Antioxidant, flavonoid, α-tocopherol, β-carotene, fatty acids, and fermentation profiles of alfalfa silage inoculated with novel Lactiplantibacillus Plantarum and Pediococcus acidilactici strains with high-antioxidant activity

Six lactic acid bacteria strains with high-antioxidant activity were screened and applied to alfalfa silage to develop antioxidant probiotics for silage production. Alfalfa was ensiled without inoculants (control) or with a commercial strain (Lactiplantibacillus plantarum GFG) and antioxidant strains L. plantarum 24-7 (24-7), L. plantarum BX62 (BX62), L. plantarum AS21 (AS21), L. plantarum FM15 (FM15), Pediococcus acidilactici 13-7 (13-7), P. acidilactici J17 (J17) at dry matter concentration of 400 g/kg for 60 d, respectively. Alfalfa silage was investigated on silage fermentation, chemical and microbial compositions, antioxidant enzymes, total flavonoid, α-tocopherol, β-carotene and fatty acid. The results showed that AS21, FM15, 13-7, and J17 inoculations improved (P < 0.001) lactic acid concentration in alfalfa silage compared with control and GFG-treated silages. Compared with control and GFG-treated silages, AS21- (P < 0.001), FM15- (P = 0.007), 13-7- (P = 0.03), and J17-treated (P < 0.001) silages decreased ammonia nitrogen concentration. All inoculants with high-antioxidant activity reduced the losses of α-tocopherol (P < 0.001) and β-carotene (P < 0.001). Higher total flavonoid concentration was found in 24-7- (P = 0.004), BX62- (P < 0.001), FM15- (P = 0.03), J17-treated (P < 0.001) silages versus control. In comparison to control and GFG-treated silages, 24-7- (P < 0.001), BX62- (P < 0.001), AS21- (P = 0.004), FM15- (P = 0.002), J17-treated (P < 0.001) silages had higher proportion of polyunsaturated fatty acid. Except for strain J17, inoculations with the screened strains had higher (P < 0.001) total antioxidant capacity (T-AOC) activity in alfalfa silage compared with control and GFG-treated silages. The highest T-AOC (P < 0.001, 200 U/g FW) was observed in AS21-treated silage. Inoculated silages had higher (P < 0.001) glutathione peroxidase activity versus control. Conversely, compared with control and GFG-treated silages, lower superoxide dismutase activity was observed in FM15- (P < 0.001) and J17-treated (P < 0.001) silages. Lower lipoxygenase (LOX) activity (P < 0.001) was observed in screened strains treated-silages compared with control and GFG-treated silages. Pearson correlation analysis showed that T-AOC was positively correlated with α-tocopherol (r = 0.66, P = 0.05) and β-carotene (r = 0.76, P = 0.02), but negatively correlated with LOX (r = − 0.67, P = 0.05). Conclusively, all the tested strains with high-antioxidant activity can be used as candidate strains to improve the antioxidant status of ensiled alfalfa, and strain AS21 is the most preferred strain.