Structure characterization, antioxidant capacity, rheological characteristics and expression of biosynthetic genes of exopolysaccharides produced by Lactococcus lactis subsp. lactis IMAU11823

Exopolysaccharides (EPSs) from lactic acid bacteria have special functions and complex structures, but the function and structure of EPSs of the important dairy starter, Lactococcus (L.) lactis subsp. lactis, are less known. This study investigated the cytotoxicity, antioxidant capacities, rheological characteristics, chemical structure and expression of biosynthetic genes of EPSs of the L. lactis subsp. lactis IMAU11823. The EPSs showed strong reducing power and no cytotoxicity. EPS-1 comprised glucose and mannose (molar ratio of 7.01: 1.00) and molecular weight was 6.10 x 10(5) Da, while EPS-2 comprised mannose, glucose and rhamnose (7.45: 1.00: 2.34) and molecular weight was 2.93 x 10(5) Da. EPS-1 was a linear structure comprised two sugar residues, while EPS-2 was more complex, non-linear, and comprised eight sugar residues. In additions, our study proposed an EPS biosynthesis model for the IMAU11823 strain. The current findings have broadened the understanding of the formation, structure and function of complex EPSs of IMAU11823.

Automated summary

Exopolysaccharides (EPSs) from Lactococcus lactis subsp. lactis IMAU11823 were found to have strong reducing power and no cytotoxicity. The EPSs had different sugar compositions and molecular weights, with EPS-1 being a linear structure composed of glucose and mannose, and EPS-2 being a more complex, non-linear structure composed of mannose, glucose, and rhamnose. Furthermore, a biosynthesis model for EPS production in the IMAU11823 strain was proposed. This study broadens the understanding of the formation, structure, and function of complex EPSs produced by Lactococcus lactis subsp. lactis IMAU11823.