The Screening And Mixed Culture Of Probiotics For Breeding

Microbial feeding additives is a new green feeding additives.have the advantages of natural, no pollution, no toxic effect and some other characteristics attracting people’s favor. It can cover the shortage of antibiotics, also play a special function on active agent. Above all, adding probiotics in to feeding additive has important practical significance on the development and increase of the animal husbandry’s economic situation. In order to screen the strains with the ability of produceing cellulases, proteinase and glucoamylase from the soil of chiken farm, we get optimum medium formula from useing DPS data processing software to do uniform experiments. Using optimum medium to culture the mixed bacteria,we could optimize the mixed culture condition. Finally, we compared the ability of enzyme production with mixed culture.Seven strains which can produce cellulases, proteinase and glucoamylase were screened from the soil of chiken farm. There are5strains have higher producing ability of enzyme which named X4, X5, X7, Fi, F4. The repetitive screening results showed that the X4, X5, F4were able to tolerate6%NaCl, and they did not produce H2S, H2O2. In addition, they could inhibit the growth of E. col. But, X7produced viscous substance and F1produced H2O2when cultured for24hours at30℃. Consequently, we decided that the X4, X5, F4were the strains which we were wanted. To bacteria density at OD650for index, we found cultur X4, X5and F4with the proportion of X4:X5:F4=2:1:1.That was the best proportion.The culture medium of mixed bacteria was respectively optimum by the uniform design. Using DPS data processing software for training results of linear regression analysis.The optimum medium formula was obtained that was glucose20g/L, peptone22g/L, beef extract23g/L, soluble starch13g/L. Mixed bacteria in the optimum medium culturing for18hours at30℃.Using plate counting method to calculate the effective viable counts of bacteria can reach1.06×108cfu/mL.Optimizing the conditions of mixed culture (culture time, initial pH value, culture temperature, inoculation amount) by using orthogonal test. The results show that mixed bacterial growth better in the conditions of inoculation amount3%, initial pH7.5, culturing12hours at35℃. The effective viable counts of bacteria can reach1.58×109cfu/mL. The viable counts of bacteria were increased by14.9times with the prior medium formula.Using the enzyme activity as the index, compared with the enzyme activity changes of the mixed bacteria in different fermentation temperature, initial pH and different fermentation time.The results show that cellulases, proteinase and glucoamylase activity can along with the fermentation temperature and fermentation time increased, but the glucoamylase enzyme in fermented60hours enzyme activity decreased; protease in the initial pH8enzyme activity is higher, glucoamylase enzyme activity decrease when the initial pH increases, in the conditions of initial pH7.5, cellulose actinity is higher.