Effect of co-culture with Tetragenococcus halophilus on the physiological characterization and transcription profiling of Zygosaccharomyces rouxii.

Zygosaccharomyces rouxii and Tetragenococcus halophilus are widely existed and play vital roles during the manufacture of fermented foods such as soy sauce. The aim of this study was to elucidate the effect of T. halophilus CGMCC 3792 on the physiological characterizations and transcription profiling of Z. rouxii CGMCC 3791. Salt tolerance analysis revealed that co-culture with T. halophilus enhanced the salt tolerance of Z. rouxii during salt stress. Analysis of the volatile compounds revealed that co-culture reduced the level of 1-butanol, improved the level of octanoic acid which all were produced by T. halophilus and reduced the level of phenylethyl alcohol produced by Z. rouxii. The presence of Z. rouxii decreased the contents of 3,4-dimethylbenzaldehyde and acetic acid produced by T. halophilus. In addition, co-culture improved the content of benzyl alcohol significantly. Analysis of membrane fatty acid showed that co-culture improved the content of palmitic (C16:0) and stearic (C18:0) acids in cells of Z. rouxii, and reduced the contents of myristic (C14:0), palmitoleic acid (C16:1) and oleic acid (C18:1). In order to further explore the interactions between the two strains, RNA-seq technology was used to investigate the effect of co-culture with T. halophilus on the transcription profiling of Z. rouxii. By comparing cells incubated in co-culture group with cells incubated in single-culture group, a total of 967 genes were considered as differentially expressed genes (DEGs). Among the DEGs, 72 genes were up-regulated, while 895 genes were down-regulated. These DEGs took party in various activities in cells of Z. rouxii, and the result showed co-culture with T. halophilus had a positive effect on proteolysis, the attachment of a cell to another cell, extracellular protein accumulation, energy metabolism, and a negative effect on oxidative phosphorylation, small molecular substances metabolism, DNA replication and repair, and transcription in cells of Z. rouxii. Results presented in this study may contribute to further understand the interactions between Zygosaccharomyces rouxii and Tetragenococcus halophilus.