Efficiency Evaluation and Transcriptomic Analysis of Xylooligosaccharide Utilization by Bifidobacterium pseudolongum JNFEN6

The purpose of this study was to explore the ability of different bifidobacterial species to utilize xylooligosaccharide (XOS). It focused on the mechanism for the efficient utilization of XOS by Bifidobacterium pseudolongum JNFEN6 through cell physiological analysis and transcriptomic analysis. The results showed that XOS had different effects on the growth of different Bifidobacterium species, and it had the most significant effect on the growth and acid-producing capacity of B. pseudolongum JNFEN6. When B. pseudolongum JNFEN6 was cultured for 36 h on XOS as the sole carbon source, the activity of β-xylosidase produced by this strain was 0.97 U/mL, and the concentration of propionic acid in the fermentation system was 85.26 μg/mL. The transcriptomic results showed that a total of 297 differentially expressed genes were identified, including 136 up-regulated genes and 161 down-regulated genes. Among them, the ATP-binding cassette (ABC) transport permease, substrate-binding protein and MFS transporter genes promoted the transport of XOS, while the XOS metabolic hydrolase, acetate kinase and lactate dehydrogenase genes promoted the metabolism of XOS. In summary, B. pseudolongum JNFEN6 can efficiently utilize XOS, which can take in XOS, mainly through the ABC transport system and the MFS transport system, and metabolize XOS through the ‘bifidus shunt’ pathway, finally producing short-chain fatty acids or other organic compounds. This study provides a theoretical basis for the application of XOS as a bifidus factor.