AUTHOR=Zheng Meixia , Zhang Chong , Zhou Ying , Lu Zhaoxin , Zhao Haizen , Bie Xiaomei , Lu Fengxia 

TITLE=Preparation of Gallic Acid-Grafted Chitosan Using Recombinant Bacterial Laccase and Its Application in Chilled Meat Preservation

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01729

DOI=10.3389/fmicb.2018.01729

ISSN=1664-302X

ABSTRACT=<p>To improve the antibacterial and antioxidant properties of chitosan (CS), CS grafted with gallic acid (GA) using recombinant bacterial laccase from <italic>Bacillus vallismortis</italic> fmb-103 (fmb-rL103) as a catalyst. The structures of grafted chitosans were identified using Fourier transform infrared spectroscopy (FT-IR) and UV visible spectrum (UV–Vis spectroscopy). After gallic acid grafting, the antibacterial properties of chitosans against <italic>Pseudomonas</italic>, <italic>Acinetobacter</italic>, <italic>Brochothrix thermosphacta</italic>, <italic>Escherichia coli</italic>, <italic>Staphylococcus aureus</italic>, <italic>Salmonella</italic>, and <italic>Listeria monocytogenes</italic> were significantly improved. Meanwhile, 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging results showed that the antioxidant properties of grafted CS increased as well. The preservative effects of the grafted chitosan on chilled meat were then investigated. For this purpose, the quality indexes of the chilled meat during the storage were monitored, including total bacterial count, total basic volatile nitrogen (TVB-N) content, pH value, color and thiobarbituric acid reactive substances (TBARS) and so on. The results showed that coating with the grafted chitosan retarded the growth of spoilage bacteria, and decreased TVB-N and TBARS values of meat. The shelf life of chilled meat coated by CS grafted with GA (GA-g-CS) also extended from 6 days to 18 days at 4°C. These results provided a theoretical basis for the future application of the GA-g-CS in the preservation of chilled meat.</p><p><bold>Highlights:</bold><list list-type="simple" prefix-word="simple"><list-item><label>(1)</label><p>The temperature and pH-stable bacterial laccase was used to synthesize gallic acid grafted chitosan.</p></list-item><list-item><label>(2)</label><p>Antioxidant and antibacterial properties of chitosan were improved through grafting gallic acid.</p></list-item><list-item><label>(3)</label><p>Storage properties of chilled meat were improved by coating with gallic acid grafted chitosan.</p></list-item></list></p>