Abstract:

[Objective] The purpose of this study was to screen the candidate lactic acid bacterial strains for preparing forage silage, so as to improve the fermentation quality of forage silage. [Method] Lactic acid bacterial strains were isolated from the leaves of 8 varieties of gramineous forages, including Pennisetum sinese, Eleusine indica, Imperata cylindrica and so on. On the basis of traditional microbiological identification techniques, molecular biological identification methods and 16S rDNA sequence diversity analysis were used to identify the suspected lactic acid bacterial strains isolated. The performance in growth, acid production and salt tolerance of the lactic acid bacterial strains was characterized. Their growth tolerance under pH value of 3.0, 3.5 and 4.0, as well as NaCl concentrations of 0.02, 0.04, 0.06, 0.08 and 0.10 mg/mL was assessed. Furthermore, their inhibitory effects against Candida, Staphylococcus aureus and Salmonella typhimurium were evaluated. [Result] A total of 30 suspected lactic acid bacterial strains were isolated from the surface of forage leaves. Following phenotypic identification and molecular biological identification, 10 strains of lactic acid bacteria were identified as belonging to the genera of Weissella, Pediococcus and Levilactobacillus, including 3 strains of L. brevis, 2 strains of P. pentosaceus, 2 strains of L. plantarum, 1 strain of W. cibaria, 1 strain of L. pentosus and 1 strain of L. coryniformis. The performance in growth rate and acid production varied among different strains. There were strain-specific salt and acid resistance as well as antibacterial property as well. By comprehensively comparing the biological characteristics of the 10 strains, L. plantarum Lab7 had better performance in salt and acid resistance, while L. brevis Lab1 and L. coryniformis Lab10 had good performance in growth rate, acid production ability, salt and acid resistance, and antibacterial property. [Conclusion] The naturally isolated lactic acid bacterial strains of forage origin, L. plantarum Lab7, L. brevis Lab1 and L. coryniformis Lab10 were screened as candidate strains for lactic acid bacterial preparation used in fermentation of forage silage, and had the potential for further development.

Key words: forage leaf surface, lactic acid bacteria, isolation, identification, biological characteristic