Evaluation of ε-polylysine as antimicrobial alternative for liquid-stored boar semen

epsilon-polylysine (epsilon-PL) has potent antibacterial effects and is often used in the food industry. However, nostudies have clarified the antibacterial effects of epsilon-PL during storage of boar semen. In this study, boar semen samples were diluted with BTS buffer supplemented with different concentrations (0, 0.04, 0.08, 0.16, 0.32, 0.64, and 1.28 g/L) of epsilon-PL and different combinations of epsilon-PL plus gentamicin during liquid storage at 17 degrees C for 5 days. Bacterial concentrations, bacterial community compositions, sperm quality parameters, and in vitro fertilization (IVF) were evaluated in order to analyze the antibacterial effects of these parameters during boar semen preservation. The results indicated that the optimum concentration of epsilon-PL was 0.16 g/L, which significantly improved sperm quality parameters, including sperm motility, plasma membrane integrity, mitochondrial membrane potential, and acrosome integrity, and changed bacterial proliferation and composition (P<0.05). Moreover, compared with the control group, IVF parameters in the treatment groups also significantly improved (P<0.05), although there were no significant differences among treatment groups. Interestingly, the antibacterial effect of 0.16 g/L epsilon-PL in combination with 0.125 gentamycin was similar to that of 0.25 g/L gentamicin alone. In conclusion, our results showed that 0.16 g/L epsilon-PL is promising for the replacement of gentamicin to improve sperm quality parameters, sperm capacitation, and IVF by reducing bacterial concentrations and disrupting bacterial community composition. (C) 2019 Published by Elsevier Inc.