Lactic acid bacteria reduce the toxicity of tetrodotoxin through peptidoglycan mediated binding

Tetrodotoxin (TTX) is a potent neurotoxin found in nature, the possible presence of TTX in pufferfish ovaries, liver, and other processing waste poses a serious environmental and safety hazard. Lactic acid bacteria (LAB) was found to be able to remove a variety of harmful substances, however, its elimination action and mechanism on TTX is not clear. In this study, the removal effects of different states (activated, inactivated, and fragmented LABs) of three LAB strains on TTX amount and toxicity were tested and compared. It was found that thermal inactivated LABs had the best effect, which could reduce the TTX amount by 49.0%–60.33% and decrease the toxicity of TTX by 57.0%–83.67%. In addition, peptidoglycan (PG) of three strains of LABs was found to be a key component in the removal of TTX, which could decrease the toxicity of TTX by more than 87.0 %. By analyzing the changes of functional groups of PGs, zeta-potential and binding effect between PG and TTX before and after the masking of carboxyl or amino groups of PGs, it was found that the removal effect of PG to TTX was significantly decreased (>55.0%) when the carboxyl or amino groups of PGs were masked. At the same time, the zeta-potential of PG combined with TTX was also decreased. These results suggested that the amino and carboxyl groups of PGs were important action sites for the binding interaction between LAB and TTX, and electrostatic interaction might be one of the ways of binding between PG and TTX. Our study could provide a scientific supporting on the removal action mechanism research of PG to TTX.