inoculation rate is 5 ml of seed inoculum per 100 ml of fermentation medium a series of 500 ml erlenmeyer flasks containing sterile fermentation medium consisting of the following ingredients ______________________________________glucose monohydrate 10 g ldextrin 20 g lcorn steep liquor 2 5 g lnh sub 4 no sub 3 3 0 g lnacl 2 0 g lcaco sub 3 5 0 g lph 7 2 presterilization ______________________________________ the fermentation flasks are incubated at a temperature of 28 u00b0 c on a gump rotary shaker operating at 250 rpm and having a 21 2 inch stroke harvest is usually after about 5 days of fermentation a typical 5 day fermentation has the following titers of antibiotic in the fermentation broth in the assay results a biounit bu is defined as the concentration of the antibiotic which gives a 20 mm zone of inhibition under the standard assay condition thus if for example a fermentation beer has to be diluted 1 100 to give a 20 mm zone of inhibition the potency of such beer is 100 bu ml the whole beer ca 5 000 l from a fermentation as described above is adjusted to ph 7 3 with naoh and filtered on a 30 inch filter press using diatomaceous earth as a filter aid during the filtration operation wash water is applied to the filter cake from the filtration operation is recovered 5 500 l of clear fermentation browth which is then extracted twice with methylene chloride 1 400 l each time to give a total of 2 800 l of solvent extract this solvent extract is concentrated.