Profiling of dynamic changes in the microbial community during the soy sauce fermentation process

Area of Science:

• Food Science
• Microbiology
• Fermentation Technology

Background:

• Soy sauce flavor is critically dependent on its microbial community.
• The dynamic microbial shifts during soy sauce fermentation remain poorly understood, hindering quality control and improvement.

Purpose of the Study:

• To elucidate the dynamic changes in the microbial community during soy sauce fermentation.
• To identify key microbial players and their succession patterns.
• To provide insights for enhancing soy sauce quality.

Main Methods:

• Combined culture-dependent and culture-independent methods, including polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis.
• Analysis of bacterial and fungal communities.
• Principal component analysis (PCA) for community dynamics.

Main Results:

• Both methods confirmed significant microbial community dynamics during fermentation, with notable inhibition at the mash stage.
• Staphylococcus and Bacillus were dominant bacteria throughout; Kurthia and Klebsiella appeared transiently.
• Aspergillus sojae dominated the koji stage, while Zygosaccharomyces rouxii became dominant during mash fermentation.

Conclusions:

• The microbial community structure significantly changes early in fermentation and stabilizes later.
• Specific microbial successions, like the transition from Aspergillus sojae to Zygosaccharomyces rouxii, are crucial.
• This research provides a foundation for optimizing soy sauce fermentation for improved quality.