This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives. This includes their use to activate supports and ...immobilize enzymes
via
ion exchange, as well as to improve immobilized enzymes by coating with PEI. PEI is a polymer containing primary, secondary and tertiary amino groups, having a strong anion exchange capacity under a broad range of conditions, and the capability to chemically react with different moieties on either an enzyme or a support. Also, as a multifunctional polymer, it has been modified stepwise to introduce different functionalities into the same polymer. This polymer (in combination with other anionic ones) permits the generation of "saline" environments around enzyme molecules, improving enzyme stability in the presence of hydrophobic compounds. The use of PEI as a physical glue useful to crosslink enzyme subunits in multimeric enzymes, monomeric enzymes immobilized
via
physical interactions or production of enzyme multilayers will be specially emphasized as new open avenues for enzyme coimmobilization. The coimmobilization of enzymes and cofactors using PEI may become one of the future developments allowed through an adequate use of this polymer and new pathways towards the design of enzyme combi-catalysts for their use in cascade reactions. Some unexplored but suggested uses derived from the properties of PEI are also proposed in the review, like the use of the buffering power of this multifunctional polymer to avoid pH gradients inside biocatalyst particles. Thus, although PEI has been a largely popular polymer in biocatalyst design, it looks like a long and in some cases almost unexplored road lies ahead.
This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives.
Lipases are the most widely used enzymes in biocatalysis, and the most utilized method for enzyme immobilization is using hydrophobic supports at low ionic strength. This method allows the one step ...immobilization, purification, stabilization, and hyperactivation of lipases, and that is the main cause of their popularity. This review focuses on these lipase immobilization supports. First, the advantages of these supports for lipase immobilization will be presented and the likeliest immobilization mechanism (interfacial activation on the support surface) will be revised. Then, its main shortcoming will be discussed: enzyme desorption under certain conditions (such as high temperature, presence of cosolvents or detergent molecules). Methods to overcome this problem include physical or chemical crosslinking of the immobilized enzyme molecules or using heterofunctional supports. Thus, supports containing hydrophobic acyl chain plus epoxy, glutaraldehyde, ionic, vinylsulfone or glyoxyl groups have been designed. This prevents enzyme desorption and improved enzyme stability, but it may have some limitations, that will be discussed and some additional solutions will be proposed (e.g., chemical amination of the enzyme to have a full covalent enzyme-support reaction). These immobilized lipases may be subject to unfolding and refolding strategies to reactivate inactivated enzymes. Finally, these biocatalysts have been used in new strategies for enzyme coimmobilization, where the most stable enzyme could be reutilized after desorption of the least stable one after its inactivation.
•Lipases immobilization on hydrophobic supports via interfacial activation is described in this review•This protocol permits the one step immobilization, purification, stabilization and hyperactivation of lipases•Lipases may be released from the support under certain conditions•Intermolecular crosslinking may prevent enzyme release•Heterofunctional supports prevent enzyme release but they have some limitations•There are many ways of taking full advantage of the new heterofunctional supports
Enzymatic biocatalysis is a sustainable technology. Enzymes are versatile and highly efficient biocatalysts, and have been widely employed due to their biodegradable nature. However, because the ...three-dimensional structure of these enzymes is predominantly maintained by weaker non-covalent interactions, external conditions, such as temperature and pH variations, as well as the presence of chemical compounds, can modify or even neutralize their biological activity. The enablement of this category of processes is the result of the several advances in the areas of molecular biology and biotechnology achieved over the past two decades. In this scenario, metal–organic frameworks (MOFs) are highlighted as efficient supports for enzyme immobilization. They can be used to ‘house’ a specific enzyme, providing it with protection from environmental influences. This review discusses MOFs as structures; emphasizes their synthesis strategies, properties, and applications; explores the existing methods of using immobilization processes of various enzymes; and lists their possible chemical modifications and combinations with other compounds to formulate the ideal supports for a given application.
Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes. It is based on immobilization
via
interfacial activation of lipase B from
Candida antarctica
on a resin, ...Lewatit VP OC 1600. This resin is a macroporous support formed by poly(methyl methacrylate) crosslinked with divinylbenzene. N435 is perhaps the most widely used commercial biocatalyst in both academy and industry. Here, we review some of the success stories of N435 (in chemistry, energy and lipid manipulation), but we focus on some of the problems that the use of this biocatalyst may generate. Some of these problems are just based on the mechanism of immobilization (interfacial activation) that may facilitate enzyme desorption under certain conditions. Other problems are specific to the support: mechanical fragility, moderate hydrophilicity that permits the accumulation of hydrophilic compounds (
e.g.
, water or glycerin) and the most critical one, support dissolution in some organic media. Finally, some solutions (N435 coating with silicone, enzyme physical or chemical crosslinking, and use of alternative supports) are proposed. However, the N435 history, even with these problems, may continue in the coming future due to its very good properties if some simpler alternative biocatalysts are not developed.
Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.
