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Keywords:

  • pregastric esterase;
  • anhydrous milkfat;
  • lipolyzed butteroil;
  • hollow-fiber reactor;
  • immobilized lipase;
  • selective release of fatty acid residues

ABSTRACT

Pregastric esterases derived from the salivary tissues of kid goats and lambs were immobilized by physical adsorption in a continuous flow, hollow-fiber reactor and subsequently used to hydrolyze anhydrous milkfat, thereby producing lipolyzed butteroils. These 2 esterases were used in separate trials conducted at temperatures of 40 °C, 45 °C, and 50 °C and pH values of 5.0, 6.0, and 7.0. High-performance liquid chromatography (HPLC) was used to determine the relative proportions of the different fatty acid residues released as functions of the reactor space time for the indicated operating conditions. For both esterases, the rates of the lipolysis reactions were fastest at 40 °C and a pH of 6.0. The rates of release of the native individual fatty acid residues were modeled using expressions of the generalized Michaelis-Menten form based on a ping pong bi bi mechanism. Nonlinear regression analyses indicated that for both esterases, the experimental data were consistent with the form of the ping pong bi bi mechanism for which the rate controlling step is deacylation of the enzyme.