Selection And Characteristics Of Probiotics From Intestinal Tract Of Ictalurus Punctatus

The series consequences of antibiotics abuse cause panic in the society. To find a safe and nontoxic replacer is imperative. Probiotics is just the good choice. This paper focuses on selection of probiotics from bacterial strains which were isolated from intestinal tract of cultured healthy Ictalurus punctatus, 342 bacterial strains were used for testing the antagonistic against commonly five strains of pathogenic bacteria of cultured Ictalurus punctatus and protease, amylase, lipase, gelatinase production, also we discussed the enhancement of immune response in Ictalurus punctatus were inoculated with formalin killed Aeromonas hydrophila and were fed with feed supplemented with appropriate amount of yeast immunopolysacchride.The main results and conclusions summarized as:(1) Studies of the intestinal microflora is a prerequisite for the development of probiotics. Amount and constitute of aerobic and facultive anaerobic bacterial flora in intestinal tract of cultured healthy Ictalurus punctatus were detected. The results showed that the number of the foregut, midgut and hindgut is 1.3×l0⁶cfu/g, 1.6×10⁶ cfu/g and 4.6×10⁶cfu/g. Enterobacter cloacae, Vibrio fluvialis , Plesiomonas shigelloides, Stenotrophomonas maltophilia, Escherichia coli, Vibrio alginolyticus, Bacillus subtilus, Shewanella putrefaciens, Aeromonas salmonicida masoucida, Chryseobacterium indologenes, Raoultella planticola, Acinetobacter baumannii, Burkholderia cepacia, Aeromonas hydrophila, Micrococcus, Brucella, Aerornonas, Bacillus, Corynebacte rium, Vibriop and Erwinia were detected.(2) Aerobic and facultive anaerobic bacterial flora from intestinal tract of cultured healthy Ictalurus punctatus and Ictalurus punctatus suffering from enteric scepticemia were compared. The results showed that the total intestinal microflora in Ictalurus punctatus suffering from enteric scepticemia was less than which in healthy Ictalurus punctatus, the species of bacterial flora and the ratio of each bacterial flora also had significant differences. Eight species of bacterial flora were detected in intestinal tract of cultured healthy Ictalurus punctatus, while four species of bacterial flora were detected in Ictalurus punctatus suffering from enteric scepticemia. The ratio of Aeromonas, Enterobacteriacea, Vibrion, Bacillus, Acinetobacter, Micrococcus, Corynebacterium, Pseudomonas and other bacterial flora in healthy Ictalurus punctatus was 46.7%, 26.4%, 13.3%, 2.9%, 1.9%, 1%, 1%, 1% and 5.7%, respectively. The ratio of Aeromonas, Vibrion, Enterobacteriacea, Corynebacterium and bacterial flora in Ictalurus punctatus suffering from enteric scepticemia was 67.3%, 16.3%, 10.2%, 1.0% and 5.1%, respectively. (3) 342 bacterial strains of intestinal tract of cultured healthy Ictalurus punctatus were used for selecting probiotics, The results showed that 59 strains were able to produce extra-cellular amylase, 62 strains excrete protease, 57 strains excrete lipase, 76 strains excrete gelatinase, and 6 strains antagonistic against commonly pathogenic bacteria among them. The strains BH0142,BH0124,BHI344 were selected as candidates, but The strains BH0142 has tolerance to 8 kinds antibiotics in common, The strains BH0142 was pathogenic bacteria for aquatic. From all of test items, the strains BHI344 were suitable as probiotics Ictalurus punctatus. The strains BHI344 are identified by 15 biochemical and physicological reactions, and fall into Bacillus subtilus.(4) In order to choose a perfect culture medium with different ingredients, after a series of comparative tests, and the result was that: The optimum temperature, time, inoculum sizes and initial pH was 35℃, 16h, 5ï¼…(v/v) and 7.6, respectively, beef extract, glucose and CaCl₂ in the optimum seed culture medium is 2.0ï¼…(w/v), 1.5ï¼…(w/v) and 0.3ï¼…(w/v), and the microbe number of BHI344 could reach 2.62×10⁹cfu/ml after 16hours' fermentation.