The Isolation Of Nitrogen-Fixing Bacteria And Cellulose Degrading Bacteria And The Effect Of The Two Microbes On In Vitro Fermentation

The purpose of this experiment was to isolate and identify facultative anaerobic nitrogen-fixing bacteria (NFB) and cellulose degrading bacteria (CDB) from the rumen of Holstein cows, and study the effect of mixed culturing the two kinds of bacteria on in vitro fermentation, in order to obtain the best combination of NFB and CDB which could promoted cellulose degradation and utilization to provide a theoretical basis for production practice in the bacteria used as a feed additiveThe isolation and identification of facultative anaerobic NFB and CDB from the rumen:three Holstein cows (three and half years old dry period) with permanent rumen fistula were used to provide rumen fluid. Medium separation for the two types of bacteria was studied, and the predominant strains were gotten by physiological and biochemical experiments. The result showed that21of CDB and23of NFB were isolated from rumen fluid of cows and they were all facultative anaerobic bacteria.9of CDB and7of NFB dominant bacteria were screened out by Congo red medium and acetylene reduction test.The effect of CDB and NFB ratios to decomposite the cellulose:predominant strains from the above were cultured in the total volume of2×108CFU.The proportion of CDB and NFB was4:1,3:2,2:3, and1:0. The best combination ratio of the two kinds of microbes was obtained through items of the enzyme activity, pH changes and other indicators. The results showed that6combination of three CDB (A, B, C) and two NFB (D, E) were gotten with better resolution capabilities of fibrous and a more stable pH range. The best ratio of CDB and NFB was4:1.The effect of adding different kinds of NFB and CDB on rumen fermentation was investigated in vitro batch cultures of rumen fluid from cows. The experiment set12groups, the inoculum concentration of single or mixed (the mixing ratio was4:1) CDB (numbered A, B and C) and NFB (numbered D and E) in each treatment was4X109CFU·L-1. Each treatment was repeated for three times. Values of pH, NH3-N, gas production, bacterial protein content, VFA and dry matter degradation rate and other indicators were measured at2,4,8,12and24h. The results showed that mixture of CDB and NFB could increase the degradation rate of feed and bacterial protein content, lower NH3-N concentration, and gentle medium of pH. Through comprehensive consideration of each index the combination of CDB-B and NFB-D had better effects on fomentation. In summary, the combination of CDB and NFB can be mutually reinforcing and interaction comparing with single addition of CDB. In the test of in vitro, adding mixed strains with the role of promotion rumen fermentation that can help ruminant make better use of fiber feed. If this result can be applied to actual production, will be able to improve feed digestion and utilization, reduce feed costs, and expand the scope of the use of feed ingredients. This will has a good role in the development of animal husbandry.