3.6. Antimicrobial activity
The antimicrobial activity of carrageenan and carrageenan-based
nanocomposite films was investigated using agar well diffusion method
using food-borne pathogens such as E. coli and L. monocytogenes. The
results of the antimicrobial activities determined by the diameter of inhibition
zone (DI) of the film samples are shown in Fig. 6. As expected, the neat carrageenan film didn't show any inhibitory activity against
both Gram-positive (L. monocytogenes) (DI = 5 mm) and Gramnegative
(E. coli) bacteria (DI = 5 mm), however, the composite films
included with AgNPs or clay mineral exhibited clear antibacterial activity
against both pathogens. The AgNP-included nanocomposite films
showed pronounced antimicrobial activity against Gram-negative bacteria
(DI = 7.96 mm) with slight antimicrobial activity against Gram-positive
bacteria (DI = 5.76 mm). On the contrary, the clay-included
nanocomposite film showed distinctive antimicrobial activity against
Gram-positive bacteria (DI=6.26mm) with slight antimicrobial activity
against Gram-negative bacteria (DI=5.21mm).