甘蔗尾青贮中乳酸菌与酵母菌互作机制的研究

Guangxi is the main area for sugarcane production in china. Sugarcane tops are harvested in winter, and can be used as ruminant forage to solve the problem of forage shortage in winter. Ensilage can soften the sugarcane tops and increase its volatile organic acids, which can increase its palatability and animal intake. Our previous results find that the sugarcane silage has lower aerobic stability than corn silage, which may be owing to the yeast ferment the sugar into ethanol during fermentation periods. There is a great practical and theoretical significance for solving low aerobic stability problem if we study the interaction mechanism between lactic acid bacteria and yeast in the sugarcane tops silage. This project will take sugarcane tops as research target, using traditional microbe isolation and modern molecular biotechnologies to detect the changing regulation of dominant species, numbers of lactic acid bacteria and yeast, and screen the dominant lactic acid bacteria. Then we will use the screened lactic acid bacteria to ensilage sugarcane tops, the fermentation indexes and aerobic stability of sugarcane tops silage will be measured. Then, the fermentation indexes data will be evaluated by principal component analysis to get the candidate lactic acid bacteria strains which can produce high content of acetic acid which is an anti-fungal compounds. Finally, based on the results of this project, the candidate lactic acid bacteria strains will be tested again in sugarcane tops silage to elucidate the mechanism of lactic acid bacteria and yeast interaction to improve sugarcane tops silage`s aerobic stability. This project can supply theoretical basis to explore sugarcane tops utilizing additives and promote application of sugarcane in ruminant nutrition.

广西盛产甘蔗，甘蔗尾可部分弥补冬季饲草短缺的问题。甘蔗尾青贮使坚硬的甘蔗叶梢软化，提高动物适口性。我们前期工作发现，与青贮玉米秸秆相比，甘蔗尾青贮的有氧稳定性较差，可能是由于甘蔗尾青贮过程中酵母菌发酵糖类转化为乙醇所致。探讨甘蔗尾青贮中乳酸菌与酵母菌互作机制对解决甘蔗尾青贮难题具有重要的理论和实践意义。本项目以甘蔗尾为研究对象，用传统分离鉴定和现代分子生物学技术相结合的方法动态检测青贮不同阶段优势乳酸菌和酵母菌种类，数量变化规律；筛选优势乳酸菌；再应用筛选到的若干乳酸菌菌株青贮甘蔗尾，测定有机酸、氨态氮、有氧稳定性，通过主成分分析法初步确定乳酸菌与酵母菌互作效应较高的乳酸菌株（即能产生较高浓度可抑制酵母菌生长的乙酸），应用上面获得的乳酸菌对甘蔗尾进行添加青贮研究，阐明乳酸菌与酵母菌如何互作达到改善青贮有氧稳定性的机制。本项目的实施，为甘蔗尾开发利用或研制甘蔗尾专用青贮添加剂提供理论依据。

探讨甘蔗尾青贮中乳酸菌与酵母菌互作机制对解决甘蔗尾青贮有氧稳定性较差的难题具有重要的理论和实践意义。本项目研究了甘蔗梢自然青贮过程中发酵参数及营养成分的动态变化以及甘蔗梢自然青贮过程中营养成份和细菌多样性的变化规律，结果表明，甘蔗梢在自然青贮条件下青贮30d即可达到良好青贮效果，综合营养成分、青贮参数、和微生物多样性分析，60天青贮效果最优，Lactobacillales目中的Lactobacillus属细菌在甘蔗梢自然青贮中占主导地位。此外，本研究还对甘蔗尾自然青贮过程中乳酸菌、酵母菌进行了分离与鉴定，结果表明，甘蔗尾自然青贮过程中发挥作用的主要有20株乳酸菌株和7株酵母菌菌株，乳酸菌包括干酪乳杆菌（Lactobacilluscasei）1株、副干酪乳杆菌（Lactobacillus paracasei）2株、植物乳酸杆菌（Lactobacillus plantarum）17株，酵母菌菌株包括3株矮小假丝酵母（ Candida humilis）、4株酿酒酵母（Kazachstania humilis）。研究了优势乳酸菌与酵母菌互作对甘蔗尾青贮品质的影响，结果表明，添加100%植物乳杆菌的发酵品质最优，但综合抗氧化性、营养成分以及乳酸菌与酵母菌的互作效应分析，以乳杆菌为主、添加适量的酵母菌（植物乳杆菌60%、干酪乳杆菌10%、副干酪乳杆菌10%、矮小假丝酵母菌20%）进行甘蔗尾青贮效果最好。甘蔗尾青贮发酵剂的研制及应用试验结果表明，4种乳酸菌及酵母菌按照植物乳杆菌50-60%、干酪乳杆菌10-20%、副干酪乳杆菌10-20%、矮小假丝酵母菌10-20%的比例配合用于甘蔗尾青贮发酵，均能取得较好的青贮发酵效果及互作效应，并研制出了4个甘蔗尾青贮发酵剂配方。以上结果将有利于制作质量更好、稳定性更高的甘蔗尾青贮发酵饲料。