CHANGE OF MYCELIAL MORPHOLOGY IN TYLOSIN PRODUCTION BY BATCH CULTURE OF STREPTOMYCES-FRADIAE UNDER VARIOUS SHEAR CONDITIONS

Morphological change during culture of the tylosin producer Streptomyc es fradiae under various shear conditions was investigated using an im age analysis system. The morphology was classified as filament, entang led filament, or pellet by measuring the mycelial area and convex peri meter. At fermenter agitation rates of 400 rpm and higher, filament an d entangled filament morphology comprised more than 50%. How-ever, in cultures at agitation rates lower than 400 rpm, pellet morphology incr eased gradually and until it comprised more than 50%; in an air-lift r eactor, the pellet ratio reached 80% after 160-h culture. The average areas of pellets and mycelia in the air-lift reactor were respectively 100- and 20-fold those under high shear condition. Both pellet area a nd mycelial morphology changed during the culture period according to the shear conditions. Among the various sheer conditions, tylosin prod uction and rapeseed oil consumption were lowest in the air-lift fermen ter culture with against in the fermenter at 400 rpm. From the viewpoi nt of tylosin production, the optimal mycelial area that gave the maxi mum production rate under various shear conditions was around 4 x 10(3 ) mu m(2). When the mycelia and pellet areas exceeded 4 x 10(3) mu m(2 ), the tylosin production rate decreased drastically.