Rate and extent of enzymatic lipolysis at subfreezing temperatures

Abstract

Little attention has been given to the effects that various freezing treatments have on rates of enzyme-catalyzed reactions in frozen systems and to the relationship between subfreezing temperatures and the ultimate extent to which a given reaction proceeds. Both of these aspects were explored using a model system consisting of lipase in an emulsion of tributyrin in water. The ultimate extent to which tributyrin was hydrolyzed decreased from 5.4% at −2 °C to 4.0% at −12 °C. Hydrolysis proceeded almost to completion at temperatures above 0 °C. Rapid freezing to −80 °C produced a substantially slower initial reaction rate at −8 °C than rapid freezing to −20 °C, or than slow freezing, regardless of the temperature nadir.