Characterization of antimicrobial peptides produced by Lactobacillus acidophilus LA-5 and Bifidobacterium lactis BB-12 and their inhibitory effect against foodborne pathogens
Saber Amiri, Reza Rezaei Mokarram, Mahmoud Sowti Khiabani, Mahmoud Rezazadeh Bari, Mohammad Alizadeh
Abstract
This study aimed to optimize the production of antimicrobial peptides (AMPs) by pure and mixed cultures of Lactobacillus acidophilus LA-5 and Bifidobacterium lactis BB-12 in milk model media and then characterize the properties of produced AMPs. The optimal conditions for AMPs bio-production by L. acidophilus LA-5, B. lactis BB-12, and their mixed culture were temperatures of 38.71, 42.00, and 39.00 °C, fermentation times of 26.15 h, 60.00 h, and 36.00 h, and yeast extract concentrations of 4.45%, 6.00%, and 5.00% in cheese whey. At optimal conditions, the inhibition activities of AMPs against L. monocytogenes were 14.03 ± 0.68 mm, 13.33 ± 0.81 mm, and 11.02 ± 1.04 mm by L. acidophilus LA-5, B. lactis BB-12, and their mixed culture, respectively. The SDS-page analysis indicated that L. acidophilus LA-5 and B. lactis BB-12 produced AMPs with two and three fractions, respectively. The Fourier-transform infrared spectroscopy and nuclear magnetic resonance tests showed the typical characteristics of a peptide for produced AMPs. The DSC test indicated that produced AMPs had high-temperature stability. These AMPs were bioactive in a wide range of pH (3–9) and temperature (40–100 °C for 30 min). The results of minimum inhibitory concentration and minimum bactericidal concentration showed that the AMPs had antimicrobial effects against important food-borne pathogens.