柳枝稷青贮用乳酸菌复合系的组成多样性及其代谢特性

Composition diversity and metabolic characters of lactic acid bacteria community SGL

摘要:

摘要:【目的】筛选一组乳酸产量高、组成稳定的柳枝稷青贮用乳酸菌复合系。【方法】通过连续限制性培养方法获得乳酸菌复合系SGL，使用变性梯度凝胶电泳(DGGE)和高通量测序技术分别分析其群落结构的稳定性和组成多样性。在培养基中添加不同氮源，测定氮源对SGL菌体生长和代谢产酸的影响。【结果】连续限制性培养8代，SGL的菌群结构趋于稳定，主要菌种为同型发酵乳酸菌，包括Lactobacillus nantensis (78.78%)、Lactobacillus plantarum(7.92%)、Lactobacillus pantheris(5.27%)、Bacillus coagulans(4.41%)和Lactococcus lactics(3.31%)，是现有唯一的同时包含Lactobacillus、Lactococcus和Bacillus的乳酸菌复合系。酵母浸粉是促进SGL菌体生长和产乳酸的最好氮源，最适添加量为20 g/L。当(NH4)2SO4和酵母浸粉中N的比例为1:4时，菌体生长量和乳酸产量与20 g/L 酵母浸粉等同。【结论】乳酸菌复合系SGL 多样性高、组成稳定、可利用无机氮源，作为青贮饲料添加剂，具有很大的应用潜力，本研究为SGL的培养和应用提供了理论依据。

Abstract:

Abstract:［Objective］We aimed to select a stable lactic acid bacteria community from switchgrass silage，that was efficient in lactic acid production.［Methods］We obtained the community by continuous restricted subcultivation in MRS broth，and analysed the composition diversity and stability of the community by 16S rRNA gene-based pyrosequencing and Denaturing Gradient Gel Electrophoresis (DGGE)，respectively．In addition，we studied the effect of different nitrogen sources on growth and lactic acid production of the community，through adding different concentrations of yeast extraction，different nitrogen sources［yeast extract，peptone，urea and (NH4)2SO4］and different proportions of (NH4 )2SO4 and yeast extract leveled with elemental nitrogen 1.8 g/L.［Results］The microbial composition of SGL became stable from the 8th generation according to the results of DGGE．The pH value of the MRS inoculated with SGL dropped to 3.7，and the concentration of lactic acid reached 26 g/L after 24 h cultivation．The result of the pyrosequencing showed that the major composition of SGL were Lactobacillus nantensis (78.78%)，Lactobacillus plantarum (7.92%)，Lactobacillus pantheris (5.27%)，Bacillus coagulans (4.41%) and Lactococcus lactics (3.31%)．The best supplementation of yeast extraction for SGL was 20 g/L．When the elemental nitrogen ratio of (NH4)2SO4 to yeast extract was 1:4，the growth and lactic acid production were no significant difference with 0:5 (P＜0.05).［Conclusion］SGL had a great potential of application，as an efficient inoculant for ensilage or lactic acid production． This study would offer theoretical basis for cultivate and application of SGL in production.