Abstract: This study was conducted to investigate the mechanism of fructan metabolism in lactic acid bacteria in order to develop low-fructan fermented foods. One strain capable of utilizing fructan, 19M03, was selected from 287 lactic acid bacteria strains isolated from sourdough. Then, the strain was subjected to whole-genome sequencing and its fructan metabolism mechanism was analyzed by using high-throughput sequencing and bioinformatic techniques. The sequencing results showed that the genome of strain 19M03 contained one chromosome and nine plasmids, with a total length of 3 246 316 bp, GC content of 44.53%, 3 084 coding genes, 66 tRNAs and 16 rRNAs. The phylogenetic relationship analysis showed that strain 19M03 belonged to Lactiplantibacillus plantarum. The results of gene function annotation showed that its genome sequence contained a total of 357 genes encoding carbohydrate-active enzymes (CAZymes) and 351 genes encoding carbohydrate transport proteins in the Clusters of Orthologous Groups of proteins (COGs), Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and CAZy databases, as well as 12 genes related to fructan metabolism and transport, respectively. Based on the metabolic relationship of these genes in the KEGG database, a fructan metabolism model was proposed for 19M03. The model resolved the cellular localization of the fructan hydrolysis process and related catalytic reactions (both intracellular and extracellular), the specific transporters of fructooligosaccharide and fructose in the cell membrane (IIABCFOS, IIABCDfru and IIABCfru), the intracellular pathways of fructose catabolism (n = 4) and fructose anabolism (n = 1), and the genes encoding all related enzymes. In addition, resistance and virulence gene analyses demonstrated that 19M03 had a good safety profile. In conclusion, these results provide an important theoretical basis for elucidating the fructose metabolism mechanism of lactic acid bacteria so as to provide high-quality strain resources for the development and application of low-fructofuran functional foods in the future.

Key words: fructan metabolism; whole-genome sequencing; metabolic mechanism