title: Identification of key micro-organisms involved in Douchi fermentation by statistical analysis and their use in an experimental fermentation.
abstract: OBJECTIVE
  To screen and identify safe micro-organisms used during Douchi fermentation, and verify the feasibility of producing high-quality Douchi using these identified micro-organisms.
  
  
  RESULTS
  PCR-denaturing gradient gel electrophoresis (DGGE) and automatic amino-acid analyser were used to investigate the microbial diversity and free amino acids (FAAs) content of 10 commercial Douchi samples. The correlations between microbial communities and FAAs were analysed by statistical analysis. Ten strains with significant positive correlation were identified. Then an experiment on Douchi fermentation by identified strains was carried out, and the nutritional composition in Douchi was analysed. Results showed that FAAs and relative content of isoflavone aglycones in verification Douchi samples were generally higher than those in commercial Douchi samples.
  
  
  CONCLUSIONS
  Our study indicated that fungi, yeasts, Bacillus and lactic acid bacteria were the key players in Douchi fermentation, and with identified probiotic micro-organisms participating in fermentation, a higher quality Douchi product was produced.
  
  
  CONCLUSIONS
  This is the first report to analyse and confirm the key micro-organisms during Douchi fermentation by statistical analysis. This work proves fermentation micro-organisms to be the key influencing factor of Douchi quality, and demonstrates the feasibility of fermenting Douchi using identified starter micro-organisms.
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: C
authors.identifier: http://orcid.org/0000-0002-3407-2884
authors.initials: C
authors.lastname: Chen
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: J Y
authors.initials: JY
authors.lastname: Xiang
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: W
authors.initials: W
authors.lastname: Hu
authors.affiliation: School of Life Sciences, Jilin Agricultural University, Changchun, China.
authors.forename: Y B
authors.initials: YB
authors.lastname: Xie
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: T J
authors.initials: TJ
authors.lastname: Wang
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: J W
authors.initials: JW
authors.lastname: Cui
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.|Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun, China.|National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, China.
authors.forename: H
authors.initials: H
authors.lastname: Xiang
authors.affiliation: School of Life Sciences, Jilin University, Changchun, China.|Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun, China.|National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Xie
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D058645:Denaturing Gradient Gel Electrophoresis; D005285:Fermentation; D005658:Fungi / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D007529:Isoflavones / Q000378:metabolism; D007777:Lactobacillaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D013025:Glycine max / Q000382:microbiology*
chemical_list: D000596:Amino Acids; D007529:Isoflavones
keywords: Douchi; PCR-DGGE; food safety; free amino acids; soybean isoflavones; statistical analysis