Enzyme-assisted process for DAG synthesis in edible oils.

This study deals with the enzymatic synthesis of diacylglycerols in rapeseed oil by the esterification of free fatty acids and monoacylglycerols. As enzymatic reactions are influenced by many factors, a statistical design of experiments was conducted to investigate the enrichment of diacylglycerols, systematically. Simultaneously, the investigated method contributes to the refining process, as the amount of free fatty acids could be reduced significantly from 2% to 0.3%. Utilizing an immobilized lipase from Rhizomucormiehei, a maximum diacylglycerol content of 23% was obtained, after optimization. By washing with iso-propanol and hexane the immobilised lipase could be reused in 14 consecutive batches. In addition, glycerol was proven to be an alternative to MAG as acyl-group acceptor. However, the diacylglycerol enrichment was not accomplished in the same yields as for monoacylglycerols. Summarizing, the present study revealed the potential of an enzymatic diacylglycerol synthesis in edible oils as a suitable alternative to conventional processes also enabling the reduction of free fatty acids in crude oils.

Enzymatic esterification of free fatty acids in vegetable oils utilizing different immobilized lipases.

Different immobilized lipases were screened for their ability to esterify free fatty acids (FFA) with monoacylglycerol (MAG) as acyl-group acceptor. A lipase from Rhizomucor miehei (Lipozyme RMIM) was the most suitable for lipase-catalyzed de-acidification-a promising alternative to conventional neutralization. A reduction of the FFA content to 0.6 % (w/w) was achieved by applying a substrate with an initial FFA-content of 6 % (w/w), the reaction at 50 °C for 22 h as well as the stepwise addition of a quadruple stoichiometric amount of MAG.

Differential expression of tissue inhibitor of matrix metalloproteinases 3 in uveal melanoma.

Based on gene profiling, two entities of uveal melanomas exist. So far, these two entities can be distinguished by the chromosome 3 status which strongly associates with the metastatic potential of the tumours. Reorganization of the extracellular matrix is one of the steps towards dissemination of tumour cells. In the present study, we examined the tissue inhibitor of matrix metalloproteinases (TIMP) 3 expression in 19 uveal melanomas and compared the results with histopathological and genetic features. The expression level of TIMP-3 mRNA as determined by microarray analysis was associated with the chromosome 3 status of the tumour (p = 0.003). All tumours with disomy 3 showed moderate to high expression of TIMP-3 mRNA, whereas TIMP-3 was highly expressed in one tumour, less expressed in 3 tumours and absent in the remaining 6 tumours with monosomy 3. Immunohistochemistry for TIMP-3 was positive in 9/19 tumours, but only in 3 tumours were more than 5% of the tumour cells stained positive. There was no association between immunohistochemical detection of TIMP-3 and chromosome 3 status. In tumours with disomy 3, we found none or very few TIMP-3-positive cells though the mRNA level was high which indirectly postulates posttranscriptional problems in protein biosynthesis in this entity of uveal melanomas. There was a trend between TIMP-3 protein expression and both cell type (p = 0.11) and presence of loops and/or networks (p = 0.06) in tumour which may indicate a role of TIMP-3 in the biology of uveal melanoma.