A new, mild cross-linking methodology to prepare cross-linked enzyme aggregates

Area of Science:

• Biocatalysis and Enzyme Engineering
• Protein Immobilization Techniques
• Industrial Biotechnology

Background:

• Cross-linked enzyme aggregates (CLEAs) are a widely used form of enzyme immobilization.
• Traditional cross-linking agents like glutaraldehyde can lead to significant loss of enzyme activity.
• Development of novel cross-linking strategies is crucial for improving enzyme immobilization efficiency.

Purpose of the Study:

• To evaluate dextran polyaldehyde as a cross-linking agent for preparing CLEAs.
• To compare the immobilization efficiency and activity of CLEAs prepared using dextran polyaldehyde versus glutaraldehyde.
• To investigate the impact of the cross-linker size on enzyme active site accessibility and retention.

Main Methods:

• Preparation of CLEAs from penicillin G acylase, hydroxynitrile lyase, alcohol dehydrogenase, and nitrilases.
• Enzyme immobilization via precipitation followed by cross-linking with dextran polyaldehyde or glutaraldehyde.
• Active site titration to quantify the number of active enzyme sites in the prepared CLEAs.

Main Results:

• Dextran polyaldehyde generally yielded higher immobilization efficiencies compared to glutaraldehyde.
• CLEAs prepared with dextran polyaldehyde exhibited significantly higher enzyme activity.
• Active site titration revealed a lower loss of active sites when using dextran polyaldehyde, suggesting reduced interaction with catalytic residues.

Conclusions:

• Dextran polyaldehyde is an effective and potentially superior cross-linking agent for CLEA preparation.
• The larger molecular size of dextran polyaldehyde likely prevents it from accessing and reacting with enzyme active sites.
• This approach offers a promising strategy for enhanced enzyme immobilization, preserving catalytic activity for biotechnological applications.