Effects of fermentation with Bacillus natto on the allergenicity of peanut

Abstract

In the present study, we evaluated the immunoreactivity reduction of raw peanut pulp (RPP) by using a combination protocol of autoclave and fermentation with Bacillus natto. Assessing through an indirect ELISA, we found that the method reduced more than 77.3% of the IgE reactivity in peanut protein preparations. Further analyses with SDS-PAGE and Coomassie staining revealed that sequential autoclave and fermentation for different time caused gradually degradation of high molecular weight peanut proteins. Results from Circular dichroism and Ultraviolet absorption spectroscopies indicated that the autoclave and fermentation induced extensive proteolysis, unfolding and conformational changes, and reduction of α-helices, which all affected epitopes formation significantly. The effects of the method on peanut protein structure were further proved by the changes of surface hydrophobicity, assessed by ANS fluoresence probe, and by the alteration of free sulfhydryl groups, measured by SH-interacting DTNB. Interestingly, during the process of fermentation for 48 h, the immunoreactivity reduction of RPP was positively correlated with the content of free sulfhydryl group and negatively correlated with UV absorption intensity at 210 nm. Therefore, autoclaving assisted fermentation with Bacillus natto was an effective procedure to diminish the allergens in raw peanuts.