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To find out the optimum conditions for the cell growth and the synthesis of PHB in A. eutrophus, the effects of culture conditions and extracellular by-products were investigated. Glucose and (NH,)2HP0, were optimum carbon and nitrogen sources, respectively for cell growth of A. eutrophus. PHB accumulation was stimulated by deficiency of nutrients such as NH,-, P0,3-. and Mg" in the medium. NH;deficiency was the most suitable for PHB accumulation and PHB accumulation ratio was reached 42% of dry cell weight. The specific growth rate was increased 1.5 times by addition yeast extract in the medium, and proteins and vitamins are supposed a main factor of that effect. The extracellular products such as ethanol and butanediol were excreted under anaerobic conditions. And ethanol was found to decrease the specific growth rate.
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