Bacterial Population Analysis,Isolation And Identification Of Lactic Acid Bacteria And Acetic Acid Bacteria During The Fermentation Of Northwestern Shanxi Acid Porridge

Acid porridge as a traditional fermented food,edible widely,mainly distribute in Western of Inner Mongolia,Northwestern Shanxi,Shanxi province,etc.The aim of this project is to analyze the bacterial population,isolate and identify the lactic acid bacteria and acetic acid bacteria during the fermentation of Northwestern Shanxi acid porridge.Finally,the fermentation technique of Northwestern Shanxi acid porridge is carried out.This work can provide plenty of data for the further industrial production of Northwestern Shanxi acid porridge.In this experiment,three methods(i.e.lysozyme-SDS-proteinase K method,improved CTAB method and improved CTAB-lysozyme method)were used to extract the microbial genome DNA in Northwestern Shanxi acid porridge samples.The results of analyzing the concentration and purity of extracted DNA and PCR products showed that lysozyme-SDS-proteinase K method was the best microbial genome DNA extraction method for DNA extraction from Northwestern Shanxi acid porridge.Lysozyme-SDS-proteinase K method was used to extract the bacterial genome DNA of Northwestern Shanxi acid porridge in six different fermentation periods.The main bacterial populations were analyzed the bacterial phylogenetic tree was constructed.The results showed that lactic acid bacteria and acetic acid bacteria played the main role in the fermentation process of Northwestern Shanxi acid porridge,and their abundance could occupy the 91.74%of the total bacteria.By using dilution spread plate method,47 strains of bacteria were isolated from Northwestern Shanxi acid porridge samples of different fermentation periods.Among 47 strains of bacteria,21 strains were gram-positive,which were identified as Lactobacillus brevis,and 26 strains were gram-negative,which were identified as Acetobacter okinawensis and Acetobacter lambici through colonial and individual morphology observation,physiological and 16S rDNA sequence analysis.The bacteria L.brevis,A.okinawensis and A.lambici isolated in this experiment and the yeasts Pichia kudriavzevii,Issatchenkia orientalis and Saccharomyces cerevisiae isolated from Northwestern Shanxi acid porridge by my a colleague were used to carry out the single strain fermentation and mixed strains fermentation of Northwestern Shanxi acid porridge.The results showed that the sensory evaluation of fermented products of mixed strains fermentation were higher than that of single strain fermentation.Through orthogonal experiments,the theoretical optimum fermentation condition for the Northwestern Shanxi acid porridge was the following:the combination of L.brevis,A.okinawensi,A.lambici,P.kudriavzevii,I.orientalis and S.cerevisiae according to the ratio of 1:2:1:1:1:1,fermentation temperature of 27.5? and fermentation time of 24 h.Under the optimum fermentation condition,the sensory evaluation of the fermented product reached the highest,which was similar to that of traditional Northwestern Shanxi acid porridge,and slightly higher on some aspects such as texture and flavor and a little less excitant odor,eating better.