Study On High Cell Density Culture Of Lactobacillus Acidophilus IMAU30067

This task mainly studied the high density cultivation of Lactobacillus acidophilus,including preliminary screening of Lactobacillus acidophi lus,culture medium composition and culture conditions,high-density fermentation process.The objective of this task is to provide theoretical basis and practice guidance of Lactobacillus acidophilus industrial production.The test results are as follows:?1?This study filtrated the lactobacillus acidophilus preliminarily by the test of bile tolerance,artificial intestinal gastric juice tolerance,antibacterial and antibiotic resistance.The survival rate of IMAU30067 in artificial gastric juice p H2.5 was 90.80%?gastric juice 3h?and 24.03%?Intestinal juice4h?,21.14%?Intestinal juice 8h?in artificial intestinal juice p H8.0.This shoued that the IMAU30067 had good tolerance to artificial gastric intestinal juice;IMAU30067 had a strong inhibitory effect on e.coli O157:H7,salmonella,shigella,staphylococcus aureus and listeria monocytogenes;At the same time,IMAU30067 showed varying degrees of tolerance to 8antibiotics,it means the IMAU30067 had strong resistance to antibiotics.Therefore,a further study was conducted on IMAU30067.?2?This study based on MRS culture medium and was to static optimize the medium component and culture conditions of Lactobacillus acidophilus IMAU30067 by single factor experiment,orthogonal experiment and response surface optimization experiment.The best culture medium formula:glucose30.00 g/L,maltose 30.00 g/L,Trehalose 20.00 g/L,fish peptone 30.00 g/L,soy peptone 10.00 g/L,sodium citrate 2.29 g/L,sodium acetate 5.74 g/L,K₂HPO₄ 2.29 g/L,Mg S0₄·7H2O 0.80 g/L,potato extract 6.00g/L,histidine0.10g/L,0.3g/L L-cysteine hydrochloridethe.The best culture conditions were:the inoculum size 1×10⁶ CFU/m L,The initial p H value 6.5,The constant temperature 37?.After optimization,the number of viable bacteria can reach 3.85×10⁸ CFU/m L,which was increased by 8.6 times higher than that before optimization.?3?The study researched high-density fermentation process in 5L fermentor,figured out the best fermentation culture conditions:constant p H5.0,gas environment as a nitrogen pressure,the alkali neutralizer is 20%NH ₃H₂0,1×10⁶ CFU/m L quantity of access to Lactobacillus acidophilus IMAU30067 were sent to culture.Compared with static culture,the growth rate and growth cycle of the bacteria in 5L fermentation tank were significantly shortened,and the bacteria concentration was higher.In the end,the number of viable bacteria was 5.72×10⁹ CFU/m L,which was 14.8 times higher than the static cultivation.