LIPID PRODUCTION BY A SOIL YEAST
ROBERT L. STARKEY'
New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick, New Jersey

Received for publication August 30, 1945

It has been well established that fatty substances are produced by various microorganisms, notably by certain yeasts and filamentous fungi as well as by the tubercle bacilli and a species of Azotobacter. The tubercle bacilli and other acid-fast bacteria contain from 20 to 40 per cent lipid on the dry-weight basis
(Anderson, 1939). Even some of the common non-acid-fast bacteria may contain considerable amounts of lipid. Escherichia coli, Staphylococcus albus, and
Bacillus megatherium were found to contain from 8 to 40 per cent lipid when grown on certain media (Larson and Larson, 1922). More commonly, however, the lipid content of bacteria has been reported to be below 10 per cent. The results of Gorbach and Sablatnog (1934a, 1934b) may be cited in this connection.
They found that whereas the lipid content of Pseudomonas aeruginosa was 0.6 per cent when grown on meat extract agar at pH 7.0, there was as much as
3.9 per cent lipid when the organism was cultivated on mannitol. Anderson
(1939) reported 2 to 6 per cent lipid in cells of Phytpmonas tumefaciens and 7 per cent in Lactobacillus acidophilus.
Among the bacteria, Azotobacter indicum is unique in lipid production (Starkey and De, 1939). The cells of this bacterium commonly contain two large fat globules, one at each end of the rod-shaped cells, and as much as 50 per cent of the cell volume is occupied by the fat globules.
The lipid content of filamentous fungi ranges between 1 and 40 per cent, and differs with the various cultures and the conditions under which they are grown.
(Pruess, Eichinger, and Peterson, 1934; Prescott and Dunn, 1940; Bloor, 1943).
The lipid content of 24 filamentous fungi studied by Pruess and Strong (1933) was from 1 to 25 per cent with an average between 6 and 9 per cent. Ward,
Lockwood, May, and Herrick (1935) determined the lipid content of 61 fungi and reported that six of the fungi contained over 20 per cent lipid. Under favorable conditions of cultivation, Penicillium javanicum was found to contain as much as 41.5 per cent. Large amounts of lipid were produced by species of
Oospora Wallroth when grown on milk, and the results of Geffers (1937) indicate that this organism can be used to synthesize fat from milk wastes. Up to 50 per cent of the mycelium could be extracted with fat solvents.
Attention was focused on lipid production by yeasts and related organisms through the results of Lindner and associates, who developed a process for the production of fat from carbohydrates by Endomyces vernalis in Germany during
World War I (Fink, Haehn, and Hoerburger, 1937; Prescott and Dunn, 1940).
When cultivated under conditions favorable for lipid production, this yeast con1 Journal Series Paper of the New Jersey Agricultural Experiment Station, Rutgers
University, Department of Microbiology.
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ROBERT L. STARKEY

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tained as much as 44.7 per cent lipid; but when cultivated on a production scale, there was about 20 per cent lipid. Heide (1939), who recently studied the influence of medium composition on lipid production by Endomyce8 vernallis, found as much as 42 per cent lipid in the cells under conditions favorable for lipid accumulation.
Several yeasts were studied by Rippel (1943) for lipid production, among which was Nectaromyces reukaufii, which produced 10 to 15 g of lipid for each 100 g of carbohydrate decomposed.
The results of Heide (1939) and others (Bichkovskaya, 1939; Prescott and
Dunn, 1940; Raaf, 1941-1942; Rippel, 1943) indicate that conditions favorable for maximum lipid content of yeast are not those giving the maximum conversion of the carbon source of the substrate to lipid. Cells grown in media rich in nitrogen give high yields, but their lipid content is low; media deficient in