Martina Pinto

Influence of the Morphology of Core-Shell Supports on the Immobilization of Lipase B from Candida antarctica

Core-shell polymer particles with different properties were produced through combined suspension-emulsion polymerizations and employed as supports for immobilization of lipase B from Candida antarctica. In order to evaluate how the morphology of the particles affects the immobilization parameters, empirical models were developed to describe the performance of the biocatalysts as a function of the specific area, volume of pores and average pore diameter of the supports. It was observed that the average pore sizes did not affect the enzymatic activities in the analyzed range of pore sizes. It was also observed that the increase of the specific area (and of the volume of pores) led to higher enzyme loadings, also leading to an increase in the esterification activity, as expected. However, when the specific area (and volume of pores) increased, the hydrolytic activity and the retention of hydrolytic activity of the biocatalysts decreased, indicating the existence of diffusional limitations for some hydrolytic reactions, probably because of the high reaction rates.

Design of a core–shell support to improve lipase features by immobilization

Different core–shell polymeric supports, exhibiting different morphologies and composition, were produced through simultaneous suspension and emulsion polymerization, using styrene (S) and divinylbenzene (DVB) as co-monomers. Supports composed of polystyrene in both the core and the shell (PS/PS) and the new poly(styrene-co-divinylbenzene) support (PS-co-DVB/PS-co-DVB) were used for the immobilization of three different lipases (from Rhizomucor miehie (RML), from Themomyces lanuginosus (TLL) and the form B from Candida antarctica, (CALB)) and of the phospholipase Lecitase Ultra (LU). The features of the new biocatalysts were evaluated and compared to the properties of commercial biocatalysts (Novozym 435 (CALB), Lipozyme RM IM and Lipozyme TL IM) and biocatalysts prepared by enzyme immobilization onto commercial octyl-agarose, a support reported as very suitable for lipase immobilization. It was shown that protein loading and stability of the biocatalysts prepared with the core–shell supports were higher than the ones obtained with commercial octyl-agarose or the commercial lipase preparations. Besides, it was shown that the biocatalysts prepared with the core–shell supports also presented higher activities than commercial biocatalysts when employing different substrates, encouraging the use of the produced core–shell supports for immobilization of lipases and the development of new applications.

Evaluation of the performance of differently immobilized recombinant lipase B from Candida antarctica preparations for the synthesis of pharmacological derivatives in organic media

This paper shows the production of lipase B from Candida antarctica (LIPB) after cloning the gene that encoded it in Pichia pastoris using PGK as a constitutive promoter. The production of the lipase is lower using this strategy but it avoids the use of inducers like methanol. The performance of this enzyme was compared with that of the commercial enzyme (CALB) after immobilization on different supports in different reactions. As supports, we used Accurel 1000, and three core–shell supports (poly(methyl methacrylate) on the core and on the shell – PMMA/PMMA; poly(methyl methacrylate-co-divinylbenzene) on the core and on the shell – PMMA-co-DVB/PMMA-co-DVB; and poly(styrene-co-divinylbenzene) on the core and on the shell – PS-co-DVB/PS-co-DVB). The popular Novozym 435 was also utilized to assess the features of the new biocatalysts. All these supports adsorbed lipases via interfacial activation of the open form of the lipase on the hydrophobic surface of the supports. The studied reactions were esterification of oleic acid and ethanol in a solvent-free medium, resolution of (±)-1,3,5-O-benzyl-myo-inositol via acylation using vinyl acetate in hexane and resolution of (±)-1,2-O-isopropylidene-3,6-di-O-benzyl-myo-inositol via acylation using vinyl acetate (solvent free system). The results varied depending on the employed supports and on the studied reactions, but some general trends may be observed, pointing to better behavior of LIPB compared to CALB. The use of 4 different supports gave more strength to these differences, as it did not depend on a specific difference between a single support/enzyme pair, but it is more general. Thus, LIPB seems to have some advantages compared to the commercial enzyme on all the reactions assayed in this paper. PS-co-DVB/PS-co-DVB-LIPB is in general the most active preparation (even 50% higher activity was observed). Further investigations are in development to determine the structural reasons for these differences.

Control of Polymerization Processes

Automation and advanced control of polymerization reactors constitute problems of paramount importance in the polymerization field, given the inherent complexity of most polymerization processes, allowing for safer and more stable operations, higher process productivities, and more secure environmental performance of these processes. For this reason, the present article provides an overview regarding the main subjects discussed in the literature of polymerization control. Particularly, this study highlights some classical polymerization control problems, describing some of the techniques available to monitor and control polymerization reactions and presenting some examples in each field.