Mechanism Of Degradation Of Patulin By Lactobacillus Casei YZU01 And Its Application

The prevention and control of patulin(PAT)contamination in food is imminent because it has become an important factor that threatens the health of consumers,causes economic losses,and undermines national food safety strategies.Control of PAT by biological method has become a research hotspot because of the advantages of economical,efficient,safe,and so on,and has shown great application potential.As a widely used biological control agent,lactic acid bacteria(LAB)have great application potential in the control of PAT contamination.However,the resources of LAB strains that can degrade PAT,the mechanism of degradation of PAT,and the practical application effects need to be explored and analyzed.Therefore,the research contents of this thesis are as follows:screening LAB that can degrade PAT,molecular identification of LAB,and research on the mechanism of PAT degradation by LAB;research on the toxicity of PAT degradation products by LAB;analysis of the effect of LAB on PAT control in food.The results of the paper are as follows:1.A strain of LAB that can efficiently degrade 95%of PAT(10.9 ?g/mL)within 48 h was screened out.The strain was identified as Lactobacillus casei by morphological and molecular biology identification and named as L.casei YZU01.The research on characteristics and mechanism of PAT degradation by L.casei YZU01 found that this strain has the best degradation effect on PAT at 37? or pH 5,and the PAT degradation rate was 94.77%and 95.14%,respectively.Furthermore,the PAT degradation rate was increased accompanied by the increase of L.casei YZU01 concentration and was decreased accompanied by the increase of initial PAT content.The residual PAT at a concentration of 4.1 ?g/mL was degraded to 1.78 ?g/mL by the fermentation broth after filtering out L.casei YZU01 cells in the co-culture system with PAT,which indicated that L.casei YZU01 mainly catalyzes PAT degrading by extracellular enzymes.In addition,PAT content was reduced from 10.9 ?g/mL to 7.64 ?g/mL by the L.casei YZU01 cell wall,which indicated adsorption PAT by the L.casei YZU01 cell wall is another way to remove PAT.2.The toxicity of PAT degradation products by L.casei YZU01 was analyzed.The results showed that feeding PAT could increase the drinking water and food intake of the mice,the body weight was also significantly increased,the body growth was abnormal,the organ index was significantly decreased,the liver and kidney tissues were oxidatively damaged,the intestinal flora was disturbed,and the normal structure of the intestine was destroyed.destroy.However,the above toxicity caused by PAT was not found in the group treatment with PAT degradation products which indicating that the degradation product had no toxic effect.In addition,the study found that L.casei YZU01 can alleviate the toxic effects of PAT in mice in vivo,because the toxicity characteristics caused by PAT was eliminated after treated by L.casei YZU01.3.The effect of L.casei YZU01 in controlling PAT contamination in food and its impact on the food quality has been studied.The results showed that L.casei YZU01 can completely remove PAT(10.9 ?g/mL)in raw apple juice within 36 h,and in commercial apple juice within 48 h.The content of citric acid,tartaric acid,fumaric acid and acetic acid in apple juice was increased,but the content of glucose and malic acid was decreased.Furthermore,nonenzymatic browning reaction of fruit juice was not caused,the red and green a*value of juice was increased,the brightness L*value,the yellow and blue b*value value has no change,and the light transmittance of apple juice was decreased,which indicated it has less impact on the quality of juice after treatment with L.casei YZU01.