Screening Of Lactic Acid Bacteria Community At Low Temperature And Its Application In Dry Cornstalk For The Micro Storage

Straw feed is the component of ruminant animals, which can relieve the contradictions between people and animals for food and the problem of forage shortage. In Northeast China, the roughage for ruminant animals is in shortage, while the low temperature of this region after autumn restricts the fermentation of straw feed. The high contention of lignocelluloses, low nutritional value and palatability of dry yellow straw have become the limitation of its large-scale usage. To raise the utilization ratio of dry yellow straw feed and expand the using range, it is particularly important to develop a more efficient and stable lactic acid bacteria community and simplify the feed technology of straw at low temperature.To solve the problem of dry yellow corn straw which can’t be micro-storaged under the condition of low temperature.We obtained a lactic acid bacteria community named LAC-1 at low temperature derived from the silage by the method of continuous restricted cultivation. It was proved efficient, stable and can decrease pH rapidly during fermentation.The single factor experiment and response surface method were used to optimize the best culture conditions of community LAC-1. The strains diversity of community LAC-1 was analyzed by the dilution plate method and 16S rDNA molecular cloning technology. Moisture content, temperature and inoculation quantity were used as single factor respectively to optimize the best culture conditions of the cornstalk fermentation system. The community of LAC-1 was inoculated to the dry cornstalk fermentation system, whose moisture content was 60-70%, to evaluate the quality of the fermented feed by the research of the sensory quality, pH, WSC, proteins, organic acids, NDF, and ADF changes. The micro organisms’quantity of dynamic change of lactic acid bacteria, acetobacter rancens bacteria, mould, yeast and other microorganisms were also studied. Sheep feeding experiment was used to study the feeding effect by observing the quantity of feed intake and body weight changes of the sheep. The results are as follows:1、The optimal culture parameters of LAC-1 were:culture temperature 9.5℃, inoculated quantity 3.3%, culture time 139 h. The pH of culture solution was reduced to 4.0 under this condition.2、By the method of infinite dilution separation, we get three pure culture strains:LAC1-a, LACl-b, and LAC1-c, they are Lactobacillus nodensis、Lactobacillus curvatus、Lactobacillus sakei respectictively. They all belonged to the homofermentative fermentation, which carbon source were saccharides and the production were acetic and lactic acid.16S rDNA sequence determination and molecular clone technology analysis showed that the community of LAC-1 was mainly composed by Lactobacillus.nodensis Lactobacillus:curvatus、Lactobacillus.sakei,Lactobacillus.kimchii、Lactobacillus.delbrueckii subsp. bulgaricus strain、Lactobacillus.letivazi and Lactobacillus.tucceti. They all belonged to Lactobacillus and produce bacteriocin inhibit miscellaneous bacterial growth. At the same time, the LAC1-a, LAC1-b, and LAC1-c are corresponding to clones LAC1-1、LAC1-2 and LAC1-3.3、Compared with control, the pH, Dry Matter, Water-Soluble Carbohydrates, and the number of mold and yeast of the inoculation treatment decreased significantly after three days, with a significant rise in crude protein, lactic acid, acetic and the number of lactic acid bacteria, but the number of acetobacter rancens bacteria in fermentation decreased significantly after five days.4、The changes of fermentation system in microbial diversity:At initial fermentation, enterobacteriaceae is the advantage bacterium in the fermentation system by 61.8%, followed by pseudomonas, rhizobia, uncultivate the bacteroidetes, etc. At the end of fermentation, enterobacteriaceae are still advantage bacterium in control treatment by 65.5%, followed by Pseudomonadaceae, Lactobacillus, Uncultured bacterium; In the treatment of LAC-1 of straw fermentation system, Lactobacillus in the proportion of 82.5%, followed by enterobacteriaceae which is 17.5%.5、The feeding of test results are as follows:The palatability improved significantly after micro storage effects of cornstalk. For the experimental group, the sheep of feed intake increased by 32.8%. The weight of sheep in the treatment group is 1.3 times of control in trial period. The single sheep increased economic benefit is 17.2yuan for economic benefit.After inoculating LAC-1 in the dry cornstalk, it could effectively colonize into the straw fermentation system, improve its quality and accelerate the fermentation process. Compared with the control, the feeding sheep weight and silage intake increased significantly.