GB1208572A - Improvements in or relating to the cultivation of micro-organisms - Google Patents

Abstract

1,208,572. Recovering yeast &c. BRITISH PETROLEUM CO. Ltd. Feb. 8, 1968 [March 8, 1967], No. 10827/67. Heading C6F. A material consisting of, or containing, a major proportion by weight of a micro-organism and a minor proportion of a hydrocarbon is heated under conditions such that the cell walls of the cells of the micro-organism undergo change but such that after the heat treatment a major proportion of the cells remain intact cells i.e. cells which retain their cytoplasm within their cell walls. Examples and comparative experiments demonstrate that the phosphorus and ash contents of the yeast product are lower when the heat treatment is included. According to an example, the product stream from the cultivation of Candida tropicalis on a gas oil in the presence of an aqueous nutrient medium and a free oxygen-containing gas, was decanted to remove aqueous phase. Fresh water was added to the yeast cream in order to reconstitute the original mixture, a small proportion of a lauric alcohol oxyethylenated and sulphated detergent was added to the mixture and stirred, and the emulsion produced was centrifuged to give a gas oil phase, an aqueous phase and a yeast paste. The yeast paste, diluted with water, was heat treated at a temperature of 100‹ C. for one hour in a vessel equipped with a propeller and then centrifuged hot. The yeast slurry thus obtained was dried to a cream in a drum drier, and the cream (containing 50% by weight of yeast) was twice extracted with a solvent mixture consisting of equal parts by weight of n-hexane and isopropanol firstly at 80‹ C. for 30 minutes and then at 50‹ C. for 30 minutes. After filtration of the solvent loaded with some yeast impurities, the remaining product was treated with isopropanol at 50‹ C. for 10 minutes. Finally, the yeast product was dried with superheated steam and the moisture, lipid, phosphorus, ash and nitrogen contents of the yeast were determined. The proportion of intact cells in the material after the heat treatment was 95%. In further examples the heat treatment consisted of: (a) injecting steam at 50 psig to hold the temperature of the yeast at 100‹ C. for 30 minutes; (b) washing for 2 hours with hot water to maintain the yeast at 90‹ C.; or (c) heating at 70-80‹ C. for 30 minutes.