It is well-known that lysozyme (Ly) is an excellent natural food preservative to prolong the storage and shelf life of a wide range of food products. However, its bioactivity is often compromised when it coexists with negatively charged polysaccharides due to their unfavorable interactions. In this study, we investigated the influence of carboxymethyl cellulose (CMC) on Ly structure and antibacterial activity under the different Ly:CMC mass ratios and thermal treatment. The Ly-CMC complexes were characterized by turbidity, protein intrinsic and isothiocyanate labeled fluorescence, Fourier transform infrared and circular dichroism spectroscopies. The antibacterial activities of Ly were measured via enzyme activity and inhibition zone methods. The results showed that the extent of their interactions could be regulated with Ly:CMC mass ratios. The strongest interactions were found at the mass ratio of 5:1, leading to the significant structural changes and thus the least heating stability of Ly. As a result, the enzyme activity and antibacterial property of Ly were restrained at the maximum level at this mass ratio owing to the strongest screening effects on the active sites, altering spatial structure and neutralizing the surface charges. Notably, further increasing CMC concentration weakened the interactions and decomposed the complex, resulting in the recovery of the bioactivity of Ly until reaching the ratio of 1:1. However, when the mass ratio of Ly:CMC became smaller  than 1:1, the bioactivity of Ly was diminished again due to the steric-hindrance effect of excessive CMC. In addition, heating aggravated such negative effect on the Ly bioactivity. Findings from this work shed some light on the possible explanation of negative effects from polysaccharides on the bioactivity of Ly during food processing.<br/>

Understanding the effects of carboxymethyl cellulose on the antibacterial ability of lysozyme at different mass ratios and thermal treatment

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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