青藏高原乳酸菌对垂穗披碱草青贮饲料发酵品质的影响

Effect of lactic acid bacteria isolated from Tibetan Plateau on silage fermentation quality of Elms nutans

【目的】为了探究青藏高原乳酸菌对垂穗披碱草发酵品质的影响。【方法】本试验将3株从青藏高原垂穗披碱草(Elymus nutans Griseb.)中筛选的耐低温乳酸菌(戊糖片球菌PP-6,植物乳杆菌LP-2和清酒乳杆菌LS-5)作为添加剂加入垂穗披碱草进行青贮,同时对其生理生化特性进行研究,并以低海拔条件下分离得到的相同菌种的商品化乳酸菌制剂为对照,研究所筛选的3株优良乳酸菌在低温(15℃)和常温条件(25℃)下对垂穗披碱草青贮饲料发酵品质的影响。【结果】试验结果表明,在碳源利用方面,分离得到的戊糖片球菌PP-6(Pediococcus pentosaceus)发酵棉子糖、乳糖、山梨醇、蜜二糖和蔗糖,清酒乳杆菌LS-5(lactobacillus sakei)可发酵棉子糖、苦杏仁苷、鼠李糖、乳糖、山梨醇、木糖、阿拉伯糖、蜜二糖和蔗糖,而相同菌种的商品菌均不能利用,表明高原乳酸菌具有更广泛的糖源利用特性。将筛选得到的3株低温生长优良菌株进行青藏高原垂穗披碱草青贮发酵试验,青贮50 d后,与对照的商品菌处理相比,在15℃时,清酒乳杆菌LS-5显著降低了青贮饲料p H值、丙酸含量和氨态氮/全氮值(P<0.05),且能够保存更多的水溶性碳水化合物和粗蛋白;植物乳杆菌LP-2(lactobacillus plantarum)和戊糖片球菌PP-6作为复合添加剂显著提高了青贮饲料乳酸含量(P<0.05),显著降低了氨态氮/全氮值和中性洗涤纤维含量(P<0.05),能够保存更多的粗蛋白。但在25℃时,此3株菌与对照菌种相比均无明显优势。【结论】上述结果表明,从青藏高原分离筛选的3株菌种在低温条件下可有效提高青藏高原垂穗披碱草青贮饲料的发酵品质。

[Objective] In order to detect the effect of lactic acid bacteria isolated from Tibetan Plateau on silage fermentation quality of Elms nutans. [Methods] We used 3 isolated lactic acid bacteria with better growth at low temperatures of 10 and 15 ℃ at ensiling of Elymus nutans. Subsequently,effects of the selected lactic acid bacteria on fermentation profiles of Elymus nutans silages stored at 15 and 25 ℃ were evaluated by using the same species of commercial inoculants as the control. [Results]PP-6 isolated from Tibetan Plateau could ferment raffinose,lactose,sorbitol,melibiose and sucrose,and LS-5 could ferment cottonseed sugar,laetrile,rhamnose,lactose,sorbitol,xylose,arabinose,melibiose and sucrose,but the same species of commercial strains could not use these sugars. Inoculation of these three strains into Elymus nutans at 15 and 25 ℃ ensiled for 50 d,we found that LS-5 significantly reduced silage p H,propionic acid concentration and ratio of ammonia nitrogen / total nitrogen at 15 ℃（ P〈0. 05）,salvaged more water-soluble carbohydrate and crude protein; Application of LP-2 and PP-6 as a combined inoculant to Elymus nutans significantly improved lactic acid concentration（ P 〈0. 05）,resulting in a lower ratio of ammonia nitrogen / total nitrogen,saved more crude protein and significantly reduced neutral detergent fiber content（ P〈0. 05） as compared with the commercial strains. [Conclusion]The three isolated strains can improve silage quality of Elymus nutans growing on the Qinghai-Tibetan Plateau at low temperature,but these strains have no obvious advantages at 25 ℃ in comparison with the commercial inoculants.