Control of Broth Viscosity in Colistin Fermentation by Bacillus polymyxa : Studies on Colistin Fermentation(III)

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The rheological properties of colistin fermentation broths were studied. The flow characteristics of broths were confirmed to be non-Bingham plastic flow.Factors affecting the apparent broth viscosity(ηap)were investigated to improve the mixing effect and oxygen transfer in colistin fermentation. During studies of culture conditions on ηap with 250-ml Erlenmeyer flasks, culture temperature was found to be a suitable factor to control the broth viscosity. The optimum temperature for controlling broth viscosity and colistin production was 32℃.The effect of ηap on colistin production was further investigated by varying agitation speed with a 5-l jar fermentor at 32℃. The optimum region of agitation speed was found to be 600-700 rpm, resulting in colistin production of 45,000 u/ml. On the other hand, the dilution of culture broth with sterilzed water was examined to decrease the value of ηap. However, no improvement of colistin production by the dilution of broth was observed at higher agitation speeds.From these resullts, we concluded that temperature was the most effective factor to improve colistin production from the viewpoint of production-scale.
公益社団法人日本生物工学会の論文
1983-12-25