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Distribution of Lipase among Components of a Water Extract of Rennet Casein¹

Department of Dairy Technology, The Ohio State University, Columbus

ABSTRACT

Diethylaminoethyl cellulose (DEAE) and Sephadex G-25 chromatographic techniques were used to investigate the distribution of milk lipase activity among the components of casein by their application to a water extract of rennet casein, in which the specific lipase activity was approximately 11 times greater than that of skimmilk.

The eight fractions obtained from the casein extract by an eight-step gradient DEAE-cellulose ion exchange procedure and the three fractions obtained by Sephadex G-25 Gel filtration exhibited lipase activity. For the DEAE-cellulose method, seven of the eight fractions had specific activities greater than that of the original skimmilk, with Fraction 7 exhibiting specific lipase activity approximating a 1,000-fold increase. For the Sephadex G-25 fractions, and in comparison to the original skimmilk, the relative specific activities of the first fraction were about twice as great, and the specific activities of the second and third fractions were 50–150 times greater than skimmilk.

The concentration of lipase was increased three to six-fold in Sephadex Fractions 2 and 3 when the extract of rennet casein was frozen, dried, then reconstituted prior to Sephadex gel filtration.

Fractionation by either DEAE-cellulose or Sephadex-25 gave lipase activity equivalent to about 160% of the original activity in the water extract of casein.

¹ Article 14:65. The Department of Dairy Technology. This investigation was supported by Public Health Service Grant no. EF-00206-02 from the Division of Environmental Engineering and Food Protection.