Abstract
Different commercial preparations from Candida rugosa lipase lead often to an irreproducible behaviour when employed in slightly hydrated media, even when different samples from the same supplier are used. This conduct is triggered by several causes, such as the different concentration of the "real" catalyst in the different crude samples (quantity), or the inherent problems related to heterogeneous biocatalysts (i. e., different amount of water, diffusional problems, etc); furthermore, for C. rugosa lipase, the diverse percentage of different isoenzymes (quality) is another irreproducibility-inducing factor. In this sense, for a rational understanding of all the experimental data described for this complex biocatalyst, topics like the description of the role of the inducer on the fermentation, the biochemical characterisation of the crude biocatalysts and the establishment of synthetical strategies to overcome the irreproducibility problems must be covered. Once these tasks are fulfilled, we will be able to understand the relative catalytic activity of different samples from different origins, showing that enzymes should not merely be considered as a "white magic powder" with synthetical utility. Different techniques to evaluate the importance of the amount of water are discussed: 1HNMR for comparing the hydrolytic activity of isoenzymes, and sorption isotherms and Thermogravimetric and Differential Thermal Analysis (TGA/DTA) for understanding the esterification in organic media. Furthermore, different characterisation reactions useful for quantifying the lipase loading (heptyl oleate synthesis and transesterification of vinyl acetate with 1-heptanol) are proposed. Finally, a synthetical strategy based on the acylation, via vinyl acetate, of 1- heptanol, geraniol, nerol and cyclohexanol, for comparing the catalytical results and the isoenzymatic profile is discussed.
Keywords: Rhizomucor Miehei Lipase, Heptyl Oleate Synthesis, Transesterification, alkoxycarbonylation, thermogravimetric analysis (TGA)
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Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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