Study on Antibacterial Activity and Structure of Chemically Modified Lysozyme

Area of Science:

• Biochemistry
• Protein modification
• Antimicrobial agents

Background:

• Lysozyme exhibits bacteriostatic properties but has limited efficacy against Gram-negative bacteria.
• Egg white lysozyme is a cost-effective and stable source for modification.
• Expanding lysozyme's antimicrobial spectrum is crucial for its application as a natural preservative.

Purpose of the Study:

• To chemically modify egg white lysozyme using organic acids.
• To evaluate the antibacterial properties of modified lysozyme against Gram-negative and Gram-positive bacteria.
• To investigate the structural changes in lysozyme post-modification and correlate them with altered antibacterial activity.

Main Methods:

• Chemical modification of egg white lysozyme using caffeic acid and p-coumaric acid.
• Utilized 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agents.
• Assessed antibacterial activity via minimum inhibitory concentration (MIC) assays.
• Analyzed structural changes using infrared spectroscopy (amide-I band).

Main Results:

• Modified lysozymes showed decreased activity against Gram-positive bacteria (MIC: 1.25 mg/mL for S. aureus, B. subtilis).
• Enhanced inhibition against Gram-negative bacteria (E. coli, P. aeruginosa) with MICs of 0.5 mg/mL and 0.75 mg/mL for caffeic acid and p-coumaric acid modified enzymes, respectively.
• Infrared spectroscopy indicated alterations in the secondary structure of modified lysozymes compared to the native enzyme.

Conclusions:

• Organic acid modification successfully broadened lysozyme's antimicrobial spectrum, particularly against Gram-negative bacteria.
• Structural modifications are responsible for the altered antibacterial efficacy.
• This approach offers a novel strategy for developing enhanced lysozyme-based preservatives.