Development Of A Food Additive For Lactic Acid Bacteria Producing Lipase

Lactic acid bacteria,Lactic acid bacteria)is a recognized food-grade microorganisms.It is widely used in food production,medical engineering,livestock breeding and fermentation industry.Microbial preparation belongs to active probiotic products,which can improve the ecological balance of organisms and improve the health level of subjects.In this experiment,the method of genetic engineering was selected to construct an engineering strain of lactobacillus W1/ p MG36e-lipase-nis I that could overexpress lipase.This lactobacillus does not contain selective markers such as antibiotics and is fully compliant with food grade safety regulations.Experiment amplification lipase gene(lipase)in plant lactobacillus W1 genome as a template,the lipase gene inserted into a plasmid p ET30a(lipase),constructed by e.coli expression vector p ET30a-lipase,then use to buy containing milk peptide chain bacteria resistance genes(plasmid p ET30 a nis I)as a template for nis I amplification,and insert the genes into the expression vector p MG36 elipase,replace erythromycin tag,successfully with lactobacillus expression vector p MG36e-lipase-nis I,The strain W1/p MG36e-lipase-nis I was transformed into W1 by electrotransformation method,and its survival and expression ability in the Nisin environment were detected.The results showed that W1/p MG36e-lipase-nis I grew well in the lactobacillus peptide environment,and W1 had good stability of lipase expression.By comparing the amount of glycerol produced by lipase decomposition of triglycerides,it was concluded that the strain could overexpress lipase.Under the same conditions,10% strains of lactobacillus plantarum were added to the culture medium containing triglycerides.After 4hours of culture,it was concluded that the lipase expression of the recombinant bacteria was more than three times that of the normal strains.Second,with the turning method to expression vector into BL21(e.c.with our fabrication: oli BL21),let the lipase gene(lipase)complete heterologous expression in e.coli,used to study the enzymatic properties of lipase,came to the conclusion that when p H=8,lipase activity was the highest,up to 96.70?/m L,when action temperature of 40?,lipase activity was the highest,up to 110.00?/m L.This lipase has a strong enzymatic stability.Even when p H=2,the activity of lipase is still higher than 38.69?/m L,and the enzymatic property remains at about 40%.Even when the temperature is 60?,its enzymeactivity can be kept above 20%(21.50?/m L).