Screening Of Soybean Meal Fermentation Strains,Fermentation Technology And Its Application In Carassius Auratus Culture

Soybean meal has the characteristics of rich crude protein and balanced nutrition.However,due to the existence of anti-nutritional factors in soybean meal,the nutrition of soybean meal in feed is affected.In this study,one bacteria strain named X-2 and one lactic acid bacteria named X-4 that can degrade glycinin were screened from the soil and laboratory-preserved lactic acid bacteria.The strains were identified by morphological observation,physiological and biochemical tests,and molecular biology scientific means.The process conditions of fermented soybean meal with mixed bacteria raw meal were discussed,and a Carassius auratus breeding experiment was carried out on fermented soybean meal using net cages.The main results were as follows:1.Bacteria X-2 and lactic acid bacteria X-4 that can degrade soy globulin were screened from the soil and laboratory-preserved lactic acid bacteria.The strain X-2 and strain X-4 were identified as Bacillus subtilis and Enterococcus faecium respectively by using morphological observation,physiological and biochemical testing,and combined with16S r DNA sequence analysis.2.The fermentation technology of soybean meal by Bacillus subtilis X-2 and Enterococcus faecium X-4 was studied.The suitable fermentation conditions were as below:the ratio of Bacillus subtilis X-2 to Enterococcus faecium X-4 was 2:3,glucose 4.5%,KH₂PO₄0.15%,Mg SO₄·7H₂O 0.1%,anhydrous sodium acetate 0.4%,fermentation time 5days and solid-water ratio 1:1.Under these conditions,the degradation rate of soybean globulin was 36.85%.3.The effects of fermented soybean meal（FSM）on growth,serum indexes,intestinal structure and microbial diversity of Carassius auratus were studied by replacing 0%,20%,40%,60%and 80%fish meal in basic diet（containing 10%fish meal）with FSM.The results showed that there were no significant difference in daily feeding rate（DFI）,survival rate（SR）and feed coefficient（FCR）（P>0.05）.The final body weight（FBW）,weight gain rate（WGR）,specific growth rate（SGR）,hepatosomatic index（HSI）,viscerosomatic index（VIS）,condition factor（CF）and enterosomatic index（ESI）of the FSM60 group were higher than those of FSM0 group.There was no significant difference in crude protein content among groups（P>0.05）.The crude fat content and visceral fat rate（VFR）of FSM60 group were lower than those of FSM0 group,and the crude ash content of FSM0 group was significantly lower than that of other groups（P<0.05）.There were no significant difference in serum low-density lipoprotein cholesterol（LDL-C）,aspartate aminotransferase（GOT）,alkaline phosphatase（AKP）,total protein（TP）,albumin（ALB）,total superoxide dismutase（T-SOD）,malondialdehyde（MDA）and catalase（CAT）between the groups（P>0.05）.The total cholesterol（T-CHO）,triglycerides（TG）,alanine aminotransferase（GPT）,total antioxidant cap-acity（T-AOC）,peroxidase（POD）and immunoglobulin M（Ig M）of the groups which were treated with fermented soybean meal were all higher than FSM0 groups.In the midgut and hindgut,the muscular thickness and villi width of FSM60 group were significantly larger than FSM0（P<0.05）,and the villi length in FSM40 group was higher than that of other groups.The richness and microbial diversity of FSM20,FSM40 and FSM60 groups in midgut and hindgut were higher than those in FSM0 group;The dominant flora at genus level in midgut and hindgut was Cetobacterium.In conclusion,fermented soybean meal instead of fish meal can improve the growth,metabolism,intestinal structure of Carassius auratus and intestinal microbial diversity.