Cxv. a Wet-crushing Mill for Micro-organisms

FOR some years we have been engaged on the problem of extracting enzymes from micro-organisms. It is well known that most bacteria and yeasts carry out oxidations and metabolic processes at a rate incomparably higher than that of animal tissues. The peculiar virtue of micro-organisms as the source of enzymes is therefore self-evident. A certain amount of success has been attained in extracting enzymes from yeast. By drying yeast at room temperature and then resuspending in water it is possible to obtain in solution a large number of enzymes. This method, however, has one serious limitation. The fragile enzymes are destroyed by the drying procedure, and among the fragile enzymes are included the most fundamental catalysts of yeast oxidations such as the cytochrome oxidase and the coenzyme factor. This method of extracting enzymes from the dried organisms is not applicable to bacteria. In fact no generally satisfactory method is at present available for extracting enzymes from the bacterial cell. Knowledge of isolated bacterial enzymes is virtually confined to a few which can survive the autolysis of the cell. Our approach to the problem of enzyme extraction was made by some preliminary experiments with the Barnard & Hewlett [1911] mill for grinding micro-organisms, kindly lent by the designers. Though again applicable to yeast it proved ineffective for extracting enzymes from bacteria, principally through two limitations: (a) appreciable amounts of copper were introduced into the suspension, and (b) the capacity of the mill was too small to permit the grinding of an appreciable amount of a micro-organism in a reasonable time. We proposed therefore to construct a mill which would overcome the disadvantages of the Barnard mill. The objectives of the mill were: (1) absence of copper, (2) a capacity of about 40 ml., (3) greater rapidity of crushing, (4) elimination of heating due to friction and (5) a device for continuous circulation and replacement of the suspension fluid. The Barnard mill is essentially ball bearing, and the crushing is accomplished at the points of contact between the five balls and the phosphor-bronze pot. It occurred to us that by using a roller bearing with line contact between the rollers and the race, the efficiency of crushing might be greatly increased. The difficulty of roller bearings even of the precision type is that the clearance is never less than about 2-5,u. This means that the inaccuracies of fit would be of the same order of magnitude as the size of the average micro-organism. Dr Sears and his colleagues at the National Physical Laboratory and Mr Wise of the Hoffman Manufacturing Co., Ltd., suggested to us that zero clearance could be attained by forcing a specially tapered inner race of a roller bearing along a tapered shaft until the distance between the inner and outer races was less than the diameter of the rollers. Under these conditions the revolution of the roller is accompanied by deformation of the metal of the races at the two lines of contact. George Henry Lewes Student. 2 Beit Memorial Research Fellow.