| Pericarpium Citri Reticulatae‘Chachiensis'(PCR-Chachiensis)is an herbal medicine made from dried peels of Chachiensis.It can be used in cooking,snacks and tea,but also widely used in traditional Chinese medicine with high medicinal value.Characterizing the microbial community in PCR-Chachiensis is crucial to study the effect of miocrobiota during its ripening,and it could provide theory support for further characterization of PCR quality from microbial and chemical aspects.In the present study,PCR-Chachiensis,made from ‘Chachiensis' was thoroughly investigated through microbial diversity sequencing technique and metabolomic analysis.The main results can be summarized as follows:(1)The free and bound polyphenol in PCR samples with different aging years and different origins were extracted and analyzed.In the first 5 years of ripening,free phenolics content from three sample groups showed the same variation trend,first increased then decreased.Totally,eleven phenolic compounds including seven flavonoids and four phenolic acids were identified through HPLC-PAD.Among the four phenolic acids,ferulic acid was the most abundant one,followed by chlorogenic acid,caffeic acid and p-coumaric acid.In the free phenolic fraction,p-coumaric acid increase,and chorogenic acid decreased during aging.In contrast to the other three phenolic acids,which mainly existed in free extracts(about 80%),ferullic acids was contributed mainly by the bound phenolic fraction(about 50%),and showed significant decrase trend in the first 4 years of repening.Through the comparion,it is suggested that phenolic acid components in different fraction can be used as new indicator to quality PCR-Chachiensis.(2)High throughput sequencing of 16 S rDNA amplicon were performed to analyze the bacterial diversity.The depth of sequencing was sufficient to cover the abundant bacterial community in all samples.About 30000 clean reads were obtained for each sample,and totally 440 OTUs were generated from 38 samples.The sequencing results showed that the most abundant bacteria belong to Proteobacteria(63.41%),Cyanophyta(22.11%)andFirmicutes(12.30%).In the species annotation of the most abundant 100 OTUs,a total of25 family,19 genus were obtained.The results indicated Bacillus,Lactococcus and Pseudomonas was the dominant bacteria.Furthermore,Lactococcus,Enterococcus,Mycobacterium,Bacillus,Arthrobacter and Pseudomonas,which were widely present in various fermented foods and beverages,were also detected in PCR-Chachiensis with high relative abundance(76.842%).(3)By using Venn method to analyze the OTU distribution,39.09% of bacterial OTU was shared between three sample groups.Among the most abundant 30 OTUs,the proportion of bacteria OTU in three groups increase to 61.11%,indicating that there were similar dominnat bacterial communities in three sample groups.(4)The metabolites in volatile oil were identified and quantitated by GC-MS.About100 compounds were identified in both sample groups.Methyl 2-(methylamino)benzoate,the unique ingredient of PCR-Chachiensis was found in all samples.The change in the content of methyl 2-(methylamino)benzoate was consistent in two sample groups.It increased in the first three years,then decreased during aging.As the highest content of volatile oil,the content of D-limonene decreased by 34.11% in Y group samples,16.20% in T sample group in the first three years,and then increased with the aging time.The relationship between the volatile oil component(variables=40)and the bacterial community(variables=25)was analyzed by PLS analysis.The results suggested that 10 variables including Pseudomonas donate a large contribution in the projection plan,and these abundant bacterial community may have an effect on the metabolite changes of volatile oil. |
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