Study On Digestive Enzyme-producing Bacteria In The Intestinal Tract Of Ctenopharyngodon Idellus And Carassius Auratus Gibelio

We took the grass carp(Ctenopharyngodon idellus) and silver prussian carp (Carassius auratus gibelio) as the experimental materials and focused on the bacteras which could pruduce digestive enzymes and a group of such bacterias(Bacillus sp.) from the digestive duct of grass carp were isolated.Then we characterized the effects of the bacterias as food additive on the constitution of bacteria community and the activity of proteinase in intestines and hepatopancreas.In our experiments,to study the enzyme-producing bacteria from the digestive tract of grass carp and silver prussian carp,180 strains of bacteria were isolated from the intestinal tract of grass carp and silver prussian carp and the capacity to produce four extracellular enzymes including protease,lipase,amylase and cellulase of all bacteria strains was measured.The results indicated that the dominant group identified were Aeromonas from four digestive enzyme-producing bacteria groups Aeromonas,Vibrio, Bacillus and Pseudomonas isolated from two kind of fish.And of all strains from the gut of C.idellus,45.71%of Aeromonas strains can produce digestive enzyme,in the gut of C.idellus,33 strains could produce four extracellular enzymes,which accounted for 36.67%of the total bacterial populations.From the gut of C.auratus gibelio,43 digestive enzymes-producing strains were isolated,which accounted for 47.78%.The distribution of these clones were shown significant difference aomong foregut,midgut and hindgut of C.idellus while the number of bactetia strains positive(20strains) was markedly higher than that of the rest two part(6 strains in forgut,7 strains in hindgut),coprising 20%, 66.67%and 23.33%in ratio respectively.But in the gut of C.auratus gibelio,the difference of the number of digestive enzymes-producing strains between midgut and hindgut was not obvious,while the number of the positive strains in the foregut was lower compared to that of the midgut and hindgut.There were no cellulase-producing strains in the gut of C.auratus gibelio.So the intestinal bacterias of the fish producing extracellular enzymes have a beneficial effect in the digestive processes of fish.In the test to study the effect of Bacillus Ch9 on the changes of the structer of the intestinal microflora of grass carp,the concentrations of Bacillus Ch9 in four groups were 1.0×10⁹cfu/kg(bacteria concentration/feeding weight )(group F₁),3.0×10⁹ cfu/kg (group F₃),5.0×10⁹cfu/kg(group F₅) and 0 cfu/kg(group F₀) respectively.In our feeding cycle of 56 days,we assayed the species and the number of anaerobic,aerobic and pluralistic groups.The results showed as following:(1) After feeding Bacillus with Ch9, the numbers of the whole intestinal microflora of grass carp were all 10⁶-10⁷cfu/g;the differences was not much evident among the groups;(2) After feeding with Bacillus Ch9, the percentage of Aeromonas and Enterobacteriaceae declined and Bacillus increased as the feeding amount and feeding days inceasing.And the total numbers of anaerobe, Bifidobacterium and Lactobacillus increased after feeding with Bacillus Ch9.However, the change of Bacteriodes's number was not significantly if addition of Bacillus Ch9 or not.In the test to study the effects of Bacillus Ch9 as food additive on the activity of proteinases in different part of intestinal tract and hepatopancreas of grass carp,we designed a gradient of concentrations of Ch9.The grass carps with initial average weight being about 50g were fed with 1.0×10⁹cfu/kg(bacterias conscentration/feeding weight)(group F₁),3.0×10⁹ cfu/kg(group F₃),5.0×10⁹cfu/kg(group F₅) and 0 cfu/kg (group F₀) Bacillus Ch9 respectively.The effect on activity of proteinase,amylase and lipase in different part of intestinal tract and hepatopancreas ware studied.The result showed that the Bacillus Ch9 in a short term(14-28d) could enhance the activity of the proteinase,amylase,lipase both in intestinal tract(foregut,midgut,hindgut) and hepatopancreas,but the activities of there enzymes couldn't further increase but still higher than initial levels after long time feeding(42d-56d).The studies indicated that,a proper dosage of Bacillus Ch9 could induce the activities of the there digestive enzymes increasing more obviously in a short time,and potentially to promote the digestion and absorption of nutrients.