Biodetoxification of fungal mycotoxins zearalenone by engineered probiotic bacterium Lactobacillus reuteri with surface-displayed lactonohydrolase

Abstract

Zearalenone (ZEN) is one of the common mycotoxins with quite high occurrence rate and is harmful to animal and human health. Lactobacillus reuteri is known as a probiotic bacterium with active immune stimulating and high inhibitory activity against pathogenic microorganisms. In this study, we expressed the lactonohydrolase from Rhinocladiella mackenziei CBS 650.93 (RmZHD) in L. reuteri via secretion and surface-display patterns, respectively. Endogenous signal peptides from L. reuteri were first screened to achieve high expression for efficient ZEN hydrolysis. For secretion expression, signal peptide from collagen-binding protein showed the best performance, while the one from fructose-2,6-bisphosphatase worked best for surface-display expression. Both of the engineered strains could completely hydrolyze 5.0 mg/L ZEN in 8 h without detrimental effects on bacterial growth. The acid and bile tolerance assay and anchoring experiment on Caco-2 cells indicated both of the abovementioned engineered strains could survive during digestion and colonize on intestinal tract, in which the surface-displayed strain had a better performance on ZEN hydrolysis. Biodetoxification of model ZEN-contaminated maize kernels showed the surface-displayed L. reuteri strain could completely hydrolyze 2.5 mg/kg ZEN within 4 h under low water condition. The strain could also efficiently detoxify natural ZEN-contaminated corn flour in the in vitro digestion model system. The colonized property, survival capacity, and the efficient hydrolysis performance as well as probiotic functionality make L. reuteri strain an ideal host for detoxifying residual ZEN in vivo, which shows a great potential for application in feed industry.

Keywords: Lactobacillus reuteri; Lactonohydrolase; Surface display; Zearalenone.