The transcriptional regulation effects of histidine, isoleucine and glutamate on free exopolysaccharide biosynthesis of 937.

INTRODUCTION

The free exopolysaccharide (f-EPS) produced by is a natural texture modifier and has a variety of prebiotic activities. Our previous studies showed f-EPS production from 937 was increased 2-fold in the presence of 15 mM of glutamate, isoleucine, and histidine in the chemically defined medium.

METHODS

In this study, we used transcriptomics and qPCR to further explore the specific mechanism of the enhanced effect of 3 amino acids on the f-EPS biosynthesis of 937.

RESULTS

The mRNA-seq analysis and targeted pathway analysis indicated that genes associated with histidine/valine/leucine/ isoleucine/phenylalanine/tyrosine/tryptophan synthesis, galactose metabolism, purine metabolism and quorum sensing in 937 were significantly upregulated under increasing concentrations of histidine, isoleucine and glutamate in chemically defined medium (CDM). qPCR results showed that the significant upregulation of galactose metabolism- and nucleotide sugar synthesis-related genes was attributed to the increase in glutamate concentration, and glutamate could induce the expression of . The upregulation of , , and transcript levels was caused by the increase in histidine concentration. The upregulation of transcript levels of genes related to phenylalanine/tyrosine/tryptophan/histidine/ valine/leucine/isoleucine synthesis was caused by the increase in isoleucine concentrations.

DISCUSSION

This indicates that 3 amino acids have different mechanisms for enhancing the biosynthesis of f-EPS in 937.