| Previous studies showed that lactic acid bacteriacanproduce large amounts of lactic acid and other organic acids,which may decrease the feed pH,as well as increase the number of lactic acid bacteria and inhibit harmful bacteria in feed.In this study,141 lactic acid bacteria was isolated from the digesta and mucosa of pig intestine,of them,10 isolates was screened with potential for fermentation feed production,and the probiotic function and resistance of these isolates were then detected to test whether these species can be used for the production of fermented feed.Finally,these lactic acid bacteria were inoculated in feed,and the characteristics of fermented feed was studied.In general,this thesis consists of three sections.1 Isolation,screenandidentification of lacticacid bacteria from digesta and mucosa of swineThe objective of this study was to isolate and screen the lactic acid bacteria(LAB)with high capability of acidification from pigs.A total of 141 LABwas isolatedfrom colonical digesta and mucosa,cecal digesta and mucosa and feces of pigletsby conventional means.All LAB identified by their morphology,and physiological and biochemical characteristics,were screened for their acidification potential and 10 of strains were finally selected.Those LAB with high capability of acidification,rapid ratefermentation and low finally pHvalue were identified by partial 16S rDNA and the result showed that they were Lactobacillus salivarius,Lactobacillus johnsonii and Enterococcus Faecalis.Overall,our data showed that there were diversespecies of LAB with different acidification capability and fermentation rate,and that some of LAB had high capabilityof acidification and rapid rate of fermentation.2 Study on the resistance and probiotic properties of lactic acid bacteria isolated from the swine gutThe objective of this study was to investigate the resistance and probiotic functionof lactic acid bacteria(LAB).10 lactic acid bacteria isolates from Exp.l were used and explored their resistance to low pH,bile salt,heat,antimicrobial properties and antibiotics challenge.The results showed that L71 and L104 isolates have stronger tolerance against pH 2.5 than other strains,indicating that these two isolates have the strongest tolerance against the acid environment of stomach.The L33,L35,L37 and L104 isolates cantolerance against bile environment in pig intestine.As to antimicrobial properties,the supernatant of L22,L24,L26,L71 and L96 isolates cultures has an antimicrobial effect on enteric pathogenic microorganisms E.coli K88,K99 and Salmonella pullorum.The L96 strain have higher survival efficiency under 60 °C.As to resistance to antibiotics,L71 and L96 strains were sensitive to ampicillin,penicillin,erythmmycin,vancomycine,florfenicol,chloramphenicol,enrofloxacin.In general,our data revealed that L22,L24,L26,L71 and L96 isolates has an antimicrobial effect on enteric pathogenic microorganisms,L71 strain presented a higher tolerance against pH 2.5,antimicrobial effect on enteric pathogenic microorganisms and high capability of acidification,indicating that L71 strainhad a potential for fermentation feed production.3 Characteristics of feed fermented by lactic acid bacteriaIn this study,five lactic acid bacteria isolates were selected as the inoculum for fermentation feed production,and the feed dry matter,pH,the concentrations of lactic acid and volatile fatty acid,and the number lactic acid bacteria and E.coliin these fermented feed were then compared.The results showed that pH of the other fermented feed(except for the L104)were lower than 4.5,and the protein levels are higher than those in the non-fermented feed.The lactic acid content in fermented feed of L26,L35,L37 and L71 were 249 mmol/kg,243 mmol/kg,259.56 mmol/kg and 234 mmol/kg,respectively,which was significantly higher than control group(102.58 mmol/g)(P<0.05).The pH value of the fermented feed inoculated L22 was significantly lower than the control group(P<0.05).There was no difference(P>0.05)in the VFAconcentration(except for the propionate and isovalerate)among L22,L37 and L71 group.When compared with the control,the numbers of the lactic acid bacteria inoculated with these three strains mentioned eariler was increased,while E.coliin these groups was higher(P<0.05).These results indicates that the L22,L3 7 and L71 strains inoculated in the feed can produce a higher concentrations of lactic acid and the numbers of lactic acid bacteria,and further reduce the feed pH and inhibit the numbers of E.coli.These results suggest that the L22,L37 and L71 strains have the potential for fermented feed. |
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