Tanzania Journal of Agricultural Sciences, 1998; I (2): 141-148A stlldy was conducted to compare the efficiency of two methods of microbial cell separation and enzyme purification using penicillin-G-acylase (PGA) from Escherichia coli. The efficiency of two methods of ceJ[ separation; centrifugation and cross flow filtration (CFF) were compared. The CFF method was found to have both higher separation efficiency and enzyme yield than centrifugation method. Centrifugation method gave a separation efficiency of 98.5% with enzyme yield of94 % whereas CFFmethod resulted in 100% separation efficiency and enzyme yield of98.8%. The Escherichia coli cells were disrupted by high pressure homogenization (HPH),and the disrupted cells were purified using two different techniques. Technique I was a combination of cross-flow-diafiltration (CFD) , ultrafiltration (UF) and heat/pH-shift treatments. This technique resulted in 47% enzyme yield with a purification factor of 12. Technique II which involved two extraction steps by' aqueous two - phase system (APS) coupled with UF resulted in 62 % enzyme yield with a pu;ificationfactor of 4. Technique I was therefore much better than techriique Il in purifying the enzyme. For higher enzyme yield, technique II would seem to be a better one than technique I.