Study On The Stereoselective Behaviors Of Chiral Pesticide Paclobutrazol And Its Influence On Microorganism Community During The Food Fermentation Process

Pesticides have been widely used in the agricultural production process for improving the quality and increasing yield.However,unscientific and unreasonable use of pesticides could bring the potential threat for environmental safety and human health.The isomers always have differences in bioactivity,toxicity or degradation behaviors.Therefore,the stereoselective pollution produced by isomers could not be ignored.Paclobutrazol as a chiral compound and the isomers of paclobutrazol have different bioactivities: the activtity of(2S,3S)-paclobutrazol is plant growth regulator and(2R,3R)-paclobutrazol has high fungicidal activity.Fermentation foods are producted under the action of microorganisms,which have lots of benefits to human health and unique flavor.However,there are potential food safty risks because of improper processing or unqualified raw materials.There were only a few researches about the stereoselective behaviors during the food fermentation process.This study investigated the stereoselective behaviors of paclobutrazol during the fermentation process of yogurt,wine and pickled vegetables.And the fermentation microbial community structures and diversity informations were obtained by High-throughput sequencing.The influences of paclobutrazol on fermentation microbial and the impacts of microorganism on the stereoselective behaviors were investigated.The main results were as follows:1.The qualitative and quantitative analysis methods of paclobutrazol in yogurt,wine,and pickled vegetables samples were set up.The resolution of enantiomers was used by High Performance Liquid Chromatography couped with chiral stationary phase.The QuEchERS was used as the sample pretreatment method to extraction,purification and enrichment of the paclobutrazol from different samples.2.The results of stereoselective behaviors demonstrated that paclobutrazol did not show stereoselection during the fermentation process of yogurt and wine,and did not degrade.However,for the pickled vegetables fermentation process,paclobutrazol enantiomers showed significant inversion of S-enantiomer into R-enantiomer,and vice versa the S-paclobutrazol showed a significantly higher inversion tendency than the R-paclobutrazol.During pickled Chinese cabbage fermentation process,paclobutrazol enantiomers showed significant stereoselective degradation but not in pickled cucumber fermentation process.3.High throughput sequencing of paclobutrazol-yogurt fermentation samples: the main bacterial genus found in yogurt was Streptococcus and Lactobacillus.As the fermentation process proceeds significant differences of Lactobacillus abundance was found(between 0 d and 15 d).The results showed paclobutrazol had no significant influences on the main yogurt bacteria but other low abundance bacteria(Staphylococcus,Bacillus,and Acinetobacter).Paclobutrazol could inhibit the KEGG function of Xenobiotics biodegradation and metabolism and metabolism of other amino acids compared with blank control.4.High throughput sequencing of paclobutrazol-wine fermentation samples: The main bacterial genus found in wine with fermentation powder was Gluconobacter and Acetobacter,and the main fungi genus was Saccharomyces because the fermentation powder consisted of Saccharomyces cerevisiae.The main bacterial genus found in wine under natural fermentation was Gluconobacter and Pseudomonas,and the main fungi genus was Pichia.Fermented time would make the significant difference of Lactobacillus between groups,but paclobutrazol had no significant influence on the wine bacteria and fungi.5.High throughput sequencing of paclobutrazol-pickled vegetables fermentation samples: The main bacterial genus found in pickled Chinese cabbage samples was Lactobacillus,and found in the pickled cucumber samples was Weissella,Lactobacillus,Lactococcus.The main fungi genus in pickled vegetables was Candida.Pseudomonas and Serratia was detected in pickled vegetables samples which could degrade paclobutrazol reported in other researches.Paclobutrazol had no significant influence on the microbial community structures and function of bacterial.In pickled cucumber fermentation system,R-paclobutrazol might inhibit Erwinia,Exiguobacterium,Fusobacterium bacterial genus and Cladosporium fungi genus,Race-paclobutrazol might show the inhibition on Fusobacterium bacterial genus and Cladosporium,Mycosphaerella fungi genus.The above results confirmed R-paclobutrazol had the higher fungicidal activity than S-paclobutrazol.In pickled cucumber samples' bacterial COG function,Race-paclobutrazol could make the inhibition on the Energy production and conversion and R-paclobutrazol inhibited Nucleotide transport and metabolism.In addition,R-paclobutrazol showed inhibition on five KEGG mentalisms which contained Nucleotide metabolism,Replication and repair,Translation,Cell growth and death,and Transcription.