Degradation of aflatoxin B1 by membrane reactor attached with hairpin-like structured peptide enzyme mimics

Aflatoxins, particularly aflatoxin B1 (AFB1), are extremely powerful toxins with carcinogenic, teratogenic, and mutagenic effects that accumulate through the food chain and pose serious health risks. Developing simple, low-cost and biocompatible strategies for AFB1 degradation is of great scientific significance. Based on the ability of S/H/E catalytic triads to effectively cleave ester bonds, five hairpin-like structured peptides were designed for AFB1 degradation. The -V^DPPL- site within the peptides bends the peptide chain to form a rigid hairpin-like "U" shape with a hydrophobic cavity that captured the substrate AFB1 through hydrogen bond and van der Waals interactions. Effects of the self-assembled peptide fiber structure and the location of catalytic triad on enzyme mimics activity were investigated. The proton transfer unit formed within the S/H/E catalytic triad was found to be effective during dissociation of the lactone bond of AFB1, which resulted in ring opening and toxin degradation. Among the peptides investigated, the sequence EHSVKLKV^DPPLDVHLSHE (P3) exhibited the highest catalytic activity toward AFB1 degradation. Finally, a membrane reactor for AFB1 degradation was prepared by attaching P3 onto a cellulose membrane. This membrane reactor can be mounted in a flow system to degrade AFB1 in real samples, such as soy milk, soy sauce and corn juice with a degradation efficiency of approximately 90%. The technique developed in this work might be utilized to remove AFB1 in food process on line.