Modification of milkfat physical properties by immobilized Pseudomonas fluorescens lipase
1997
Lee, P. | Swaisgood, H.E.
A bifunctional fusion protein was constructed by fusion of the streptavidin gene from Streptomyces avidinii to the lipase gene from Pseudomonas fluorescens, and the resulting streptavidin-lipase was expressed in Escherichia coli. Immobilized streptavidin-lipase was prepared by direct bioselective adsorption from crude cell lysates on biotinylated controlled-pore glass and used to catalyze interesterification of anhydrous butteroil. Changes in the triacylglycerol composition indicated that those with equivalent carbon numbers (ECN) ranging from 36 to 42 decreased, while those with ECN values from 48 to 50 increased following interesterification for 120 h in hexane at 42 degrees C. Both the melting temperatures and the solid fat content at various temperatures were lower as compared to those of the unmodified butteroil. Addition of unsaturated fatty acids, linoleic and linolenic, yielded modified butteroils with lower melting points and solid fat content, whereas addition of saturated fatty acids, palmitic and stearic, increased the solid fat content of the modified butteroil. The liquid butteroil could function as a solvent as well as the substrate; however, the interesterification reaction rate was much slower than in hexane.
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