Insight into the protein degradation during the broad bean fermentation process

Area of Science:

• Microbiology
• Food Science
• Biochemistry

Background:

• Broad bean fermentation is essential for Pixian Douban (PXDB) production, influencing its characteristic flavor.
• Microbial protein degradation is a key step in developing PXDB's sensory profile.
• A comprehensive understanding of protein composition and degradation mechanisms during PXDB fermentation is lacking.

Purpose of the Study:

• To screen and characterize microorganisms involved in broad bean fermentation for PXDB production.
• To investigate the differential roles of fungi and bacteria in protein degradation during PXDB fermentation.
• To provide a theoretical basis for optimizing PXDB production and enhancing its quality.

Main Methods:

• Screening and identification of four key microorganisms: Aspergillus oryzae, Aspergillus jensenii, Staphylococcus gallinarum, and Enterobacter hormaeche.
• Analysis of microbial morphology, growth, enzyme production, and protease activity under varying pH conditions.
• Evaluation of protein, peptide, amino acid, and amino nitrogen content, alongside SDS-PAGE analysis of protein degradation in simulated fermentation systems.

Main Results:

• Fungal strains showed higher protease activity at neutral pH, while bacterial strains exhibited stability in neutral to acidic conditions.
• Fungal fermentation groups yielded higher total protein, peptides, and amino acids compared to bacterial groups.
• Fungal enzymes effectively degraded albumin and glutenin under neutral conditions; bacterial enzymes were more efficient under acidic conditions, as shown by SDS-PAGE.

Conclusions:

• Both fungi and bacteria significantly contribute to broad bean protein degradation during PXDB fermentation.
• Microorganisms exhibit distinct preferences for pH and substrate specificity in protein degradation.
• This research provides foundational knowledge for enhancing PXDB fermentation processes and product quality.