Application Of The Different Sources Of Lactic Acid Bacteria, Antibiotic Resistance And Susceptibility Of Lactic Acid Bacteria

Lactic acid bacteria(LAB) exists widely in the natural world and has high value of application in the food industry,agriculture,medicine and other fields which have closely relationship to the human.Antibiotics have been widely used in bacteria caused infections disease treament,however,they also brings hostile effects such as antibiotic resistance,the number and types of antibiotics resistant bacteria,including varieties of LAB,increased rapidly.The LAB carrying transferable antibiotics resistant factors will bring harmful consequences to consumers when they are used as starter.LAB were isolated from different samples of:koumiss,yogurt,acid camel milk, acid milk clot collected in the pastoral areas,in Xinjiang province,China;dairy cake,collected in Yunnan province,China;healthy infant faeces,collected from Yangzhou,Jiangsu province,China,and dairy products,bought from local market.The isolates were identified with physiological and biochemical methods.Antibiotics resistance of the isolated LAB was tested.SDS combined with 47℃training was used to eliminate the antibiotics resistance factors.The effects of elimination on the growth,the fermentation performance and the stability during storage of the antibiotics sensitance eliminated strains were studied.These strains were used to produce soymilk and the results were descripted as follows:1.A total of 45 strains of LAB were isolated and identified from varieties of samples of different sources of which16 strains of LAB isolated from Xinjiang include five L.sake,two L.delbrueckii subsp.Bulgaricus,two L.plantarum,one L.alimentarius,one L.casei,one L.brevic,two E.faecium,one L.Lactic subsp. Cremoris,one S.bovis;eleven strains of LAB isolated from Yunnan dairy cake,there L.delbrueckii subsp.bulgaricus,two L.helveticus,two L.casei subsp tolerans,two L.viridescens,one E.faecium;eleven strains of LAB isolated from the local dairy include six L.delbrueckii subsp.bulgaricus,five Str.thermopilu;six strains of LAB were isolated from the healthy infant faeces,they were all L.rhamnosus.2.The result of antibiotics resistance testing showed that 35.6%(16/45)of the strain was resistant to penicillin G,15.6%(7/45)was resistant to vancomycin;73.3%(33/45)was resistant to erythromycin,48.9%(22/45)was resistant to tetracycline,20%(9/45)was resistant to amoxicillin,17.8%(8/45)was resistant to Ceftriaxone,68.9%(31/45)was resistant to gentamicin,64.4%(29/45)was resistant to norfloxacin,24.2%(11/45)was resistant to chloramphenicol.Among them,the strains which isolatied from Xinjiang province showd high level resistant to erythromycin,gentamicin,norfloxacin,13 strains were multi-drug resistant;the strains which isotatied from Yunnan province showd high level resistant to erythromycin,7 strains were multi-drug resistant;the strains which isolatied from bought dairy showd high level resistant to gentamicin,9 strains were multi-drug resistant;the strains which isolatied from the infant intestinal showd high level resistant to gentamicin,5 strains were multi-drug resistant.3.The result of antibiotics resistant elimination testing showed that 1/8 MIC concentration of SDS combined with 47℃incubation were used to eliminate the antibiotics resistance of LAB,and the result showed that treated 96h under above mentioned conditions,the antibiotics resistance of the LAB could be the totally eliminated,fifty continuous generations later the antibiotics sensitive was found to be stable.However after the elimination of antibiotics resistance,the growth rate of XL1,XN₅3 had been decreased,the acid production capacity of strain G4 and 90-M2X had been reduced by 13%and 28%,respectively;after storaged at 4℃for two weeks, the survival rates of XN₅3,YC-380 and XL1 were 0.3%,0.7%and 1.5%of their parents, respectively.4.Taming can shorten the Antibiotic-sensitive LAB's curd time by 0.5 to 2 hour,and increase the LAB's acid production by 5 to 15°T.The proportion of soybean and water,streptococcus and bacilli,and the quantity of sugar,butter and starter were studied by the soymilk fermentation test.The result showed that the best ration of soybean and water is 1:8(W/W),the best conment of sugar and butter is 8.0%and 1.0 %respectively.There percent starter,mixed by CP7 and BG at ration of 1:1,incubated for 8h at 42℃,could produce fine sensory quality.