MYCELIAL PELLET INTRASTRUCTURE VISUALIZATION AND VIABILITY PREDICTIONIN A CULTURE OF STREPTOMYCES-FRADIAE USING CONFOCAL SCANNING LASER MICROSCOPY

The intrastructure of mycelial pellets of Streptomyces fradiae, which produces tylosin, was visualized following labeling with fluorescein i sothiocyanate (FITC) and propidium iodide (PI) using confocal scanning laser microscopy. A PI-labeled inactive core was present inside the m ycelial pellet in both fermenter and air-lift reactor cultures. The th ickness of the active mycelial layer on the pellet surface was calcula ted from a density sliced image to be 60 and 68 mu m respectively, in the fermenter and in air-lift reactor cultures. Using image analysis, the active mycelial concentration of pellets in the fermenter culture was predicted to be 2.1 times higher than that in the air-lift reactor culture. The tylosin production rate in the fermenter reached 0.78 g/ l/d, which was 2.5-fold that in the air-lift reactor culture. These re sults indicate that the higher tylosin production rate in the fermente r culture was due to the higher active mycelial concentration in the f ermenter compared to that in the air-lift reactor.