Pectolytic enzyme production by Phoma betae

Abstract

Phoma betae from decayed sugar beet storage root tissue grew most rapidly in culture at 15C but produced more polygalacturonase (PG) at 20C. When the fungus was supplied with six different nitrogen sources, it produced the most PG on (NH4)2SO4.Assays of dialyzed culture filtrates using sodium polypectate and pectin or cell wall material from storage roots as the carbon sources showed the production of exopolygalacturonase (exo-PG) and endopolygalacturonate trans-eliminase (endo-PGTE). No pectin methyl esterase was detected. Exo-PG and endo-PGTE also were present in decayed sugar beet tissue. Only endo-PGTE was detected within 3 mm of tissue surrounding the rotted area.In culture, cell wall material from the susceptible variety A58 induced more endo-PGTE formation than the resistant 2B. But 2B induced more exo-PG formation than A58. It is suggested that endo-PGTE plays a major role in cell wall degradation because pH 7.5 was optimum for tissue maceration and pH 8.5 for enzyme activity and the advancing margins of rotted tissue contained only endo-PGTE.