“…Many studies have been conducted using electrophoresis as a tool to differentiate between Penicillium ssp. isolates, such as: Grassin & Fauquembergue (1996); Banke et al, 1997;Dupont et al, 1999;Boysen et al 2000;Chávez et al, 2002;Samson et al,2004;Cho et al. 2005;Bakri et al, 2007;Cardoso et al, 2007;Xi et al, 2007;Abulhamd, 2009;Redondo et al, 2009;Inkha & Boonyakiat, 2010;Roslan et al, 2010;Elhariry et al, 2011;Francis et al, 2011;Mohammad et al, 2011 andTiwari et al, 2011. In this study, biochemical assay was performed on 14 isolates of Penicillium species that had been previously collected from different localities and habitats in Jeddah, Saudi Arabia and cultivated on two different media: Czapek Dox ' s medium in which NaNO3 is the source of inorganic nitrogen and Waksman's medium in which pepton is the source of organic nitrogen.…”