Abstract
The immobilization of biocatalysts on magnetic nanomaterial surface is a very attractive alternative to achieve enzyme nanoderivatives with highly improved properties. The combination between the careful tailoring of nanocarrier surfaces and the site-specific chemical modification of biomacromolecules is a crucial parameter to finely modulate the catalytic behavior of the biocatalyst. In this work, a useful strategy to immobilize chemically aminated lipase B from Candida antarctica on magnetic iron oxide nanoparticles (IONPs) by covalent multipoint attachment or hydrophobic physical adsorption upon previous tailored engineering of nanocarriers with poly-carboxylic groups (citric acid or succinic anhydride, CALBEDA@CA-NPs and CALBEDA@SA-NPs respectively) or hydrophobic layer (oleic acid, CALBEDA@OA-NPs) is described. After full characterization, the nanocatalysts have been assessed in the enantioselective kinetic resolution of racemic methyl mandelate. Depending on the immobilization strategy, each enzymatic nanoderivative permitted to selectively improve a specific property of the biocatalyst. In general, all the immobilization protocols permitted loading from good to high lipase amount (149 < immobilized lipase < 234 mg/gFe). The hydrophobic CALBEDA@OA-NPs was the most active nanocatalyst, whereas the covalent CALBEDA@CA-NPs and CALBEDA@SA-NPs were revealed to be the most thermostable and also the most enantioselective ones in the kinetic resolution reaction (almost 90% ee R-enantiomer). A strategy to maintain all these properties in long-time storage (up to 1 month) by freeze-drying was also optimized. Therefore, the nanocarrier surface engineering is demonstrated to be a key-parameter in the design and preparation of lipase libraries with enhanced catalytic properties.
Highlights
In recent years, the global population growing and economy improvement in many countries has been leading to an increase of industrial life products with consequent generation of waste responsible of environmental problems and worsening of human life quality [1]
In this study iron oxide nanoparticles (IONPs) were synthesized by co-precipitation method followed by acid treatment to increase their size distribution and crystallinity obtaining NPs with enhanced magnetic properties [39,54]
Uncoated NPs resulted colloidally unstable at pH 7 because their charge was close to zero, as confirmed by ζ-potential measurements (Figure 1)
Summary
The global population growing and economy improvement in many countries has been leading to an increase of industrial life products with consequent generation of waste responsible of environmental problems and worsening of human life quality [1]. Polymers 2018, 10, 615 alternative technologies able to produce a wide set of industrial products while reducing consumption of resources and the impact on the environment is largely growing. To this end, biotechnology—or the use of bio-materials and green production processes—is a well-established reality [2,3]. Enzymatic processes show several advantages with respect to the chemical ones in order to obtain final desired products: mild reaction conditions, simple operational procedures, high productivity, specificity, high regio- and enantioselectivity [3]
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