Mucor miehei stability

The stability of the ester surfactants against enzymatic hydrolysis by two different microbial Upases, Mucor miehei lipase (MML) and Candida antarc-tica lipase B (CALB) added separately to the surfactant solutions, was also investigated, see Fig. 5 [19]. It is obvious that hydrolysis of the unsubstituted surfactant is much faster with both CALB and MML than that of the substituted surfactants, i.e., increased steric hindrance near the ester bond leads to decreased hydrolysis rate. Since the specificity of the enzyme against its substrate is determined by the structure of the active site, it can be concluded, as expected, that the straight chain surfactant most easily fits into the active site of both enzymes. 

The chemical stability of the amide bond is high. When the surfactant containing an amide bond was subjected to 1 M sodium hydroxide during five days at room temperature, only 5% of the amide surfactant was cleaved. The corresponding experiment performed in 1 M HCl resulted in no hydrolysis. The amide bond was, however, found to be slowly hydrolyzed when lipase from Candida antarctica or peptidase was used as catalyst. Amidase and lipase from Mucor miehei was found to be ineffective. Despite the very high chemical stability, the amide surfactant biodegrades by a similar path in the... 

Lipases (E.C. 3.1.1.3.) catalyze the hydrolysis of lipids at an oil/water interface. In a membrane reactor, the enzymes were immobilized both on the side of the water phase of a hydrophobic membrane as well as on the side of the organic phase of a hydrophilic membrane. In both cases, no other means for stabilization of the emulsion at the membrane were required. The synthesis reaction to n-butyl oleate was achieved with lipase from Mucor miehei, which had been immobilized at the wall of a hollow fiber module. The degree of conversion reached 88%, but the substrate butanol decomposed the membrane before the enzyme was deactivated. 

The three dimensional structures of human pancreatic Lipase and Rhizo-mucor miehei lipase have recently been elucidated 1141-1431. Among the lipases purified foam different sources—mammals, bacteria, fungi, and plants-—the fungal lipases from Rhizopuj species exhibit a remarkably broad pH zone of stability and activity, extending from pH 3 to 9. 

After immobilization, one can also notice a shift toward higher optimum temperatures. As immobilization provides a rigid external backbone for the lipase molecules, the effect of higher temperatures in breaking the interactions that are responsible for the catalytically active structure becomes less prominent, and so temperature optimum is expected to increase. Immobilization also affixes the enzyme in one conformation, which reduces the susceptibility of the enzyme to denamration by heat. Immobilized lipases, such as those from Mucor miehei and Candida antarctica (34), show good thermal stability at temperatures required to process most fats and oils and are therefore most appropriate for the biomodification of fats and oils. 

Delimitsou, C., Zoumpanioti, M., Xenakis, A., Stamatis, H. 2002. Activity and stability studies of mucor miehei lipase immobilized in novel microemulsion-based organogels. Biocatal. Biotransf 20, 319-327. 

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