The range of morphological forms of actinomycetes in shaken flask culture and fermenters is reviewed. Some of the factors that influence pellet formation and its prevention are discussed. The relationship between morphology and production of antibiotics and other metabolites is also examined.
The production of alpha-amylase (alpha-1,4-glucan 4-glucanohydrolase; EC 3.2.1.1) by a strain of Bacillus stearothermophilus isolated from leaf litter was investigated in a tryptone-maltose medium at 55 degrees C in batch and chemostat culture. Amylase production was growth-limited and restricted to the exponential phase in batch culture. The enzyme yield was reduced by 40% when the culture pH was maintained at pH 7.2. Amylase production in chemostat culture was influenced by the growth rate throughout the dilution rate range used.
The morphology of 49 Streptomyces strains and eight other actinomycetes was studied in shaken liquid culture, using a range of spore inocula in a complex medium. Results showed that each strain would produce one, two, or more different gross morphological types throughout the spore inoculum range tested. The morphological forms that were observed included compact pellets, spiky or fluffy pellets, oblong pellets, flakes, hydrophobic rafts, aggregates, dispersed mycelium, fragmented mycelium, or combinations of these forms. Two strains of S. viridochromogenes developed different ranges of morphology in the test conditions.Key words: Streptomyces, pellets, spore inoculum.
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