Molecular Characteristics Of 32 Strains Of Saccharomyces Cerevisiae From Different Dough Starters And Their Fermented SFS Flavors

This study aims to investigate the relationship between molecular characteristics of 32 strains of Saccharomyces cerevisiae from different dough starters and their fermented flavors.The gas production value and acid-producing efficacy of Saccharomyces cerevisiae were detected by Wickerham's method and pH meter respectively.Further investigations revealed that volatile compounds in sterile flour solution fermentation were determined using HS-SPME-GC-MS which is high efficient technology.The genetic relationships among the 32 yeasts were determined by pulsed-field gel electrophoresis(PFGE).After the total protein was extracted by the standard methods,gel electrophoresis followed by SDS-Page was used to separate and identify the initially different proteins.The main results are as follows: 1.We collected 32 samples of dough starters from different homemade workshops across three countries then we isolated and identified the main prevailing strains Saccharomyces cerevisiae.2.The glucose and sucrose are the best fermentable carbohydrates for gas producing ability and acidity.3.We compared the gas producing value and the acid-producing ability of 32 strains of S.cerevisiae by Wickerham's method and Miniaturized Durham tubes.The results showed that SC-N6,SC-T6,SC-Y2,SC-Y10,and SC-Y12 yeast strains had the highest gasproducing efficiency,SC-N1,SC-X1,SC-Y2,SC-T2,SC-T3,SC-X3,SC-Y4,SC-N4,SC-N5,SC-Y5,SC-Y6,SC-Y8 and SC-Y12 yeast strains presented the best acidproducing ability after 10 h of fermentation,SC-Y2,SC-Y10 and SC-Y12 had a higher gas-producing efficiency and a better acid-producing ability.4.The optimum fermentation phase was 4-6 hours,which could be seen from the pH values and gas volumes.5.We analyzed the volatile organic compounds(VOC)produced in sterile flour solution(SFS)fermentation by yeasts.The flavors were determined using HS-SPME-GC-MS technology.This technique provided a non-invasive,clean and selective method to characterize the volatiles.We found a total of 39 kinds of flavors;SC-N1,SC-N3 and SCY12 yeast strains produced more than 18 types of volatile compounds.6.The genetic relationships between 32 strains of yeasts were determined by pulsed-field gel electrophoresis(PFGE)methods and analyzed by BioNumerics software.Cluster result showed the genetic relationship among the 32 strains.Yeast strains from Hubei,Shandong,and Hebei provinces possessed similarities in acid-producing ability,varieties of VOC,and PFGE fingerprint.7.The analysis of the total protein from the 32 different kinds of S.cerevisiae was done by SDS-PAGE technology and subsequently cluttered by BioNumerics software.SC-Y10 and SC-Y12 had the highest gas-producing efficiency and the best acid-producing ability,at the same time both have similarities of protein samples.This study aids in providing a better base for yeast strain selection of CSB.