In this communication, lipase A from
(CALA) was immobilized by covalent bonding on magnetic nanoparticles coated with chitosan and activated with glutaraldehyde, labelled CALA-MNP, (immobilization ...parameters: 84.1% ± 1.0 for immobilization yield and 208.0 ± 3.0 U/g ± 1.1 for derivative activity). CALA-MNP biocatalyst was characterized by X-ray Powder Diffraction (XRPD), Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetry (TG) and Scanning Electron Microscope (SEM), proving the incorporation of magnetite and the immobilization of CALA in the chitosan matrix. Besides, the immobilized biocatalyst showed a half-life 8-11 times higher than that of the soluble enzyme at pH 5-9. CALA showed the highest activity at pH 7, while CALA-MNP presented the highest activity at pH 10. The immobilized enzyme was more active than the free enzyme at all studied pH values, except pH 7.
Enzymes serve as biocatalysts for innumerable important reactions, however, their application has limitations, which can in many cases be overcome by using appropriate immobilization strategies. ...Here, a new support for immobilizing enzymes is proposed. This hybrid organic-inorganic support is composed of chitosan-a natural, nontoxic, biodegradable, and edible biopolymer-and sodium polyphosphate as the inorganic component. Lipase B from
(CALB) was immobilized on microspheres by encapsulation using these polymers. The characterization of the composites (by infrared spectroscopy, thermogravimetric analysis, and confocal Raman microscopy) confirmed the hybrid nature of the support, whose external part consisted of polyphosphate and core was composed of chitosan. The immobilized enzyme had the following advantages: possibility of enzyme reuse, easy biocatalyst recovery, increased resistance to variations in temperature (activity declined from 60 °C and the enzyme was inactivated at 80 °C), and increased catalytic activity in the transesterification reactions. The encapsulated enzymes were utilized as biocatalysts for transesterification reactions to produce the compound responsible for the aroma of jasmine.
The synthesis of ethyl butyrate catalyzed by lipases A (CALA) or B (CALB) from
immobilized onto magnetic nanoparticles (MNP), CALA-MNP and CALB-MNP, respectively, is hereby reported. MNPs were ...prepared by co-precipitation, functionalized with 3-aminopropyltriethoxysilane, activated with glutaraldehyde, and then used as support to immobilize either CALA or CALB (immobilization yield: 100 ± 1.2% and 57.6 ± 3.8%; biocatalysts activities: 198.3 ± 2.7 U
/g and 52.9 ± 1.7 U
/g for CALA-MNP and CALB-MNP, respectively). X-ray diffraction and Raman spectroscopy analysis indicated the production of a magnetic nanomaterial with a diameter of 13.0 nm, whereas Fourier-transform infrared spectroscopy indicated functionalization, activation and enzyme immobilization. To determine the optimum conditions for the synthesis, a four-variable Central Composite Design (CCD) (biocatalyst content, molar ratio, temperature and time) was performed. Under optimized conditions (1:1, 45 °C and 6 h), it was possible to achieve 99.2 ± 0.3% of conversion for CALA-MNP (10 mg) and 97.5 ± 0.8% for CALB-MNP (12.5 mg), which retained approximately 80% of their activity after 10 consecutive cycles of esterification. Under ultrasonic irradiation, similar conversions were achieved but at 4 h of incubation, demonstrating the efficiency of ultrasound technology in the enzymatic synthesis of esters.
The aim of this paper was to evaluate different strategies of chitosan activation using cross-linking reagent like glycidol, epichlorohydrin, and glutaraldehyde for
Thermomyces lanuginosus
lipase ...(TLL) immobilization. Operational activity and stability by esterification of oleic acid with ethanol and thermal inactivation using these derivatives were investigated. Derivative obtained by sequentially activation with glycidol, ethylenediamine, and glutaraldehyde and subsequent TLL immobilization showed the best performance, with high hydrolytic activity value. Its stability was 15-fold higher than solubilized TLL in the evaluated inactivation conditions (60 °C, 25 mM sodium phosphate buffer pH 7). After 5 cycles of oleic acid esterification, only a few percentage of its conversion has reduced. On the other hand, glycidol-activated chitosan derivative showed very low hydrolytic activity value. Epichlorohydrin-activated chitosan derivative showed regular hydrolytic activity value. Both derivatives showed low immobilization yields. Operational stability of this last derivative was very low, where after the first cycle of oleic acid esterification, only 56% of its initial conversion was obtained.
Graphical Abstract
In this work, the combination of different lipases was employed for the production of biodiesel, using the Free Fatty Acids (FFAs) from Residual Chicken Oil (RCO) as a substrate. As biocatalysts, ...lipases A and B from
Candida antarctica
(CALA and CALB, respectively) and lipase from
Rhizomucor miehei
(RML) were used in different combinations; as a result, the best lipase cocktail was composed of 67% CALB and 33% RML, which was used to optimize the esterification reaction parameters (molar ratio (FFAs/ ethyl alcohol), biocatalyst content, temperature and time) by the Taguchi method. Under optimized conditions (1:5, 15% of lipase cocktail, 30 °C and 3 h), it was possible to achieve 89.95 ± 0.3% of conversion.
Graphic Abstract
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