Study On Medium Optimization And High Density Fermentation Process Of Lactobacillus Acidophilus LA-06

Lactobacillus acidophilus LA-06 has the characteristics of acid resistance and bile salt resistance.It is a probiotic that can help the human body effectively regulate immunity and improve the intestinal flora.However,due to its slow growth rate,low cell density,and complex nutrient requirements,the scope of industrial application is limited.Therefore,the high-density culture of Lactobacillus acidophilus LA-06 was carried out,and the medium optimization,culture condition optimization and high-density culture were carried out by single factor test,response surface optimization and orthogonal test to obtain Lactobacillus acidophilus with high viable count,which provided basic data for freeze-drying and preparation of lactic acid bacteria starter.The test results are as follows:（1）Taking Lactobacillus acidophilus LA-06 as the research object,the medium composition was optimized by single factor test and response surface optimization method.The optimum medium formula of Lactobacillus acidophilus LA-06 was maltose 36.36 g/L,fish peptone 92.18 g/L,sodium citrate 2.58 g/L,sodium acetate 6.44 g/L,dipotassium hydrogen phosphate 2.58 g/L,Mn SO₄·H₂O 40.00 mg/L,Mg SO₄·7H₂O 200.00 mg/L,aspartic acid 30.00 mg/L,Tween 1.00 g/L.（2）The culture conditions of Lactobacillus acidophilus LA-06 were optimized by orthogonal test.The optimum culture conditions of Lactobacillus acidophilus LA-06 were as follows:fermentation temperature 39°C,inoculation amount 1%,initial p H 6.0.After optimization,the number of viable bacteria in the fermentation broth reached（2.38±0.24）×10⁹CFU/m L,which was 2.90 times higher than that in the MRS medium（8.21±0.06）×10⁸CFU/m L before optimization.（3）On the basis of the above optimization experiments,the high-density culture of Lactobacillus acidophilus LA-06 was carried out in a 5 L high-density fermentation tank,and the MRS medium was used as the control group.During high-density culture,the growth rate of Lactobacillus acidophilus LA-06 in the optimized medium was faster,the logarithmic phase was longer,and the cell concentration was higher.At the end of fermentation,the viable count of Lactobacillus acidophilus LA-06 fermentation broth in the optimized medium was（4.84±0.26）×10⁹CFU/m L,which was 3.56 times of that in MRS medium（1.36±0.15）×10⁹CFU/m L.