Regulation Of Lactobacillus Plantarumto Saccharomyces Cerevisiae Ethanol Tolerance And Taxonomic Study Of A Microorganism In Qinghai

It is inevitable that bacterial infection occurs during the production of ethanol from Saccharomyces cerevisiae in industry.The main contaminated strain is lactic acid bacteria.Lactic acid bacteria will compete with yeast for living space,nutrients,etc.,which will adversely affect the production of ethanol.Previous work has shown that Lactobacillus plantarum can regulate ethanol tolerance in S.cerevisiae,but its specific regulatory mechanism is not yet clear.The work of this paper aims to clarify the specific regulation mechanism of Lactobacillus plantarum to yeast ethanol tolerance.In this thesis,the metabolomic technique based on gas chromatography-mass spectrometry is first used to systematically analyze the effect of the coexistence of L.plantarum on the composition and content of metabolites in S.cerevisiae cells.The results show that L.plantarum have effects on carbohydrate,amino acids,fatty acids,and important substances in the TCA cycle such as malic acid,citric acid,and succinic acid,so Lactobacillus plantarum may have an impact on the central metabolism of yeast.Secondly,the way of supplementing carbon source also shows that Lactobacillus plantarum can regulate the reduction of sugar metabolism of Saccharomyces cerevisiae.In addition,the effect of Lactobacillus plantarum supernatant on yeast ethanol tolerance and the effect of Lactobacillus plantarum on ethanol tolerance of S.cerevisiae at different distances were measured by flow cytometry.The results showed that L.plantarum could regulate the ethanol tolerance of S.cerevisiae and is favorable for yeast to cope with ethanol stress.As the distance between S.cerevisiae and Lactobacillus plantarum increases,the ethanol tolerance of S.cerevisiae becomes worse.The strain QTA689T isolated from the Qingtang area of Qinghai is derived from underground sediments in frozen soil.It is a Gram-negative bacterium,aerobic,yellow,non-motile,and spore-free.It is a member of the genus Dyadobacter and is related to Dyadobacter sediminis.The highest similarity is 97.9%.It grows at 4-35℃ and the optimal temperature is 25-28℃.It grows in a pH range of 6.0-9.0(optimal pH 7.0-8.0)and its NaCl tolerance is 0-2.0%(optimal 0-1.0%).The main cellular fatty acids are Summed Feature 3(iso-C15:0 2-OH and C,6:1ω6 c/C16:1ωo7 c),iso-C15:0 and C16:1ω5c.The main respiratory quinone is MK-7,and the main polar lipid is phosphatidylethanolamine.Genome sequencing revealed a genome size of 8.41 Mbp and a G+C content of 46.87 mol%.Based on the whole genome average nucleotide identity(gANI)value,phenotypic data,phylogenetic data and genotype data,strain QTA69T represents a new species of the genus Dyadobacter,whose name is Dyadobacter bucti sp.,And the model strain is QTA69T(=CGMCC 1.13688T=KCTC 72024T).