512 



Scientific Proceedings (132) 



252 (2212) 



Studies on quantitative determination of fat in micro-organisms. 



By A. G. BENTON. 



[From the Department of Bacteriology, University of Minnesota, 

 Minneapolis, Minn.] 



Great difficulty is experienced in extracting fat from wet or 

 dried micro-organisms. It has been suggested that a large por- 

 tion of the fat they contain may he held in physical or chemical 

 combination by some ingredient of the protoplasm and various 

 preliminary treatments have been developed to free it from such 

 combination. Three of the simplest are that of Larson and 

 Larson for bacteria 1 which depends on simultaneous drying and 

 extraction by acetone, followed by ether extraction of the solid 

 residue and the acetone extract ; I. S. MacLean's method used on 

 yeast 2 which consists in boiling with normal HC1, washing and 

 then extracting with ether in a Soxhlet; and the method devel- 

 oped by C. R. Smith for work on edible pastes, in which he boils 

 the sample with alcoholic ammonia, and then extracts with ether. 



The work here reported was done on Oidium Lactis. In the 

 first experiment a two weeks' growth was drained by suction 

 and divided into three portions, one of which was treated by 

 each of the above methods without previous drying. The resi- 

 dues as well as the extracts were dried to constant weight and 

 the total dry weight of the samples obtained by addition. The 

 MacLean method is impractical on moist samples, as an unman- 

 ageable mucilaginous brown material results from the acid treat- 

 ment. The acetone method gave 1.21 per cent, ether extract; 

 the alcoholic ammonia method gave 6.13 per cent. No further 

 studies were made on the lipoids thus extracted, as drying to 

 constant weight, either in an oven at 100° or in a vacuum dessi- 

 cator over P 2 O r > at room temperature, results in a hard, semi- 

 transparent brown material, insoluble in petroleum ether, only a 

 portion of which is soluble in ethyl ether. 



In another experiment, a three weeks old growth was spread 



i Jour. Inf. Dis., 1922, xxxi, 407. 

 ZBiochem. Jour., 1922, xvi, 370. 



