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The Action of Microorganisms on Fats. II. Some Characteristics of the Lipase System of Penicillium Roqueforti¹

Department of Dairy Husbandry, University of Minnesota, St. Paul

ABSTRACT

The lipolytic activities of preparations obtained from mycelia of P. roqueforti and from the medium on which the mold was cultured have been investigated. The effects of temperature, pH, type of substrate, and sodium chloride concentration on lipolytic activity also have been studied.

The temperature optima of the mycelial and medium preparations on tributyrin and butterfat were between 30 and 32° C. with a reaction time of 1 hour. At low temperatures, an increase in temperatures increased the rate of hydrolysis markedly.

The pH-activity curves as influenced by a variety of experimental conditions have been described. The pH optima obtained were as follows: medium preparation, pH 7.0 to 7.8 on tributyrin and 6.5 to 6.8 on butterfat; mycelial preparation, 6.0 to 6.7 on tributyrin and 7.0 to 7.2 on butterfat.

The lipolytic enzymes present in these two preparations show much greater relative specificity for triglycerides than for ethyl esters. There was consistently a faster rate of hydrolysis by the enzyme system acting on tributyrin than on any other substrate used. The activity was also greater on ethyl butyrate than on the other ethyl esters studied.

The lipase system was about one-third as active on butterfat as it was on tributyrin. The activity of this lipase system acting on both triglycerides and ethyl esters decreased as the molecular weight of the fatty acid esterified with the alcohol increased. Differences in characteristics of the two enzyme preparations constitute additional confirmation that there may be more than one lipase present in this mold. An increase in sodium chloride concentration decreased the activity of this lipase system.

¹ The data in this paper are from a thesis presented by the senior author in partial fulfillment of the requirements for the degree of Doctor of Philosophy, University of Minnesota. Scientific Journal Series Paper 3008. Minnesota Agricultural Experiment Station.