Submitted to: Proceedings of the ASMS Conference on Mass Spectrometry and Allied Topics
Publication Type: Proceedings
Publication Acceptance Date: May 1, 2004
Publication Date: May 23, 2004
Citation: Nunez, A., Ashby, R.D., Foglia, T.A., Solaiman, D. Characterization of sophorolipids produced by rhodotorula bogoriensis and their lipase-mediated rearrangement products. In: Proceedings of the ASMS Conference on Mass Spectrometry and Allied Topics. May 22-27, 2004, Nashville, Tennessee. 2004 CDROM. Technical Abstract: The yeast Rhodotorula bogoriensis (formerly Candida bogoriensis) was grown in a medium that used glucose and oleic acid as the carbon substrates. The sophorolipids produced were isolated from the medium by extraction with ethyl acetate and subsequently separated and characterized using the above LC/APCI-MS method. The APCI spectra of the products indicated that the sophorose ring contained varying degrees of acetylation at carbon 6' and 6' positions. The sugar ring was glycosylated to a C22:0 fatty acid, but a minor co-product with a C24:0 fatty acid also was identified. The use of oleic acid in the growth media did not influence the final composition of the fatty acid chain-length as has been observed with the sophorolipids produced by C. bombicola. In the APCI/MS spectrum specific fragmentation ions corresponding to the sophorose ring and hydroxy fatty acid structure indicated that the fatty acid was in the free acid form. The presence of the primary alcohols and the carboxylic acid functionality in the molecule was studied as potential reactive centers for the formation of biopolymers through enzymatic esterification. The sophorolipid mixture was hydrolyzed with base to remove the acetyl group and the de-acetylated product was esterified using an immobilized lipase in tetrahydrofuran. The formation of intra-molecular esters (lactones) versus inter-molecular esters (dimers or oligomers) was determined by LC/ESI-MS. The results indicated that lactone formation was the dominant esterification pathway in this lipase-catalyzed reaction.