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Microbial ecology of sauerkraut fermentation and genome analysis of lactic acid bacterium Leuconostoc mesenteroides ATCC 8293.

by Plengvidhya, Vethachai

Abstract (Summary)
Previous studies using traditional biochemical methods to study the ecology of commercial sauerkraut fermentations revealed that four major lactic acid bacteria species, namely, Leuconostoc mesenteroides, Lactobacillus plantarum, Pediococcus pentosaceus, and Lactobacillus brevis were involved. Brine samples from commercial fermentation tanks were sampled several times, over a period of 14 days. The samples were plated on MRS agar and selected numbers of isolates for each time point were recovered. A total of six hundred eighty-six isolates were collected for analysis. A database of PCR fragment patterns has been generated by amplifying the intergenic transcribed spacer regions between the 16S and 23S rDNA genes. The 16S rDNA gene has been sequenced to further identify selected isolates. The use of molecular techniques to complement biochemical identification methods has revealed the presence of species not previously reported to be present in sauerkraut fermentations, namely Leuconostoc citreum, Leuconostoc argentinum, Lactobacillus paraplantarum, Lactobacillus coryniformis, and Weissella sp..The ecology of these commercial fermentations has been shown to be more complex than previously reported. Realizing L. mesenteroidesc practical significance in fermentation, bioprocesssing, agriculture, food, and medicine, the whole genome sequence of L. mesenteroides ATCC 8293 originally isolated from olive fermentation has been determined. The chromosome has 2,038,395 bp and contains predicted 1,924 protein-encoding genes. Putative biological functions could be assigned to 54% of the predicted proteins. Consistent with the classification of L. mesenteroides as heterofermentative lactic acid bacterium, the genome encoded all enzymes required for the 6-phosphogluconate/phosphoketolase pathway. Furthermore, L. mesenteroides encodes a number of pyruvate dissipating enzymes that are predicted to catalyze the production of many metabolites leading to various end products of fermentation. A large proportion of the genes are encoded for carbohydrate transport and utilization. The chromosome also contains genes belonging to phage remnants and mobile genetic elements. The genomic sequence also indicated a potential horizontal transfer of genetic information between L. mesenteroides and gram-negative bacteria.The data presented here can help facilitate evaluation of L. mesenteroides as a model organism for studies of heterofermentative LAB metabolism, physiology, and regulation.
Bibliographical Information:

Advisor:Dr. Jeffrey L. Thorne; Dr. Frederick, Jr. Breidt; Dr. James W. Brown; Dr. Henry P. Fleming

School:North Carolina State University

School Location:USA - North Carolina

Source Type:Master's Thesis

Keywords:food science

ISBN:

Date of Publication:08/20/2003

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