Screening And Identification Of Bacillus’s And Its Effects On Immune And Digestive Function Of Carp

In this study, fifteen strains of Bacillus subtilis were separated from fishpond, and fish intestinal and microbial ecological agents, from which we screened three strains(SYB1-1, RYB1-8 and BYB2-5) of Bacillus subtilis with high enzyme production, strong enzyme activity and bacteriostatic action, identified as Bacillus subtilis, Bacillus licheniformis and Bacillus cereus respectively. Four diets were formulated to contain basic diet(Control), Bacillus subtilis only(Group I), Bacillus subtilis and Bacillus licheniformis(Group II), Bacillus subtilis, Bacillus licheniformis and Bacillus cereus(Group III). Two hundred and forty fishes were randomly divided into 4 groups and fed 4 diets respectively for 45 d to explore the effect of Bacillus on the immunity, antioxidant capacity and intestinal mucosa of carp. The results are showed as follws:(1) Three strains with strong enzyme activity named as were obtained, SYB1-1, RYB1-8 and BYB2-5. enzyme activity of protease, amylase and cellulase of SYB1-1 were 32.14 U, 39.15 U, 17.68 U respectively; enzyme activity of protease, amylase and cellulase of.RYB1-8 were 27.69 U, 28.25 U, 15.56 U respectively; enzyme activity of protease, amylase and cellulase of BYB2-5 were 22.80 U, 25.10 U, 14.67 U respectively. Four strains with bacteriostatic action were obtained. SYB1-1, RYB1-8 and BYB2-5 had an strong inhibition effect on bacteria and the ratio of bacteriostatic ring/bacteria circle in diameter was 1.2, 1.09 and 1.15. Twelve strains of Bacillus had a inhibitory effect on Staphylococcus aureus, in which SYB1-1, RYB1-8 and BYB2-5 had a stronger effects with, the ratio of bacteriostatic ring/bacteria circle in diameter(2.52, 2.34 and 2.24) Based on the morphological, physiological and biochemical characteristics and 16 S r DNA sequencing, SYB1-1, RYB1-8, BYB2-5 were classified as Bacillus subtilis, Bacillus licheniformis and Bacillus cereus respectively.(2) Compared to the control group, the percentage of phagocytic in group II was significantly increased by 20.2%(P<0.05), the phagocytic index by 41.5%(P<0.05), Immunoglobulin M(Ig M) by 26.1%(P<0.05), lysozyme activity in group II was increased by 21.9%(P<0.05), the content of intestinal mucosal secretory immunoglobulin A(SIg A) by 53%(P<0.05) in serum, and transformation rate of lymphocyte by 32%(P<0.05).Meanwhile, the content of SIg A in group I was significantly increased by 92%(P<0.05).(3) In group II, the activity of hepatopancreas total superoxide dismutase(T-SOD) was significantly increased by 69.4%(P<0.05), carpand glutathione peroxidase(GSH-PX) was significantly increased by 25.4%(P<0.05), catalase(CAT) was significantly increased by 76.4%(P<0.05), total antioxidant capacity(T-AOC) was significantly increased by 69.4%(P<0.05), whereas malondialdehyde(MDA) content was significantly decreased by 28.9%(P<0.05),glutathione(GSH) activity up to 35.6%(P<0.05) compared to the control group.(4) Compared to the control group, the height of intestinal mucosal folds by 25.13%(P<0.05), intestinal mucosa layer thickness by 11.83%(P<0.05),and intestinal microvilli by 43.48%(P<0.05).The results indicated that three strains(SYB1-1, RYB1-8 and BYB2-5) of Bacillus subtilis were successfully isolated and identified. The different combination of bacillus improved the immunity, antioxidant capacity and intestinal mucosa of carp, especially the combination of Bacillus subtilis and Bacillus licheniformis.