found to be 42 and 63 kDa respectively.