Metabolic behavior of Aspergillus oryzae in salt-reduced soy sauce and its regulation for the brewing process

Soy sauce fermentation process initiates with the involvement of Aspergillus oryzae, which serves as the primary beneficiary in salt-reduced fermentation (SRF) process. This investigation aimed to scrutinize the metabolic activities of A. oryzae in salt-reduced soy sauce and examine its subsequent impacts on the microecology and flavor profile. SRF amplified the central carbon and protein metabolism of A. oryzae, leading to improved substrate utilization efficiency, which in turn facilitated the colonization of Lactobacillus and the maintenance of a co-occurrence equilibrium within the microbiota. Consequently, Ascomycetes established a fundamental module for aroma generation, exhibiting robust interconnections. SRF facilitated A. oryzae in supplying amino acid precursors vital to produce phenylacetaldehyde derivatives. Furthermore, SRF prompted an up-regulation of the β-oxidation pathway in A. oryzae, effectively suppressing the generation of undesirable fatty rancidity odor (fatty aldehyde) derived from fatty acids. These metabolic characteristics of A. oryzae play a pivotal role in enhancing the quality of salt-reduced soy sauce.