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Journal of Dairy Science Vol. 46 No. 3 186-189
© 1963 by American Dairy Science Association ®
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Distribution of Diacetyl Reductase among Bacteria1

E. W. Seitz2, W. E. Sandine, P. R. Elliker and E. A. Day

Departments of Microbiology and Food Science and Technology, Oregon State University, Corvallis

ABSTRACT

This work was undertaken to determine comparative amounts of the enzyme diacetyl reductase in several strains of lactic streptococci and Leuconostoc species. The level of enzyme in cultures of Pseudomonas, Alcaligenes, and coliform bacteria also was examined. Among the lactic streptococci, Streptococcus diacetilactis strains were the most active in reducing diacetyl; one strain contained 100 units of diacetyl reductase per milligram of enzyme protein. Strains of Streptococcus lactis, Streptococcus cremoris, Leuconostoc citrovorum, and L. dextranicum tested were comparatively inactive in diacetyl reduction; these bacteria contained from zero to eight units of enzyme per milligram of protein. From this, the importance of selecting strains containing little or no diacetyl reductase for use in maximum flavor-producing mixed-strain lactic streptococcus starter cultures was indicated. With the exception of one strain each of Escherichia coli and Pseudomonas viscosa, the coliform, Pseudomonas and Alcaligenes organisms showed considerable diacetyl reductase activity; Aerobacter aerogenes 8724 contained 345 units per milligram of enzyme protein. These results emphasized the consequences of contamination of dairy products by diacetyl reductase-containing bacteria in terms of flavor loss. Possible uses of the enzyme for removal of diacetyl from fermented beverages and citrus juices are mentioned.

FOOTNOTES

1 Technical paper no. 1605, Oregon Agricultural Experiment Station. Supported in part by a grant from the American Dairy Association.

2 Present address: Dairy Technology Research Institute. Central Experimental Farm, Ontario, Canada.






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