Table VIII. Comparison of Sapwood and Heartwood Wood species Chip0 source White Birch Spruce Sap-Heart-wood& wood& wood6 wood6 wood6 wood6 Yield, % 44.4
A small laboratory fermentor which employs mechanical agitation for the dispersion of air introduced under pressure has previously been described by Feustel and Humfeld (1946). This fermentor has an operating capacity of 500 to 2,000 ml and has been found very useful for small-scale, yeast-culturing investigations, as well as for studies on the production of subtilin activity by Bacillus subtilis (1947). Certain limitations, however, principally those of capacity and effectiveness of foam breaking, have led to the development of an improved fermentor having a larger capacity and a more effective mechanical foam breaker. This fermentor also has a stirring device, which is so designed that air for the aeration of the culture liquid can be drawn in from the atmosphere by suction created behind the stirring blades, as compared with air introduced under pressure. This paper describes the improved fermentor and some of the preliminary results obtained. DESCRIPTION OF THE FERMENTOR The fermentor vessel consists of a standard pyrex glass jar, 12 inches in diameter and 24 inches high. This jar is fitted with a gasketed, stainless-steel cover. The stainless-steel agitation-aeration assembly shown in figure 1 is suspended from the cover and is inserted in the pyrex jar. Agitation and aeration are accomplished by means of a special air-dispersing device, mounted at the lower end of the stirring shaft near the bottom of the fermentor. Two adjustable truncated cones 31 inches in diameter are mounted on the shaft above the agitation-aeration device. By inverting these cones the stirring characteristics may be changed. Four metal struts are attached at right angles to the cover at equidistant points around the periphery of the cover, approximately 1 inch from the edge. A metal web fastened to the lower end of these struts furnishes rigidity and support for the stirring shaft. The agitation-aeration device consists of a short, central, hollow cylinder, to which four sets of tubes are fastened. These tubes are bent in the form of arcs at right angles to the cylinder. A small vane is attached to each alternate set of tubes. This device rotates between two plates. The upper plate is attached to the supporting web described above. The lower plate is attached to, and kept parallel with, the upper plate by studs. The lower plate has a large circular hole, through which the culture liquid enters. An air-intake pipe extends from the cover to a point directly below the hollow, central core of the agitation
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