Mihaela D. Leonida

Fairleigh Dickinson University, USA

Title: Tannic Acid as Modulator of Nisin Release from Composites with Antibacterial Activity

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Biography

Dr. Mihaela Leonida received a MS and a Ph.D. in Chemical Engineering from the Polytechnic University in Bucharest, Romania and a Ph.D. in Bioorganic Chemistry from Wesleyan University in Middletown, CT, USA. At the present, she teaches biochemistry at Fairleigh Dickinson University in Teaneck, NJ, USA. Dr. Leonida’s research interests are in the field of redox enzyme stabilization and bionanomaterials with biological activity. She is the author of several books and over 70 papers published in science journals and conference proceedings.

Abstract

Nisin, a bacteriocin, is a natural preservative used in the food industry. Among its shortcomings leakage in lipophilic environments is an important one. We encapsulated nisin in a marine biopolymer in order to improve is release profile. Composite materials were prepared using a mild, environmentally friendly procedure, ionotropic gelation of chitosan by sodium tripolyphosphate in the presence of nisin (N) at different concentrations. In two parallel sets of preparations, tannic acid (TA) was added at 10:1 and 5:1 N:TA, respectively. The obtained particles were characterized by FTIR, SEM, size, zeta potential, encapsulation efficiency, loading capacity, and ratio of residual free amino groups. The kinetics of nisin release from the particles was studied to assess the role of TA as a potential modulator thereof. Its presence resulted in enhanced release, higher at lower N:TA ratio. An additional benefit was that TA, a strong antioxidant, imparted antioxidant activity to the composites. Antimicrobial turbidimetric tests were performed against one gram-positive bacterium (Staphylococcus aureus) and two gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), all relevant for the food, pharmaceutical, and cosmetic industries. All the composites showed synergistic effects against all the bacteria tested. The positive coaction was stronger against the gram-negative species. This is remarkable since nisin itself has notrac known activity against them.