Effect Of Lactiplantibacillus Plantarum Fermentation On The Allergenicity Of Siberian Apricot Kernel Protein

Siberian apricot kernels contain a variety of nutrients and bioactive substances,which have high application value in food production and pharmaceutical industry.However,as one of the eight main allergenic food,tree nuts pose a threat to the health of allergic patients and their future applications were effected.This article selected six commonly used strains in food fermentation and processing,and Lactiplantibacillus plantarum FSB7 was selected with the best fermentation effect for hydrolyzing Siberian apricot kernel protein.Its optimal fermentation conditions to reduce the allergenicity of Siberian apricot kernel was determined.The changes in the structural properties and allergenic epitopes of Siberian apricot kernel protein after fermentation was also explored,providing a theoretical basis for future research on low allergenic Siberian apricot kernel products.In this study,six common strains in fermentation production: Lactobacillus thermophilus HH-ST08,Bifidobacterium brevis M-16 V,Lactobacillus brevis CICC 6239,Lactobacillus bulgaricus HH-IB57,Lactiplantibacillus plantarum ACCC 11095,Lactiplantibacillus plantarum FSB7 were used for liquid fermentation of Siberian apricot kernel samples.The fermentation effects of various strains on protein hydrolysis of Siberian apricot kernel were compared through the determination of free amino acid content,protein hydrolysis degree and SDS-PAGE.The results showed that Lactiplantibacillus plantarum FSB7 was the most suitable strain for fermenting and hydrolyzing Siberian apricot kernel protein.After 24 hours of fermentation,the free amino acid contents increased by more than four times,and the degree of hydrolysis reached 82.0%.The resultes of SDS-PAGE showed the bands at the large molecular positions were significantly weakened and new bands appeared at the small molecular positions.In summary,Lactiplantibacillus plantarum FSB7 was the strain among the six strains that could achieve the best hydrolysis effect in a short period of time.And the stability of Siberian apricot kernel milk fermented by six different strains was measured.Among the four strains with higher fermentation hydrolysis degree,the decrease in the stability coefficient of Siberian apricot kernel milk fermented by Lactiplantibacillus plantarum FSB7 was relatively small,which was declined to 59.5% of the unfermented apricot kernel milk.Finally,it was determined that among the six strains,Lactiplantibacillus plantarum FSB7 was the most suitable strain for fermenting Siberian apricot kernel protein.Next,the optimal conditions for Siberian apricot kernel protein fermentation by Lactiplantibacillus plantarum FSB7 were explored using single-factor experiments.The fermentation time of the sample,the ratio of fermentation material to water,the initial p H and the inoculum amount of the strain were changed respectively,and the effect of the hydrolysis of Siberian apricot kernel protein was determined by measuring the change of p H,the content of small peptides,the degree of hydrolysis,and the change of SDS-PAGE during the fermentation process.The optimal fermentation conditions were ultimately determined as follows: fermentation time of 36 hours,material water ratio of 1:20(m/v),initial p H = 6.5,and inoculation amount of 0.1%(v/m).After fermentation,the p H of Siberian apricot kernel sample decreased to 3.50,the highest degree of hydrolysis reached to 90.1%,and the small peptide content reached to 3.38%.The electrophoresis bands at the 36 k Da,38 k Da,22 k Da,and 20 k Da macromolecular positions before fermentation became weakened or even disappeared,and new bands appeared at smaller molecule positions.The optimal fermentation conditions of Lactiplantibacillus plantarum FSB7 were used to treat Siberian apricot kernel samples,the immunogenicity changes were determined using indirect enzyme-linked immunosorbent assay.Ultimately,the immunogenicity of Siberian apricot kernel after fermentation was decreased to 20.9% of unfermented samples,indicating that Lactiplantibacillus plantarum FSB7 fermentation could effectively destroy the allergenic protein of Siberian apricot kernel.The structural changes of Siberian apricot kernel protein after fermentation were investigated by using ANS fluorescence probe method,fluorescence spectroscopy,Ellman method,circular dichroism,and other methods.The results showed that the free sulfhydryl content increased to 0.77 mmol/mg after fermentation,which was 2.48 times higher than the0.33 mmol/mg of the unfermented sample.The ANS fluorescence intensity and hydrophobicity index of Siberian apricot kernel protein showed a trend of first increasing and then decreasing with the prolongation of fermentation time,but overall they were significantly higher than those of unfermented samples,indicating that Lactiplantibacillus plantarum fermentation improved the hydrophobicity of Siberian apricot kernel protein.The circular dichroism results showed an increase in the irregular curl content of Siberian apricot kernel protein.These structural changes are the potential reasons for the reduced allergenicity of Siberian apricot kernel protein.Finally,the hydrolysis of fermentation on the linear epitope of Siberian apricot kernel protein was explored.The fermented Siberian apricot kernel samples were purified and desalted by gel chromatography.After the components were separated by the preparation stage liquid phase,the peptide hydrolyzed peptide sequence was analyzed by LC-MS/MS and compared with the amino acid sequence in the NCBI database to analyze the destruction of the linear epitope of Siberian apricot kernel protein.The results showed that there were broken linear epitopes of Siberian apricot kernel allergen determined in the peptide sequence after fermentation hydrolysis,which proved that the linear epitopes of fermented Siberian apricot kernel allergen after Lactiplantibacillus plantarum FSB7 were destroyed.In conclusion,Siberian apricot kernel can be fermented and hydrolyzed by Lactobacillus plantarum FSB7 effectively and the protein structure were changed.The structural and linear epitope of Siberian apricot kernel allergen protein were destroyed,which significantly reduced its allergenicity.