Oyster, as a common aquatic food, play an important role in shellfish allergy. In this study, two tropomyosin (TM) isoforms TM-α and TM-β (TM-α/-β) in Alectryonella plicatula were identified. The sequences of 852 bp encoding 284 amino acids of TM-α/-β and two recombinant proteins were obtained, respectively. There were 12 amino acid differences between TM-α/-β. The results of immunological experiments indicated that TM-β had stronger immunobinding activity and immunoreactivity than those of TM-α. Structural analysis showed that TM-β had more α-helix and higher surface hydrophobicity than TM-α. Sequences and epitopes alignment with shellfish TMs revealed that amino acids of TM-β were more frequently recognized as IgE epitopes in other shellfish TMs than TM-α. Differences in structure and sequence account for the higher immunological activity of TM-β compared to TM-α. These findings provide a theoretical basis for enriching the understanding of shellfish TM and accurate diagnosis of allergic components.

In recent years, the allergy rate of oysters has surged, and daily food processing methods make it hard to reduce heat resistance and digestive allergy such as tropomyosin (TM). In this study, the Maillard reaction with xylose significantly reduced the IgE binding capacity of Alectryonella plicatula food matrix (AFM), that reduced by (77.81 ± 2.68)%. The study found the Maillard reaction changes the structure of the AFM, in which the content of α-helix decreased by (24.64 ± 1.46)%. Structural transformation further explains why the Maillard reaction alters the immunobinding activity of AFM. In addition, the Maillard reaction reduces the digestive stability of the AFM and makes tropomyosin (TM) in the A. plicatula food matrix Maillard reaction products (AFM-MRPs) more easily digested. Based on the above research, 10 amino acids on the 7 IgE epitopes of TM were modified. This result indicates that the Maillard reaction reduces the immunobinding activity of the AFM by changing the structure and modifying the amino acids on the epitope.

Bacteria contamination in Auricularia auricular culture bags reduces yield and increases the risk of food safety. In this study, 5 species of bacteria, mainly gram-positive bacteria including three species of Bacillus spp., Arthrobacter arilaitensis and Staphylococcus warneri, were isolated and identified from bacteria-contaminated A. auricular culture bags. An in silico predicted antimicrobial peptide from the β-1,3-glucan-binding protein sequence of Penaeus vannamei, designated PvGBP2 (FLKLGRKSRYGMLKL), was screened and its antibacterial effect and mechanism of action on the isolated Bacillus spp. explored. The minimal inhibitory concentrations (MIC) of PvGBP2 on Bacillus spp. were 15.6–31.25 μg/mL. Peptide PvGBP2 could inhibit Bacillus subtilis in A. auricular culture bags to maintain growth and yield of A. auricular. Transmission electron microscopy (TEM) revealed that PvGBP2 kills bacteria by perforating the cell wall, destroying membrane integrity and resulting in the leakage of intracellular solutes. In addition, PvGBP2 inhibits biofilm formation by B. subtilis by 90.6% at 1 × MIC. Thus, peptide PvGBP2 could be potentially applied as an antibacterial agent to control bacterial infection of A. auricular cultivation and the spread of foodborne pathogens.