Screening And Identification Of Lactic Acid Bacteria With Antimicrobial Activity

In the present thesis, five Koumiss samples, which produced by traditional methods in herdsmen, collected from regions of Inner Mongolia Bayannao’er. Lactic acid bacteria were isolated and identified through traditional methods. And then the lactic acid bacteria were screened for antimicrobial activity by using Escherchia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus as indicator bacteria. Finally, the selected strains of lactic acid bacteria were subjected to research of fermentation properties and stability test. The main results were obtained as follows:A total of22strains were obtained (including16strains of Lactobacillus and6strains of Lactococcus) through separation, purification and identification. After the experiment of determination of antimicrobial activity, six strains including SMN1-4、 SMN2-3、SMN2-5、SMN3-3、SMN4-3and SMN5-2were screened out with higher antimicrobial activity.The properties of catalase, protease and thermal stability test were evaluated concerning the6strains of lactic acid bacteria with desirable antimicrobial activity in fermented milk supernatant was. The results showed that the supernatant of fermented milk by SMN3-3have desirable stability.The effect of fermentation condition (including the temperature, inoculum and fermentation time) on antimicrobial activity were investigated in fermented milk by SMN3-3. The results showed the better antimicrobial activity of supernatant of fermented milk was observed in skim fermented milk by SMN3-3feramtation at at37℃for24h with an inoculation of5×106CFU/mL.The results indicated that the fermented milk supernatant of SMN3-3had better inhibition to enteric pathogens, desirable thermal stability and enzyme stability. It would be provided excellent strains and experimental basis for the research of inhibition to enteric pathogens.