Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

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The interesterification yield (IY) and changes in fatty acid positional distribution of selected butter fat triacylglycerols were investigated, using a wide range of commercial microbial lipases and organic solvent media. The interesterification of butter fat by lipase from Mucor miehei was carried out in hexane, hexane-chloroform, and hexane-ethyl acetate; the results showed that the addition of 30% of either chloroform or ethyl acetate to the hexane resulted in a 23% increase in the IY. The interesterification of butter fat in a microemulsion co-surfactant system, containing Brij 35 as surfactant and 1-heptanol as co-surfactant, resulted in an increase in the triacylglycerols that contain C18:0 at sn-2 position, located originally at sn-1,3 positions, with a concomitant interchange with C14:0 and C18:1 at the same position. The interesterification of butter fat by lipase from Rhizopus niveus, in a phosphatidylcholine reverse micellar system, showed an increase in C16:0 at the sn-2 position, with a concomitant decrease in the proportion of small chain fatty acids (C4-C10:0); however, the interesterification of butter fat in co-surfactant free microemulsion systems, containing hexane and ionic (phosphatidylcholine) and non-ionic (sorbitol monostearate and polyoxyethylene sorbitan monostearate) surfactants, showed that the interesterified selected triacylglycerols were enriched with C18:0 and C18:1, originally located on sn-1,3 position, at sn-2 position with concomitant interchange with C12:0, C14:0 and C16:0, originally located at the same position. The interesterification of butter fats, in co-surfactant free microemulsion system, by four microbial lipases showed that those catalyzed by lipase from R. niveus demonstrated a 46% increase in the proportion of C18:1 at sn-2 position whereas those catalyzed by enzymes from M. javanicus, R. delemar and M. miehei were enriched with C16:0 at the same position, by 21%, 35% and 41%, respectively. In addition, lipase from

The screening, biomass production of lipase-producing microorganisms from several sources, as well as the purification, characterization and utilization of the enzymatic extracts for the interesterification of butter fat were investigated. Pseudomonas fragi CRDA 323 and Aspergillus niger CBS 131.52 were considered to be good lipase producers, whereas, those from Pseudomonas putida ATCC 795 and Rhizopus oryzae ATCC 34612 as weak ones; all four microorganisms produced maximal amount of extracellular lipases by batch fermentation after three-four days of incubation in a continuously stirred tank reactor. The lipases were partially purified by ammonium sulfate precipitation and characterized with respect to pH, kinetic parameters and molecular size. The lipases from P. fragi and P. putida were optimal at pH 8.5 and 8.0, respectively, whereas those from A. niger and R. oryzae were optimal at pH 7.5. The A. niger lipase had the lowest V$ sb{max}$ value $ rm(0.51 times 10 sp3 U min sp{-1});$ R. oryzae the highest $ rm (1.86 times 10 sp3 U min sp{-1}).$ The K$ sb{m}$ values for P. fragi, P. putida, A. niger and R. oryzae lipases were 0.70, 1.18, 0.97 and 0.98 mg ml$ sp{-1},$ respectively. Interesterification of butter fat by the partially purified enzymatic extracts in a microemulsion free co-surfactant system containing sorbitol monostearate and polyoxyethylene sorbitan monostearate in the ratio 48:52 (V/V) decreased the water activity as well as the hydrolytic activity. The P. fragi lipase had the highest interesterification yield value (43%) and the R. oryzae lipase the lowest (4%). In addition, P. fragi lipase exhibited the highest decrease (18%) in long-chain hypercholesterolemic fatty acids (C12:0, C14:0 and C16:0) at the sn-2-position; the P. putida lipase demonstrated the least favorable changes in specificity at the same position. Continuous cultivation technique was developed to investigate the screening for lipase-producing microorganisms from four commercial

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). "December 2007." Includes bibliographical references (leaves 130-134). Also available via the World Wide Web.

M.Sc. (Biochemistry) / Please refer to full text to view abstract

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Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 101-116). Also available on the World Wide Web.

Thesis (Ph.D.)--McMaster University, 2003. / Advisor: Gerard D. Wright. Also available via World Wide Web.