Abstract
Zeolitic imidazolate framework-8 (ZIF-8) is widely used as a protective coating to encapsulate proteins via biomimetic mineralization. The formation of nucleation centers and further biocomposite crystal growth is entirely governed by the pure electrostatic interactions between the protein’s surface and the positively charged Zn(II) metal ions. It was previously shown that enhancing these electrostatic interactions by a chemical modification of surface amino acid residues can lead to a rapid biocomposite crystal formation. However, a chemical modification of carbohydrate components by periodate oxidation for glycoproteins can serve as an alternative strategy. In the present study, an industrially important enzyme glucose oxidase (GOx) was selected as a model system. Periodate oxidation of GOx by 2.5 mM sodium periodate increased negative charge on the enzyme molecule, from −10.2 to −36.9 mV, as shown by zeta potential measurements and native PAGE electrophoresis. Biomineralization experiments with oxidized GOx resulted in higher specific activity, effectiveness factor, and higher thermostability of the ZIF-8 biocomposites. Periodate oxidation of carbohydrate components for glycoproteins can serve as a facile and general method for facilitating the biomimetic mineralization of other industrially relevant glycoproteins.
Highlights
According to MarketsandMarketsTM Company Research, the global enzyme market is projected to grow from USD 5.9 billion in 2020 to USD 8.7 billion in the six years, owing to a global need for sustainability, higher process efficiency, and green, environmentally friendly technology and industry [1]
Thermostability of soluble proteins, biocomposites washed with water, and biocomposites washed with 10% w/v Sodium dodecyl sulfate (SDS) was determined by incubation in water at 65 ◦C for 1 h and specific activity measurement afterwards, as described above
Many of the industrially important enzymes belong to the group of glycoproteins, a chemical modification of carbohydrate components can serve as an alternative strategy
Summary
According to MarketsandMarketsTM Company Research, the global enzyme market is projected to grow from USD 5.9 billion in 2020 to USD 8.7 billion in the six years, owing to a global need for sustainability, higher process efficiency, and green, environmentally friendly technology and industry [1]. The common shortcomings of this strategy include the high price of ligands’ components and the low yield of the obtained enzyme@MOF composites Encapsulation is another useful immobilization technique where a biocomposite (termed enzyme@MOF) is formed by the direct mixing of the MOF components (i.e., metal ions and ligands) in the presence of the enzyme. Several parameters influence the formation, structure, and activity of the enzyme@MOF composites, especially those obtained from ZIF-8 building units by the biomimetic mineralization process. A recent study, where a chemical modification of surface amino acid residues of various proteins was done, points out that the enhancement of these electrostatic interactions by the chemical functionalization of a protein surface, making it more negative, leads to a rapid biocomposite crystal formation This method is proposed as a general strategy for facilitating biomimetic mineralization [18]. This study may provide a blueprint for how to tailor the surface chemistry of glycoproteins and anticipates that such a facile one-pot enzyme immobilization strategy will open new avenues in developing industrially important biocomposite catalysts with superior catalytic properties
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