Screening And Fermentation Characteristics Of Lactobacillus Oligofermentans From Chinese Sauerkraut

Food fermentation is to improve the flavor or preserve food by microbial activities.There are many kinds of fermented food.Fermented vegetables is a typical fermented food,which is fermented by indigenous lactic acid bacteria(LAB).The sauerkraut in Northeast China is typical and favorite kind of fermented vegetables because of its easy-making,special flavor and good taste.These characteristics of Chinese sauerkraut are pleasant for the public.The production of fermented vegetables depends on microorganisms.Investigation of microbiological dynamics during vegetable fermentation,is benificial to control fermentation,but also convenient to explore all kinds of probiotic microorganisms.In the previous study,we firstly found that Lactobacillus oligqfermentans existed in the vegetable fermentation system by cloning libraries.In order to study the function and application potential of L.oligofermentans,we focused on the following studies.First,we used the media containing pentose to screen microorganisms from fermented vegetables and identified different species by 16S rDNA sequencing.After obtaining L.oligofermentans,we inoculated sauerkraut with Lactobacillus oligofermentans AMKR18,L.oligofermentans SH-X4,L.oligofermentans SH-Y15,L.curvatus and L.plantarum as starter cultures.During the fermentation,the changes in pHs,titration acid,nitrite,soluble sugar,soluble protein,lactic acid and acetic acid content were monitored.And the dynamics of lactic acid bacteria and aerobic bacteria were determined.Then the microbial diversities of sauerkraut with different inoculants were analyzed by Illumina Miseq Sequencing.The growth curve of strains were determined by Spectrophotometer.Then the acid resistance,salt tolerance,low-temperature resistance and degradation ability of nitrite were determined in different environments.The results are as follows:(1)417 lactic acid bacterial strains were isolated,which belong to Pediococcus pentosaceus,Weissella cibaria,Leuconostoc citreum,Leu.Mesenteroides,Leu.pseudomesenteroides,Lactococcus lactis,Lactobacillus sakei,L.plantarum,L.brevis,L.curvatus,L.coryniformis and L.oligofermentans.Among these strains,L.oligofermentans,P.pentosaceus and Leu.pseudomesenteroides were isolated for the first time from sauerkraut.(2)The results of inoculating fermentation showed that:?sauerkraut with inoculation had lower pH value than the control.The accumulation of titration acid and the consumption of soluble sugar and protein were more rapid,which indicated that inoculation could accelerate the fermentation process.?The inoculation of L.oligofermentans decreased soluble sugar faster.And the nitrite peak was lower than other treatments,with nitrite content was lower than other treatments.?Using Illumina Miseq Sequencing to analyze microbial diversity in Chinese sauerkraut system,the results show that,at the phylum level,the detected microorganisms were mainly subordinate to Firmicutes and Proteobacteria.In all treatments,lactic acid bacteria dominated in the fermentation process,and its relative abundance are more than 70%.(3)We screened and obtained strains L.oligofermentans SH-Y15.The results show that the isolated L.oligofermentans SH-Y15 has good growth ability.And it still showed remarkable growth at 10 ? or pH=3.It showed better low-temperature resistance and acid resistance.Futhermore it also has significant ability to degrade nitrite at low temperature,which can be considered to be used in the low-temperature environment where nitrite degradation is needed.The mechanism of nitrite degradation of L.oligofermentans needs further study.