The Adsorption Of Aflatoxin B₁ By Lactic Acid Bacteria

Aflatoxin?AFT?is a class of chemically similar compounds,which are derivatives of dihydrofuran coumarin.Aflatoxin is a secondary metabolite mainly produced by aspergillus flavus and aspergillus parasitic,which is widely found in forage and food.Aflatoxin B₁ is the most toxic of aflatoxin,It can cause a series of acute poisoning symptoms,and also has carcinogenic toxicity,genotoxicity,genotoxicity and immunotoxicity.AFB₁ affects economy and threatens human health.The method of remove AFB₁ can mainly devide into three broad categories:physical detoxification,chemical detoxification and biological detoxification.Physical detoxification and chemical detoxification have disadvantages of high cost,and may destroy nutrient component in food.But biological detoxification has advantages of green,efficient and low cost,it has drawn wide attention because of its advantage.Lactic acid bacteria are widely recognized as a food-grade microorganism in the human intestine,which is widely recognized in the human intestine.In this study,the adsorption capacity of Lactic acid bacteria which is stored in laboratory to AFB₁ was compared,and the adsorption rate was determined by HPLC.The results showed that all the four strains of lactic acid bacteria could adsorb AFB₁.Among them,Lactobacillus plantarum P1,a Lactobacillus plantarum strain isolated from Sichuan pickles stored in the laboratory,had the highest adsorption rate.In order to provide sufficient experimental bacteria for subsequent experiments,and save production cost,the growth conditions of Lactobacillus plantarum P1 were optimized in this experiment.Drawing the Growth Curve of Lactobacillus plantarum P1 by Bioscreen C Automatic Microbial Growth Curve Analyser.The results showed that the bacteria grew logarithmically in5-15 h.In this study,Lactobacillus plantarum P1 was cultured for 15 h.The optimum single factor conditions were as follows:initial inoculation amount 3%,initial pH 6,culture temperature 37?,tomato juice addition amount 4%,salt concentration 1%.On this basis,Plackett-Burman?PB?test was designed to screen the most significant factors affecting the growth of Lactobacillus plantarum P1.The results showed that the three most significant factors were initial pH,initial inoculation volume and culture temperature.Under these conditions,response surface methodology was used to optimize the culture conditions to achieve high density culture.Response surface experiments were carried out to analyze the three factors.Finally,the variance analysis showed that the quadratic regression model?P<0.0001?was very significant,the missing item?P=0.7718>0.05?was not significant,and the correction coefficient R²_Adj=0.9588 of the model could explain the change of the number of live lactic acid bacteria.The optimum growth conditions of Lactobacillus plantarum P1 were as follows:initial pH 6.1,initial inoculation 2.9%and culture temperature 37.1 C.Under these conditions,the number of live bacteria of Lactobacillus plantarum P1 could be predicted to reach 10.73 lg?cfu/mL?.Finally,the validity of the model is proved by the validation experiment.Lactobacillus plantarum P1 was used as adsorbent to study the adsorption characteristics of the bacteria to AFB₁.The results show that the adsorption rate of Lactobacillus plantarum P1 to AFB₁ decreases with the increase of the concentration of AFB₁.With the increase of bacterial concentration,the adsorption rate of Lactobacillus plantarum P1 to AFB₁ increased gradually.The adsorption of Lactobacillus plantarum P1 to AFB₁ was a fast process.The adsorption rate reached the highest level in about 30minutes,and then the adsorption rate decreased,and the adsorption rate reached equilibrium in 3 hours.With the increase of adsorption temperature,the adsorption rate of Lactobacillus plantarum P1 on AFB₁ increased,and the effect of temperature on adsorption was significant.The adsorptive rate of Lactobacillus plantarum P1 under artificial gastrointestinal juice decreased to a certain extent,and the adsorptive rate of AFB₁ increased significantly after heat killed treatment.Fiting with Langmuir,Freundlich,Redlich-Peterson and Temkin adsorption isotherms,the biosorption process could be fitted with 4 isotherm models.The correlation regression coefficients showed that the biosorption process could be fitted well with Langmuir adsorption isotherms.It is known from the Langmuir that in the adsorption process,there was a single molecular layer adsorption,and the adsorption was more favorable when the concentration of AFB₁ were higher.Fiting with pseudo-first-order,Elovich and pseudo-second-order,the correlation regression coefficients showed that the biosorption process could be fitted well with Elovich models.They indicated that there were chemisorption and heterogeneous diffusion process in the adsorption process.