Mesoporous enzyme entrapment

In this communication a study of the catalytic behavior of the immobilized Rhizomucor miehei lipase in the transesterification reaction to biodiesel production has been reported. The main drawbacks associated to the current biodiesel production by basic homogeneous catalysis could be overcome by using immobilized lipases. Immobilization by adsorption and entrapment have been used as methods to prepare the heterogeneous biocatalyst. Zeolites and related materials have been used as inorganic lipase supports. To promote the enzyme adsorption, the surface of the supports have been functionalized by synthesis procedures or by post-treatments. While, the enzyme entrapping procedure has been carried out by sol-gel method in order to obtain the biocatalyst protected by a mesoporous matrix and to reduce its leaching after several catalytic uses. 

The large size of the pores of MCM-41 has also allowed the entrapment of enzymes, such as cytochrome c, papain and trypsin [193]. Enzyme entrapment has been extensively performed with sol-gel materials. The types of applications of redox catalysis using enzyme-mesoporous materials is expected to parallel the sol-gel materials, which is discussed in the last section of this chapter. 

Cosnier, S., Senillou, A., Gratzel, M., et al. (1999) A glucose biosensor based on enzyme entrapment within polypyrrole films electrodeposited on mesoporous titanium dioxide. J. 

Figure 1). Finally, high ordered pure silica mesoporous material, containing lipase enzyme by entrapping procedure, has been obtained by sol-gel method (XRD results not showed).

In fact, after 5 reaction cycles the entrapped lipase shows a residual activity of the 60%, with respect to the total leaching that occurs after 3 or 2 reaction cycles for the adsorbed enzyme (Figure 2). Moreover, with respect to the biodiesel total productivity of the free lipase, the entrapped RML shows, after 5 reaction cycles, a value that is almost 6 times higher (1.62 mg FAME /mg Enz h and 0.28 mg FAME /mg Enz h, respectively for entrapped and free lipase). Concerning the stability of the inorganic matrix that covers the enzyme, after tested reaction cycles (five), mesoporous structure remains unaltered an stable (Figure 3). This indicates that the lipase leaching is due to the enzyme release and not to the collapse of matrix. 

Fig. 19 Entrapment of enzymes into mesoporous silica sphere covered with LbL films of polyelectrolyte and silica nanoparticle...

Improved activity upon immobilization in mesoporous silicates was also observed by electrochemical studies. It was demonstrated that the specific activity of organophosphorus hydrolase entrapped in mesoporous amine functionalized ordered-silicate powder could reach more than twice as high as that of the free enzyme, and in a subsequent article it was reported that enzymatic sensor for paraoxon based on the immobilization of enzyme-grafted mesoporous silicate particulates in Nation film was reported [334]. 

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