Improvement of tylosin fermentation by mutation and medium optimization.

A tylosin-hyperproducing mutant of Streptomyces fradiae MNU20 was isolated from 3500 strains obtained from either MNNG- or u.v.-treated S. fradiae NRRL2702. With the optimal medium, S. fradiae MNU20 was able to produce 159 mg tylosin g biomass(-1), indicating the tylosin productivity in S. fradiae NRLL2702 was increased 14-fold by mutation and medium optimization. When the effect of valine, succinate and natural zeolite on tylosin production was investigated sing the optimal medium, these substances essentially enhanced tylosin production up to 349 mg g biomass(-1); their time addition during the culture period appeared to be critical for the increase.

Quantitative analysis of mycelium morphological characteristics and rifamycin B production using Nocardia mediterranei.

Rifamycin B production in batch culture of Nocardia mediterranei was compared with mycelium morphological changes. Rheological behaviour of batch culture medium was identified and various rheological parameters were evaluated in order to characterize quantitatively the morphological changes. Rifamycin B production kinetic parameters in the batch culture were also calculated and the parameters were compared with the rheological parameters. Consequently, specific rifamycin B production rate (qrif) was closely related to yield shear stress (tau 0) and to morphological factor (delta*). Both parameters are considered to be important for the production control of rifamycin B.

Kinetic characterization of sporulation in Streptomyces albidoflavus SMF301 during submerged culture.

We report the first quantitative analysis of the relationship between environmental changes and sporulation of a streptomycete, Streptomyces albidoflavus SMF301, in submerged culture. A chemically defined medium was constructed for sporulation, over 10(9) spores ml-1 being formed in the submerged batch culture. Kinetic parameters calculated from batch and chemostat cultures showed that specific submerged spore formation rate (qspo) was inversely related to the specific mycelial growth rate (mu). The optimum growth rate for submerged spore formation was 0.05 h-1, when the maximum value of qspo was 1.0 x 10(6) spores g-1 h-1. The turnover rate of biomass at maximum growth yield was 0.029 h-1, when 5.6 x 10(6) spores were formed from 1 g mycelium. The present quantitative analysis of submerged spore formation using a controlled system opens the way for biochemical and molecular biological studies related to the morphological differentiation of Streptomyces spp.