Patent GB-448689-A (GB)
Title: Method and apparatus for the production of yeast and for the fermentation of solutions
IPC: C12M1/08
Filed: 1934-09-12
Abstract: 448,689. Yeast; fermentation processes. SCHOLLER, H., Solln, near Munich, and EICKEMEYER, R., Tornesch, Holstein, both in Germany. Sept. 12, 1934, No. 26240. [Class 14 (ii)] In the production of yeast and the fermentation of solutions the fermentation liquid is made to stream continuously or periodically in vertical paths through a fermentation chamber, the flow of the liquid circulating in the fermentation space being regulated as regards its direction and velocity by means including a system of vertical and inclined surfaces, in such a way that the yeast is partially held in suspension and partly deposited on the inclined surfaces, slides downwardly thereon, and is then wholly or partially resuspended in the fermentation liquid at a suitable place. The process is carried out with very high yeast concentrations. The resuspending of the yeast which settles on the inclined surfaces may be effected by mechanical devices or by stirring with air or other gases. A portion corresponding with the rate of yeast growth is gathered from the settled yeast and removed intermittently or continuously through a sluice arrangement. If desired, the yeast concentration can be kept constant in this way. The fermentation vessel is divided by vertical surfaces into three zones, a suspension zone 50 in which the yeast is kept in suspension by upwardly flowing liquid, an optional circulation zone 51 by which the liquid which does not go to the settling zone 52, and if desired some liquid from the latter also, is returned to the suspension zone, and the settling zone 52 in which the velocity of flow is retarded or reversed. The cross-section of the suspension zone is such that the velocity of flow is automatically greater therein than in the settling zone. The recirculation of yeast back to the suspension zone to maintain a high yeast concentration therein is effected by giving additional upward motion to the liquid in this zone, by means of a propeller stirring mechanism which can also serve to subdivide the excess yeast mud, or by blowing in gases, especially by fine aeration, or otherwise. Two embodiments are described in detail in which two different systems of circular or prismatic vertical and inclined surfaces are arranged in the settling zone. The velocity of flow of the liquid is preferably adjusted so that the time of flow just gives the yeast opportunity to settle. In one of the embodiments the surfaces in the settling zone are vertical, adjustable flaps being arranged in one of the channels of flow to enable the motion of the liquid to be regulated. In the other modification a prismatic instead of a funnel-shaped trough is employed, and a more complicated system of vertical and inclined surfaces, including inclined baffles and funnel-shaped devices, is arranged in the settling zone. In both embodiments means for the inlet and outlet of the fermentation liquid and for the admission of air are provided. In one method of working, the flow through the apparatus and the yeast concentration are regulated so that part of the micro-organisms suspended in exhausted fermentation liquid leaves the vessel in order, for the purpose of effecting further working up by one or more similar treatments, several apparatuses of the type described being arranged in series or in parallel. Known methods for promoting the flocculation of micro-organisms, such as the addition of alkali to lower the pH value, the production of phosphate precipitates, and the action of bacteria such as flock lactic acid bacteria may be employed. The method may be employed when working up nutrient solutions such as wood sugar liquors containing substances which check fermentation.