Abstract: Aiming at a silage inoculant that could quickly debase and stabilize the pH value of fresh grass, and add to it more L(+) lactic acid, a continuous restricted cultivation of the material was carried on until three groupsof microbial community-Li6, A12-, Ru2-have been selected from fermented forage, a lfalfa silage and a lactic bacteria agent. The three groups of microbial community alignith the target: debasing the pH value quickly and inducing the silage to emit a sugary fragrance. Uultured in corn medium, alfalfa medium, and MRS,the three groups of microbial community cause the mediums’pH value to debase to 3.8~4.0 within 10 hours, 16 hours, and 20 hours respectively. Through GC-MS analysis, large amount of metabolic products such as lactic acid and acetic acid, and some formic acid and propionic acid are obtained. Other materials like butanediol, ethyl acetate, acetaldehyde, glycerol are also produced. Among the metabolic products,lactic acid and acetic acid take 98% of the total, in which 60%~70% is L(+) lactic acid.

Key words: Grassland science, Alfalfa, Silage, Microbial community, Selection, Fermenting characteristic

摘要： 以pH值的降低迅速、稳定,L(+)乳酸积累量多为指标,通过连续的限制性培养,从发酵饲料、青贮苜蓿及乳酸菌制剂中分别筛选出Li6、Al2和Ru2三组菌系,以期作为苜蓿青贮用菌剂。该三组菌系均pH下降迅速,发出香甜气味,在玉米粉培养基、苜蓿汁培养基、MRS培养基中将pH稳定到3.8～4.0之间,所需时间分别为10h、16h和20h。气质联机分析结果表明,发酵液中含有较高的乙酸、乳酸,还有少量甲酸、丙酸等挥发性脂肪酸及丁二醇、乙酸乙酯、异丁醛、乙醛和乙酰胺等风味物质;在代谢产物中乙酸和乳酸占总代谢物的98%以上,其中L(+)乳酸的比率高达60%～70%。

关键词: 草原学, 苜蓿, 青贮, 菌系, 筛选, 发酵特性