Antioxidant, flavonoid, ?-tocopherol, 0-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, alpha-tocopherol, 0-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 alpha-tocopherol (P < 0.001) and 0-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 alpha-tocopherol (r = 0.66, P = 0.05) and beta-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.

Automated summary

This study screened lactic acid bacteria strains with high-antioxidant activity and applied them to alfalfa silage. The results showed that these strains improved fermentation, reduced ammonia nitrogen concentration, decreased the loss of antioxidants, and increased total antioxidant capacity and polyunsaturated fatty acid content. Among them, strain AS21 exhibited the best performance.