Isolation And Identification Of Aroma-Producing Strains From Iris Rhizomes And Biosynthesis Of Irone

Irone is the characteristic aromatic component of iris rhizomes and widely used in cosmetics,tobacco and food industries.Iris rhizomes deposited for 2-3 years are used as raw materials for traditional plant extraction method.There are some problems in this production method,such as long period,low yield and high cost.In this paper,the aroma-producing microorganisms were isolated and identified from the rhizome of the iris,and the research on the production of irone with the fresh root powder as raw material was carried out.The exploratory experiment of synthesizing the irone with pseudoionone as the substrate was carried out.Fifteen strains of bacteria and eight strains of fungi were isolated from storaged iris rhizomes,and the fermentation products of the strains were analyzed by high performance liquid chromatography(HPLC)and gas chromatography-mass spectrometry(GC-MS).The results showed that there was a strain producing cis-a-irone.The molecular biological identification of 16SrDNA showed that the strain had a homology of 99%with Bacillus simplex strain and named it YWT-5.Fresh root powder was used as raw material to produce irone by microbial fermentation.The main fermentation process parameters were optimized.10 g/L of glycerol,10 g/L of peptone,1 g/L of potassium dihydrogen phosphate,1.5 g/L of potassium hydrogen phosphate,1 g/L of sodium chloride,0.5 g/L of magnesium sulfate heptahydrate,0.05 g/L of calcium chloride and 5 g/L fresh iris root powder were used as medium.After fermentation at 28? and 200 rpm for 24 h,the yield of cis-a-irone reached 315.95 mg/kg in shake flask.The results of large-scale culture of 10L fermenter showed that when the amount of iris root powder was 5 g/L,the yield of cis-a-irone reached 1073.65 mg/kg after fermentation for 18 h at 28? and 200 rpm.The production of cis-a-irone was about 3.28 times higher than that of shaking flask.The microorganism isolated in the previous stage was used as alternative strains.The LB medium supplemented with 1 g/L pseudo-ionone was used as the fermentation medium.Liquid fermentation was carried out at 30 C and 200 rpm.The results of HPLC rescreening showed that the fermentation product of one strain showed a target peak which was very close to the retention time of a-irone standard.The liquid chromatography-mass spectrometry(LC-MS)results showed that the fermentation broth of the strain contained a-irone.This result indicates that YWT-5 strain can synthesize irone with pseudoionone as a substrate.Morphological observation and molecular biological identification of a fragrant fungus isolated from storaged iris rhizomes were carried out.Molecular biological identification results showed that the fungus had 99%homology with the strain of Bjerkandera adusta,and named it YWN-7.The strain was fermented with PDA solid medium as a fermentation medium,and after fermentation at 30?,75%humidity for 5 days.GC-MS results showed that the fermentation product contained 1-octene-3-ol,n-octanal and phenylacetaldehyde.