Investigation On Bacteriocins Produced By Lactobacillus Acidophilus Fermented With Cottonseed Meal Mixed Substrates

In this paper, Lactobacillus acidophilus was selected as starting strain in this study,screening outLactobacillus acidophilus with high-effective bacteriocin with broader antimicrobial spectrum. Biologicalcharacteristics and purification of bacteriocin were studied. The subject of study focused on the effect ofdifferent fermentation substrate on antimicrobial activity and nutrient content of fermented feed with L.Acidophilus. Optimize the inorganic ion in fermented feed, which was evaluated via quantity of L.Acidophilus and the activity of bacteriocin. At the same time, Explore the effect of different drying methodand package on the antibacterial activity of bacteriocin of fermented feed with L. Acidophilus. Thisresearch is composed by four parts. The results were as follows:Experiment1, In this study, three Lactobacillus acidophilus were included to investigate theirantimicrobial activity of the supernatants of fermentation culture with the agar diffusion method. Inhibitiveeffects of hydrogen peroxide and organic acid were ruled out in the subsequent experiments. Antimicrobialactivity of the culture supernatant of Lactobacillus acidophilus J2was detected. The treatment of proteasescould completely abolish the antimicrobial activity of the supernatant. These results demonstrated that theantimicrobial substance belonged to bacteriocin family.Experiment2, A bacteriocin-producing Lactobacillus acidophilus was screened from the strainspreserved in our laboratory, the purpose of this study is to investigate the characteristics of the bacteriocinby using agar diffusion method. In this study, The bacteriocin was extremely heat stable (30min at121℃）, and exhibited antibacterial activity at pH3.0~6.0. Some activity was lost disposed by organicsolvents. It was found to be sensitive to proteolytic enzymes (trypsin, papain, proteinase K andbromelain),but insensitive to pepsin.The bacteriocin showed a broad spectrum of inhibitory activity bothagainst Gram-positive bacteria(Staphylococcus aureus and Bacillus subtilis) and Gram-negativebacteria(Escherichia coli and Salmonella).Experiment3, Isolation and identification of bacteriocin produced by Lactobacillus acidophilus J2was studied in this paper. In this study, The bacteriocin was purified by60%ammonium sulfateprecipitation followed by Sephadex G-50gel filtration chromatography. The results showed that thespecific activity of purified bacteriocin reached386.3AU/mg. The final yield of bacteriocin was26.99%and the specific activity was increased by25.08fold. The molecular weight of the bacteriocin wasabout7800-14400u, as determined by Tricine-SDS-PAGE. Experiment4, Based on the experiments above, different fermentation substrate on antimicrobialactivity of fermented feed with L. Acidophilus was studied. Explore the effect of inorganic ion,differentdrying method and package on the antibacterial activity of bacteriocin of fermented feed with L.Acidophilus. The results indicated that there was not significant difference between cottonseed meal andsoybean meal. The optimal inorganic ion additive amount consisted of0mg/kg MgSO4,275mg/kgC6H17N3O7,2.5mg/kg MnS04,270mg/kg K2HPO4. More over, the fermentation product showed excellentstabilities after vacuum dry treatment and during vacuum packing storage...