| 摘要 |
1,168,832. Yeast. BRITISH PETROLEUM CO. Ltd. Jan.13, 1967 [Feb. 3, 1966], No.4765/66. Heading C6F. A straight chain hydrocarbon-consuming yeast is cultivated in the presence of a petroleum fraction consisting wholly or in part of straight chain hydrocarbons, in the presence of an aqueous nutrient medium consisting in part of phosphate and in the presence of a gas containing free oxygen, the petroleum fraction and the aqueous medium being continuously fed to a fermenter containing the yeast and wherein a first stage of cultivation of yeast takes place at a pH in the range 4 to 5, and a product stream comprising the yeast is continuously passed to a second stage fermenter wherein the yeast is treated with a second stage aqueous nutrient medium and is cultivated at a pH of about 5‹5, a product stream comprising yeast being continuously removed from the second stage fermenter, and in the first stage of cultivation the amount of phosphate in the aqueous phase in the first stage fermenter is such that the rate of growth of the yeast is not impeded by shortage of phosphate and in the second stage the amount of phosphate in the aqueous phase in the second stage fermenter is less than the amount required for unimpeded growth of the yeast in the first stage fermenter or phosphate is absent from the aqueous phase of the second stage fermenter. The product stream from the second fermenter may be treated to recover the yeast. The second stage aqueous nutrient medium may contain or consist of all or part of the aqueous nutrient medium withdrawn from the first stage fermenter. The aqueous nutrient medium supplied in a given period to the second stage fermenter should contain less than 1 part by weight of phosphate (estimated as elemental phosphorus) per 100 parts by weight of yeast (estimated at dry weight) introduced into the fermenter in the period. Phosphates: Water soluble ammonium or metal phosphates, or a phosphoric acid, such as sodium triphosphate and ortho-phosphoric acid. |
