Insight into the protein degradation during the broad bean fermentation process

Abstract

Broad bean fermentation is of vital importance in PixianDouban (PXDB) production, as well as a key process for microorganisms to degrade protein, which lays the foundation for the formation of PXDB flavor. In this study, two fungi and bacteria were screened, and their morphology, molecular biology, growth, and enzyme production characteristics were analyzed, and then they were applied to the broad bean fermentation simulation system. The protein, peptide, amino acid, amino nitrogen, and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) in the system were evaluated. The results showed that the four microorganisms were Aspergillus oryzae , Aspergillus jensenii , Staphylococcus gallinarum , and Enterobacter hormaeche . Aspergillus oryzae had the highest protease activity at pH 7.0, while the other three strains had better enzyme activity stability under neutral acidic conditions. And the total protein (F1 and F2 were 18.32 g/100 g, 19.15 g/100 g, respectively), peptides (11.79 ± 0.04 mg/g and 12.06 ± 0.04 mg/g), and amino acids (55.12 ± 2.78 mg/g and 54.11 ± 1.97 mg/g) of the fungus experimental groups (F) were higher than the bacterial experimental groups (B). In addition, the enzyme system produced by fungi exhibited a stronger ability for albumin (20 kDa) and glutenin (<30 kDa) deterioration in neutral conditions, while the bacterial enzyme system was more efficient in degrading albumin (<30 kDa) and glutenin (20–30 kDa) in acidic conditions, as indicated by SDS‐PAGE. These findings showed that both bacteria and fungi played an important role in the degradation of protein in different fermentation stages of broad bean fermentation. Practical applications There is a lack of comprehensive understanding of the protein composition and protein degradation mechanism of broad beans in the fermentation stage of PXDB. This research work explored the differences in the degradation of PXDB fermented protein by different microorganisms, and provided a theoretical basis for optimizing the production of PXDB and improving the quality of PXDB.

Partial substitution of wheat flour with soybean and gluten powder: impact on flavor characteristics of Pixian Douban‐Meju and its quality

“…Organic acids have a strong influence on flavor balance, chemical stability, pH, and sample quality 6 . As shown in Fig.…”

“…Organic acids have a strong influence on flavor balance, chemical stability, pH, and sample quality. 6 As shown in Fig. 3, a total of seven acids (including oxalic acid, tartaric acid, malic acid, lactic acid, citric acid, fumaric acid, and succinic acid) were detected.…”

“…Wheat flour with a protein content of 10% (3–5% water‐soluble protein and 40–50% alcohol‐soluble protein) accounts for 20–30% of the meju, and is an important nutrient for microbial growth and a vital precursor for the formation of aromatic and flavor substances in the PXDB 4,5 . Previous studies have shown that the degradation of alcohol‐soluble protein mainly occurred in the early stages of PXDB fermentation (0–30 days), and the degradation of water‐soluble protein mainly occurred in the later stages of PXDB fermentation (after 30 days) 6 …”

“…4,5 Previous studies have shown that the degradation of alcohol-soluble protein mainly occurred in the early stages of PXDB fermentation (0-30 days), and the degradation of watersoluble protein mainly occurred in the later stages of PXDB fermentation (after 30 days). 6 During the meju fermentation stage, the proteins are hydrolyzed by microorganism proteases, peptidases, and glutaminases to produce polypin-tides and free amino acids (FAAs). 7 These hydrolysates contribute to the fresh, sweet, bitter, and salty taste, and the color of PXDB, which directly affected the flavor of the final products.…”

Microbial-derived salt-tolerant proteases and their applications in high-salt traditional soybean fermented foods: a review

“…Bacterial strains have significantly higher protease and peptidase activity compared to yeast and molds (Zhou et al 2021 ). However, simulations of the fermentation of broad bean paste by two salt-tolerant fungi and two salt-tolerant bacteria have shown that the total protein, peptide, and amino acid content is higher in the fungal group than in the bacterial group (Lin et al 2022 ). Fungal-derived enzyme systems have demonstrated greater albumin and glutenin activity under neutral conditions.…”